Canada’s Oceans Now: Atlantic Ecosystems, 2018

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Table of Contents

Foreword

Canada’s Oceans Now reports are annual summaries of the current status and trends in Canada’s oceans. These reports for Canadians are part of the Government of Canada’s commitment to inform its citizens on the current state and potential future state of Canada’s oceans.

Canada’s Oceans Now: Atlantic Ecosystems provides the current status and trends in Atlantic Canada’s marine ecosystems up to the end of 2017. This report is based on the scientific synthesis reportFootnote 1 which was presented at a science meeting in December 2017. The synthesis report includes summaries of the available peer-reviewed literature and data on aspects of the physical and chemical oceanography, biological oceanography, habitats, fish and invertebrate communities, marine mammals, sea turtles, and seabirds. Fisheries and Oceans Canada (DFO) scientists and colleagues from Environment and Climate Change Canada (ECCC) contributed peer-reviewed and published data from monitoring and research programs for this report. This information will be updated in future reports to create an ongoing picture of the status and trends of Atlantic Canada’s marine ecosystems.

Introduction

Understanding the health of the marine environment is vitally important to an ocean nation like Canada. The surrounding Atlantic, Arctic, and Pacific oceans support all Canadians. Every Canadian shares a deep connection with these dynamic marine ecosystems. Our oceans support everyday recreation and tourism, cultural and spiritual pursuits, and the health of Canadians. They are an important source for food and natural resources across the country. On a larger scale, all life on our planet is affected by the oceans’ role in regulating global climate, nutrient cycling, and biodiversity.

Marine ecosystems include the physical and chemical environment along with a vast array of living organisms, from tiny plankton to giant whales. These ecosystems are varied, complex, and naturally dynamic. But the added impacts of human activities and climate change are causing changes to occur. These changes can have serious impacts on the health of marine ecosystems.

Climate change is a key driver of the changes observed within the Atlantic Ocean environment. Rising atmospheric temperatures are having effects that include warmer sea-surface temperatures, less sea ice cover, rising sea levels, and changing ocean currents. Increased absorption of carbon dioxide by sea-surface water is leading to ocean acidification. Understanding the interconnections of these diverse components can be challenging. However, this knowledge is more important than ever.

As an ocean nation, Canada has a responsibility to study and protect these marine ecosystems. Government scientists regularly monitor and conduct research on the oceans to track the status and trends occurring over time.

This report looks at what scientists know about the Atlantic Ocean environment. From sea-surface temperature to fish population numbers, it summarizes the overall health and state of Canada’s Atlantic Ocean.

Atlantic Canada’s three ocean zones

The Canadian Atlantic Ocean is divided into three bioregions: the Newfoundland and Labrador Shelves (NL), the Scotian Shelf (SS), and the Gulf of St. Lawrence (GSL) (Figure 1). Each bioregion is based on geographic differences in ocean conditions and depth and has distinct characteristics. However, the boundaries between them are transition zones, not abrupt borders.

The Canadian Atlantic Ocean is heavily influenced by seasonal changes in currents, water temperature, sea ice, and freshwater runoff. Seasonal changes in sea ice, particularly on the Newfoundland and Labrador Shelves and the Gulf of St. Lawrence, influence freshwater input and the timing of phytoplankton blooms. The Labrador Current brings cool Arctic water along the Newfoundland and Labrador Shelves (Figure 2). This is the southernmost penetration of Arctic waters in the Northern Hemisphere. The southern part of the Scotian Shelf is warmed by Gulf Stream water from the south. The mixing of these two flows creates a key area of high productivity along the tail of the Grand Banks of Newfoundland that supports regional ecosystems. The Gulf of St. Lawrence has significant freshwater input from the St. Lawrence River that mixes with waters from the Atlantic: Labrador Shelf waters through the Strait of Belle Isle and a mixture of cold Labrador Current water and warm Gulf Stream water from the Cabot Strait.

Figure 1: Three Bioregions of Atlantic Canada – Bioregion locations are based on ocean conditions and depth. Northwest Atlantic Fisheries Organization (NAFO) sub-divisions are boundaries used for science and management of various marine resources and are used throughout the report. A map of the Canadian Atlantic highlighting three Atlantic bioregions with different coloured shapes.  The Newfoundland and Labrador Shelves bioregion is blue, the Scotian Shelf bioregion is orange, and the Gulf of St. Lawrence bioregion is dark pink. Boundaries of the Northwest Atlantic Fisheries Organization (NAFO) sub-divisions are shown in the waters off the Atlantic coast as polygons bordered by white dashed lines. Each NAFO area has a number and letter to indicate their name. A legend sits on the left of the map indicating bioregions and NAFO areas. The location of cities mentioned in the report are shown with black dots across the map – Saint John, NB; Fredericton, NB; Quebec City, QC; Rimouski, QC; Sept-Iles, QC, Harrington Harbour, QC;  St. John’s, NL; Charlottetown, PEI; Halifax, NS.

Figure 1: Three Bioregions of Atlantic Canada – Bioregion locations are based on ocean conditions and depth. Northwest Atlantic Fisheries Organization (NAFO) sub-divisions are boundaries used for science and management of various marine resources and are used throughout the report.

Figure 2: Currents of the Canadian Atlantic – Two main current systems influence the Canadian Atlantic – the cold Labrador Current from the north (darker blue), and the warm Gulf Stream from the south (dark red). A map of the Canadian Atlantic highlighting current systems in the water. A thick dark red line with an arrow at the end represents the Gulf Stream flowing north and east of North America. A dark blue line with an arrow at the end represents the Labrador Current flowing south from Baffin Island and Greenland. An orange current indicates Irminger Current which is shown on the south end of Greenland. Smaller blue lines with arrows are spread across the map to indicate various currents of the Canadian Atlantic.

Figure 2: Currents of the Canadian Atlantic – Two main current systems influence the Canadian Atlantic – the cold Labrador Current from the north (darker blue), and the warm Gulf Stream from the south (dark red).

The Ocean Environment

Changes in the physical environment have important impacts on biological systems at different scales. For example, warming temperatures caused by climate change can have impacts on individual organisms, such as changes in species growth rates or at larger scales such as changes in food webs.

Oceanographers have measured ocean conditions off the Atlantic coast for decades. This wealth of data is being used to understand the links between the environment and ecosystems. It is also used to assess the impacts of human activities. Two major Fisheries and Oceans Canada programs collect data on ocean conditions. The Atlantic Zone Monitoring Program (AZMP) and the Atlantic Zone Offshore Monitoring Program (AZOMP) study the physical, chemical, and biological properties on the continental shelves and slopes off Canada’s east coast.

During monitoring and research surveys, sampling devices known as rosettes are deployed down through the water column. The sensors they carry can measure physical and chemical variables such as temperature, dissolved oxygen and acidity. They also carry bottles to collect water samples at different depths. These samples can be analyzed onboard the ship or onshore in a lab. This information, combined with other sources of data like satellite imaging, gives a bigger picture of the health of the ocean. Environmental conditions are usually reported in a way that shows how they differ from long-term averages. These differences are known as anomalies. For temperature from remote sensing, these anomalies are generally calculated in relation to the average temperature over the period of 1985–2010 and 1981-2010 for other oceanographic parameters.

Temperature

The waters of the North Atlantic are temperate, as they get both cold and warm depending on the season. Surface water temperatures vary with air temperature. Deeper waters do not show much seasonal change but are instead influenced by currents. An important interaction is the mixing of cooler, fresher water from the Labrador Current and the warmer, saltier waters of the Gulf Stream.

Rising air temperatures driven by climate change and changes in currents are leading to warmer temperatures at both the sea-surface and deep waters (Figure 3, Figure 4). Temperature is an important environmental factor. It influences everything from physical processes (such as sea ice formation and mixing of the water column) to the condition and behaviour of the species that live there.

Scientists measure water temperatures through the water column using automated sensors and direct measurements on research surveys. They also interpret satellite information. Sea-surface temperature from remote sensing is reported for ice-free periods of the year. These periods vary annually and regionally (from the north to south).

Status and trends

Figure 3: Index of sea surface temperature for the Atlantic bioregions measured during ice-free times of the year. These values are relative to the 1985-2010 average. The black trend line represents the combined anomalies for all areas (eGoM: eastern Gulf of Maine; BoF: Bay of Fundy; see Figure 1 for NAFO Divisions). Above average trends are warm conditions. A combined line and bar graph illustrates the fluctuations in sea surface temperature between 1985 and 2017 for the three Atlantic bioregions. Text above the graph says “Sea-surface temperature”. The vertical axis at left shows numbers from -25 to 25 in increments of 5 with a thin black zero-line extending across the graph. Text left of the vertical axis and above the zero-line says “above average” and text under the zero-line says “below average”. The horizontal axis shows years between 1980 to 2015 in 5 year increments. A legend sits at right showing the colours for areas within each bioregion illustrated as stacked bars on the graph. Areas within the Newfoundland and Labrador Shelves are in shades of blue, areas within the Gulf of St. Lawrence are in shades of pink, and areas within the Scotian Shelf are in shades of orange. A thick black line extends between the vertical and horizontal axes showing the combined trend of temperature for all areas, with temperatures going from below average in the late 1980s and early 1990s to generally being above average in the 1990s. The trend is consistent in most areas.

Figure 3: Index of sea surface temperature for the Atlantic bioregions measured during ice-free times of the year. These values are relative to the 1985-2010 average. The black trend line represents the combined anomalies for all areas (eGoM: eastern Gulf of Maine; BoF: Bay of Fundy; see Figure 1 for NAFO Divisions). Above average trends are warm conditions.

Figure 4: Index of ocean bottom temperatures for the Atlantic bioregions relative to the long-term average (1981-2010). The black trend line represents the combined anomalies for all areas (nGSL: northern Gulf of St. Lawrence; see Figure 1 for NAFO Divisions). Above average trends are warm conditions.  Shifts in currents have brought record highs since 2012. A combined line and bar graph illustrates the fluctuations in ocean bottom temperature between 1980 and 2017 for the three Atlantic bioregions. Text above the graphs says “Ocean bottom temperature”. The vertical axis at left shows numbers from -25 to 25 in increments of 5, with a thin black zero-line extending across the graph. Text left of the vertical axis and above the zero-line says “above average” and text under the zero-line says “below average”. The horizontal axis shows years between 1980 and2015 in 5 year increments. A legend sits at right showing the colours for areas within each bioregion illustrated as stacked bars on the graph. Areas within the Newfoundland and Labrador Shelves are in shades of blue, areas within the Gulf of St. Lawrence are in shades of pink, and areas within the Scotian Shelf are in shades of orange. A thick black line extends between the vertical and horizontal axes showing the combined trend of temperature, with temperatures being above average in the 2010s. Text reading “Record highs since 2012” floats above the line on the graph on the right-hand side.

Figure 4: Index of ocean bottom temperatures for the Atlantic bioregions relative to the long-term average (1981-2010). The black trend line represents the combined anomalies for all areas (nGSL: northern Gulf of St. Lawrence; see Figure 1 for NAFO Divisions). Above average trends are warm conditions. Shifts in currents have brought record highs since 2012.

Sea Ice and cold intermediate layer

Seasonal changes in sea ice and the layers in the water column play important roles in the way North Atlantic ecosystems function. An important feature in this region is the cold intermediate layer (CIL). The CIL forms in some areas when the winter cold mixed layer is trapped by spring surface warming, along with freshwater from sea ice melt and runoff from land, forming a less dense layer at the top of the water column [See: Stratification and the cold intermediate layer]. In some areas, the layering may persist for most of the year. Since sea ice cover and the CIL both form in winter, they often relate to each other as well as with winter air temperature. The data are therefore combined as one index (Figure 5). The CIL influences mixing within the water column. This affects how nutrients are distributed, which has an impact on the productivity of ecosystems.

Seasonal changes in sea ice, particularly on the Newfoundland and Labrador Shelves and the Gulf of St. Lawrence, influence freshwater input and the timing of phytoplankton blooms (See Phytoplankton Section). Sea ice also provides habitat for organisms that live under and on the ice.

Sea ice cover is monitored by the Canadian Ice Service (ECCC) using aerial surveys and satellite imaging, providing important factors such as the maximum extent of sea ice into southern areas and its timing. Estimates of the coverage, thickness, and volume of ice are also made.

Status and trends

  • Climate change is leading to less sea ice cover in Atlantic marine ecosystems. Warmer winters since the late 1800s have led to generally longer periods without ice and lower ice volume.
  • During the past decade, ice volumes on the Newfoundland and Labrador Shelves, the Gulf of St. Lawrence, and the Scotian Shelf have been lower than average in most years. They reached a record low in the Gulf of St. Lawrence in 2010 and on the Newfoundland and Labrador Shelves in 2011.
  • For the period between 2010-2016, 3 years were among the 7 lowest average sea ice volumes ever observed on the Newfoundland and Labrador Shelves. In the Gulf of St. Lawrence, 5 years were among the 7 lowest average sea ice volumes ever observed.
  • Warmer winters are leading to weaker CILs. In 2012, there were record lows for CIL volumes in both the Gulf of St. Lawrence and Scotian Shelf, representing record warm conditions.
Figure 5: Index of cold intermediate layer (CIL) and sea ice volume for the Atlantic bioregions relative to the long-term average (1981-2010). The black trend line represents the combined anomalies for all areas (sGSL: southern Gulf of St. Lawrence; see Figure 1 for NAFO Divisions). Above average trends are seen when warming conditions lead to less sea ice and a weak CIL. A combined line and bar graph illustrates the fluctuations in the index of cold intermediate layer (CIL) and sea ice volume for the Atlantic bioregions between 1980 and 2017 for the three Atlantic bioregions. Text above the graph says “Sea ice and CIL”. The vertical axis at left shows numbers from -20 to 20 in increments of 5, with a thin black zero-line extending across the graph. Text left of the vertical axis and above the zero-line says “above average” and text under the zero-line says “below average”. The horizontal axis shows years between 1980 and 2015 in 5 year increments. On the left-hand side of the graph, text above the zero line says “warmer than average” and text below the zero-line says “colder than average”. A legend sits at right showing the colours for areas within each bioregion illustrated as stacked bars on the graph. Areas within the Newfoundland and Labrador Shelves are in shades of blue, areas within the Gulf of St. Lawrence are in shades of pink, and areas within the Scotian Shelf are in shades of orange. A thick black line extends between the vertical and horizontal axes showing the combined trend, with the line being generally below average in the early 1990s and then above average after the late 1990s. On the right-hand side of the graph, text reading “Record lows for sea ice” floats above the trend line near 2010. Below the zero-line on the right-hand side of the graph, a line of text reads “Record low CILs in 2012” with an arrow pointing at 2012.

Figure 5: Index of cold intermediate layer (CIL) and sea ice volume for the Atlantic bioregions relative to the long-term average (1981-2010). The black trend line represents the combined anomalies for all areas (sGSL: southern Gulf of St. Lawrence; see Figure 1 for NAFO Divisions). Above average trends are seen when warming conditions lead to less sea ice and a weak CIL.

Stratification and the cold intermediate layer

The ocean becomes stratified because layers of water with different densities make mixing of the water column more difficult (Figure 6). During fall and winter, cooling and wind cause mixing and homogenization of the upper layers of the ocean. In the spring and summer, surface waters become less dense because of warming and increased freshwater from melting sea ice and runoff from land. This less dense water does not easily mix into the denser, cooler, deep water leading to stratification. A cold intermediate layer (CIL) forms as cold, winter water is trapped under this less dense surface layer. In some shallower areas, the CIL may extend all the way to the bottom, but in others a third deep, denser layer remains. The water temperature used to define the CIL is different between the bioregions. On the Newfoundland and Labrador Shelf it is <0℃, in the Gulf of St. Lawrence it is <1℃, and on the Scotian Shelf it is <4℃.

Figure 6 Stratification of the ocean is influenced by temperature, the input of freshwater from land and sea ice melt, and energy for mixing from wind and currents which change seasonally. An illustration shows a cross section view of the ocean, extending from a coastal river to an estuary and out to the continental shelf. Text at the top of the graphic says “Stratification and the cold intermediate layer”. The land is illustrated in a light brown colour. It starts with a flat shelf then slopes out under the water and flattens out again. Three stacked layers of water are shown in different shades of blue. On the left-hand side, an arrow points down with vertical text saying “depth”. The top layer of water is light blue and text on the right-hand side says “less dense”. Outside the graphic on the right, a light blue triangle extends from the top layer to text which says “Surface Layer”. The middle layer is dark blue and on the right-hand side, three lines of text say “NL <0°C”, “Gulf <1°C”, and “SS<4°C”. Outside the graphic on the right, a dark blue triangle extends from the middle layer to text which says “Cold Intermediate Layer”. The bottom layer near the ocean floor is blue and text on the right-hand side says “Denser”. Outside the graphic on the right, a blue triangle extends from the top layer to text which says “Deep Layer”. From the left-hand side and extending towards the centre of the surface layer, four arrows point to the right. In the middle layer, on the left-hand side, three black arrows point upwards on an angle to the left. On the right-hand side of the graphic, overlapping the top, middle and bottom layers, there is a circle made of three arrows going clockwise. Text in the circle reads “Mixing occurs in fall/winter”.

Figure 6 Stratification of the ocean is influenced by temperature, the input of freshwater from land and sea ice melt, and energy for mixing from wind and currents which change seasonally.

Oxygen

Figure 7: Average dissolved oxygen, pH (acidity) and temperature measurements for the lower St. Lawrence Estuary at approximately 300 metres. Values of dissolved oxygen below 30% saturation are considered extremely hypoxic. Three vertically stacked line graphs representing oxygen (top), acidity (pH) (middle) and temperature (bottom) of the Lower St. Lawrence Estuary. Text above the graph says “Dissolved oxygen, acidity (pH), and temperature in the Lower St. Lawrence Estuary (300m). All three line graphs share the same horizontal axis which shows years between 1940 and 2020 in 20 year increments. Data begins in 1932 and extends to 2017 with some large gaps particularly between 1940 and 1960. The first line graph illustrates fluctuations in oxygen levels. The vertical axis at left shows numbers between 50 and150 in increments of 25 with text that reads “Dissolved Oxygen (micro-mols per litre) and a dashed horizontal line extending horizontally from the number 100. Above this line, on the right-hand side of the graph, text reads “Approx. 30% saturation” and below text reads “Hypoxic conditions”. A teal data line shows oxygen levels over time. There is some data in the 1930s and 1960s to 1970s which is generally above the hypoxic line while data since the 1980s is below the hypoxic line. The second line graph illustrates fluctuations in pH. The vertical axis at left shows numbers between 7.5 and 8.0 in increments of 0.1 with text that reads “pH”. A pink data line shows pH levels over time There are two points of data in the 1930s which are between 7.8 and7.9. There is no data from 1940 to 1980, but from 1980 to 2017 the data has a general downward trend from approximately 7.7 to almost 7.5. On the right-hand side, text above the line between 2000 and 2020 reads “Increasing acidity”. The third line graph illustrates fluctuations in temperature levels. The vertical axis at left shows numbers between 3 and 6 in increments of one with text that reads “Temperature (°C)”. A light blue line shows temperature levels over time. Data in the 1930s is just above 3°C and there is a a general upwards trend across the graph with values near 5.5°C in 2017. Text above the line between 200 and 2020 reads “Warming conditions”.

Figure 7: Average dissolved oxygen, pH (acidity) and temperature measurements for the lower St. Lawrence Estuary at approximately 300 metres. Values of dissolved oxygen below 30% saturation are considered extremely hypoxic.

The amount of dissolved oxygen in seawater is important for the health of marine organisms. In deep water, mixing from the surface waters can replace oxygen. When there is little mixing, dissolved oxygen can be depleted by the respiration of organisms and the breakdown of organic matter. When oxygen levels are too low, the condition is called hypoxia. When oxygen levels fall below 30 percent of the maximum they can hold, it is considered severely hypoxic. This can have serious effects on ecosystems. Changes in climate can contribute to hypoxia occurring. So too can the input of organic matter from algal blooms caused by high levels of nutrients. This has been a problem in the Gulf of St. Lawrence (Figure 7).

Hypoxia can dramatically affect marine life and ecosystems. It can slow growth and reduce reproductive success among ocean species. It can also impact the way species are distributed, as most species leave an area before hypoxia can kill them. With severe hypoxia, species that cannot move fast enough out of the affected area can suffer high mortality rates.

Dissolved oxygen is regularly measured throughout the water column as part of oceanographic surveys done within the region.

Status and trends

Acidification

Ocean acidity is increasing as the ocean absorbs ever-greater amounts of atmospheric carbon dioxide from human activities. Carbon dioxide dissolves in the surface ocean water to form carbonic acid. An increase in acidity makes the water more corrosive to calcium carbonate, the main element of the skeletons and shells of many organisms including plankton, molluscs, crustaceans, and corals. Increases in acidity can also cause increased physiological stress for these organisms. These changes can have implications for food webs and ecosystems as a whole.

Acidity has been measured consistently since the 1990s. Intermittent measurements extend back to the 1930s. Acidity is measured on the pH scale [See pH]. Lower pH indicates more acidic conditions and higher pH indicates less acidic conditions (Figure 7).

Status and trends

Runoff and stratification

Figure 8: Water column stratification measured as the difference between the density of water at the surface and water at 50m depth. The estimate for the St. Lawrence estuary is based on fresh water runoff. A large difference in density, such as shown here in the St. Lawrence Estuary, means more stratification and potentially inhibited mixing. On the Scotian Shelf and Newfoundland and Labrador Shelves the difference is lower. There is lower stratification in these areas. A line graph illustrates the fluctuations in stratification for the three Atlantic bioregions. Above the graph text reads “Stratification Trends”. The vertical axis at left shows numbers from 0 to 6 in increments of one with text that reads “Density difference 0-50m (kg per metre cubed). The horizontal axis shows years between 1960 to 2020 in 20 year increments. A legend sits at right showing bioregional colours for sample areas used in the graph. Three coloured data lines show trends in stratification over time. A blue line representing Newfoundland and Labrador Shelves fluctuates over time between 0 and 1.5 kg per metre cubed. A yellow line representing the Scotian Shelf fluctuates over time between 0 and 2 kg per metre cubed, just above the blue line. A dashed pink line represents an estimate for the St. Lawrence Estuary (Rimouski) from 1946 to 2008 and a red line represents the St. Lawrence Estuary data from 1990 to 2017. These lines fluctuate between 3 and 6 kg per metre cubed.

Figure 8: Water column stratification measured as the difference between the density of water at the surface and water at 50m depth. The estimate for the St. Lawrence estuary is based on fresh water runoff. A large difference in density, such as shown here in the St. Lawrence Estuary, means more stratification and potentially inhibited mixing. On the Scotian Shelf and Newfoundland and Labrador Shelves the difference is lower. There is lower stratification in these areas.

The circulation and mixing of the ocean can be impacted by runoff from the land especially in areas that receive large amounts of runoff, like the St. Lawrence Estuary. Layering called stratification can form in the water column because waters with different densities don’t mix very easily [See: Stratification and the cold intermediate layer]. Freshwater runoff from the land can increase stratification, since fresher water is less dense than saltier water. Along with tides and wind, runoff drives the circulation within the St. Lawrence Estuary and, to a lesser extent, in the whole Gulf of St. Lawrence.

Ocean stratification can affect the way nutrients are mixed into surface waters. A change in nutrient mixing influences phytoplankton growth and blooms. This, in turn, impacts ecosystem productivity.

The amount of stratification in the water column is measured by looking at the difference in density between water at the surface and water at a depth of 50 metres. Long-term trends are reported for three locations: Station 27 (a site off St. John’s, Newfoundland and Labrador), Rimouski Station in the St. Lawrence Estuary, and the Scotian Shelf. Year to year, stratification at the Rimouski Station is strongly related to the seasonal average runoff of the St. Lawrence River (Figure 8).

Status and trends

Sea level

Figure 9: Sea level difference for locations across the Atlantic bioregions between 1890 and 2011. The values are relative to the average for 1981-2010 in each area (See Figure 1 for locations.). Glacial melt along with ocean warming is causing sea level to rise in many areas along the Atlantic coast at a rate of 2 to 4 mm/year while falling in others. Six line graphs representing the relative sea level of various cities in Atlantic Canada are stacked vertically. Text above the graph says “Relative sea level difference (cm)”. All six graphs have the same vertical axis which shows numbers between -30 and 10 in increments of 10. A vertical line of text to the left of the graphs extends across the set of graphs and reads “Sea level difference relative to 1980-2010 avg (cm)”. Each graph also has a dashed line extending horizontally across the graph at zero. All six line graphs share the same horizontal axis which shows years between 1890 and-2010 in 30 year increments. Overall the data extends from 1895 to 2011, but not all graphs have the same length of data. The first line graph illustrates fluctuations in sea level for Charlottetown, PEI. A pink data line shows sea level difference from 1910 to 2010, with small gaps in the data before the late 1930s. Sea level increases from approximately -30cm and crosses the zero-line after 1990. The second line graph illustrates fluctuations in sea levels for Harrington Harbour, QC. A red data line shows sea level difference from 1940 to 1988, with sea level hovering around the zero-line. The third line graph illustrates fluctuations in sea levels for Quebec City, QC. A dark pink data line shows sea level difference from 1911-2011 with a gap between 1911 and the 1930s. Sea level gfluctuates around the zero-line. The fourth line graph illustrates fluctuations in sea levels for Halifax, NS. A dark yellow data line shows sea level difference with two data points in the mid-1890s near -30cm, and a continuous record from 1920 to 2011 which increasesand crosses the zero-line after 1990. The fifth line graph illustrates fluctuations in sea levels for Saint John, NB. A light yellow data line shows sea level difference from 1896-2011 with some gaps before 1940. Sea level increases across the graph from near -20cm and crosses the zero-line after 1990. The sixth line graph illustrates fluctuations in sea levels for St John’s, NL. A teal blue data line shows sea level difference from 1936 to 2011 with large gaps to the 1950s Sea level increases across the graph from near -20cm and fluctuates around the zero-line after 1990.

Figure 9: Sea level difference for locations across the Atlantic bioregions between 1890 and 2011. The values are relative to the average for 1981-2010 in each area (See Figure 1 for locations.). Glacial melt along with ocean warming is causing sea level to rise in many areas along the Atlantic coast at a rate of 2 to 4 mm/year while falling in others.

As the world’s oceans become warmer and glaciers melt due to increasing global temperatures, the volume of seawater rises. In some areas, this is offset to some extent because the land is still rising after the removal of the weight of ice following the end of the last ice age. This means that some areas will experience rising sea levels while others will experience falling sea levels (Figure 9).

Sea level rise can degrade habitat or lead to its loss in coastal areas. It also makes coastal areas more vulnerable to storm surges. This can impact the distribution of important habitat-forming species such as eelgrass and kelp.

Changes in sea level are measured using tide gauges and satellite measurements. In some areas, data are available from the late 1800s. For others, data starts in the mid-1900s. The trends are reported in relation to the average sea level measurements for 1981–2010 in each area.

Status and trends

Nutrients

Like plants on land, phytoplankton require light and nutrients to grow. The most important nutrients include nitrogen (nitrates, nitrites, and ammonium), phosphorous (phosphate), and silica (silicate). Nitrogen is usually the limiting nutrient for the growth of phytoplankton in the ocean. This means that it is usually present in lower concentrations in surface water than other nutrients. As a result, nitrogen cycling within the water column is very important.

The size of the spring phytoplankton bloom is partly dependent on the amount of nutrients that are mixed into surface waters during the winter. In fall, a secondary bloom that is less intense than the spring bloom can occur. This happens when nutrients are mixed from deep water into surface waters that were depleted during the summer. Since phytoplankton form the base of many marine food webs, the size of the spring bloom is linked to the overall productivity of these ecosystems.

Nutrients are regularly measured through the water column as part of oceanographic surveys within the Atlantic region. Nitrogen is reported as the “deep water nitrate inventory” (Figure 10). This represents nitrate concentrations present in deeper water, which at some time may be mixed through the water column to become available to phytoplankton.

Status and trends

  • Changes in nitrate were not uniform in all parts of the Atlantic. Over the last five years, conditions well below the long-term average were often observed in many parts of the Northwest Atlantic.
  • The greatest declines, which persisted until 2014–2015, occurred on the Newfoundland Shelf.
  • Conditions in the Gulf of St. Lawrence and Scotian Shelf had more moderate shifts over time. However, most recently nutrient levels in the Gulf and on the Scotian Shelf are near and below average, respectively.
  • Nitrate inventories in deep water are highly variable. However, they have been largely at average levels from 2012 to 2016 after a general declining trend from 1999 to 2010.
Figure 10: Index of nitrate concentrations measured in deep waters between 50-150m depth. These values are relative to the long-term average (1999-2010). The black trend line represents the combined anomalies for all areas (See Figure 1 for NAFO Divisions). Above average trends are higher concentrations. The levels of nitrate impact the spring bloom which is linked to the productivity of other species. A combined line and bar graph illustrates the fluctuations in the index of deep water nitrate concentrations between 1999 and 2016 for the three Atlantic bioregions. Text above the graph says “Deep nitrate inventory (50-150m)”. The vertical axis at left shows numbers from -20 to 20 in increments of 5, with a thin black zero-line extending across the graph. Text left of the vertical axis and above the zero-line says “above average” and text under the zero-line says “below average”. The horizontal axis shows years between 1999 and 2016 in 5 year increments. A legend sits at right showing the colours for areas within each bioregion illustrated as stacked bars on the graph. Areas within the Newfoundland and Labrador Shelves are in shades of blue, areas within the Gulf of St. Lawrence are in shades of red, and areas within the Scotian Shelf are in shades of orange. The combined index of nitrate concentrations is shown by a thick black line that extends between the vertical and horizontal axes. Text reading “Record highs since 2012” floats above the line on the graph on the right-hand side. There is variability in the overall trend and between regions, but the overall trend was generally below average in the last five years.

Figure 10: Index of nitrate concentrations measured in deep waters between 50-150m depth. These values are relative to the long-term average (1999-2010). The black trend line represents the combined anomalies for all areas (See Figure 1 for NAFO Divisions). Above average trends are higher concentrations. The levels of nitrate impact the spring bloom which is linked to the productivity of other species.

Life in the Atlantic

Canada’s Atlantic waters are one of the most productive marine environments in the world. Marine communities consist of a variety of organisms from microscopic phytoplankton, which form the base for marine food webs, to fish and invertebrate species including important commercial species (e.g. Atlantic cod, snow crab, American lobster), and some of the largest mammals found on Earth such as the blue whale. These organisms live in a wide variety of habitats. In coastal areas, structured habitats such as eelgrass beds and kelp forests, all provide important feeding resources for other organisms, shelter from predators, and nursery areas for young. Cold-water corals and sponges in the deep offshore provide more complex habitat on the sea floor, which many species depend on for shelter and food. The Northwest Atlantic is also an important feeding area for many migratory species, including turtles, whales, and seabirds.

Scientific observations have revealed that these ecosystems are experiencing both physical and biological changes at different rates and scales across the Atlantic region. The distribution of species is shifting and communities are changing. All species in this marine ecosystem have experienced changes, from phytoplankton and other marine plants to invertebrate and fish communities, to marine mammals and seabirds. Changes are also occurring in habitats experiencing stress. This places additional negative impacts on species. Climate change is one of the key drivers of these changes. Other human activities that have an impact include fishing, coastal development, and resource exploitation.

Phytoplankton

Figure 11: Index of Chlorophyll a concentrations relative to the long-term average (1999-2010). These values are used to indicate the biomass of phytoplankton. The black trend line represents the combined anomalies for all areas (See Figure 1 for NAFO Divisions). Above average values represent higher concentrations. In most of the region, phytoplankton biomasses have been well below average since 2015. A combined line and bar graph illustrates the fluctuations in the index of chlorophyll a concentrations relative to the long-term average (1999-2010) between 1999 and 2016 for the three Atlantic bioregions. Text above the graph says “Chlorophyll a inventory (0-100m)”. The vertical axis at left shows numbers from -20 to 20 in increments of 5 with a thin black zero-line extending across the graph. Text left of the vertical axis and above the zero-line says “above average” and text under the zero-line says “below average”. The horizontal axis shows years between 1999 to 2016 in one year increments. A legend sits at right showing the colours for areas within each bioregion illustrated as stacked bars on the graph. Areas within the Newfoundland and Labrador Shelves are in shades of blue, areas within the Gulf of St. Lawrence are in shades of pink, and areas within the Scotian Shelf are in shades of orange. At the bottom of the graph on the left-hand side a line of text says “low chlorophyll a = less phytoplankton”. A thick black line extends between the vertical and horizontal axes showing the combined trend of the index of chlorophyll a concentrations for all areas. The overall trend is below average since 2015 with some variability between areas.

Figure 11: Index of Chlorophyll a concentrations relative to the long-term average (1999-2010). These values are used to indicate the biomass of phytoplankton. The black trend line represents the combined anomalies for all areas (See Figure 1 for NAFO Divisions). Above average values represent higher concentrations. In most of the region, phytoplankton biomasses have been well below average since 2015.

Phytoplankton are microscopic plants that produce oxygen and organic matter from sunlight, carbon dioxide, and inorganic nutrients, like plants on land. Phytoplankton increase in abundance (or bloom) in the spring, and to a lesser extent, in the fall. Blooms can occur when the water column is stable, so phytoplankton can remain near the surface where light levels are high, and nutrients are available.

Phytoplankton support many marine food webs as the key food source for zooplankton, that are in turn food for many fish and marine mammals. Phytoplankton abundance is an indicator of how productive a system is. Changes in the timing of the spring bloom can have consequences for many other organisms in the ecosystem.

Through direct sampling and satellite imagery, scientists measure “chlorophyll a” in the surface ocean. Chlorophyll a is the main pigment used in photosynthesis. These measurements are used to represent the biomass and productivity of phytoplankton in the ocean. The more chlorophyll a that is detected, the more phytoplankton cells are assumed to be in the water (Figure 11). The magnitude, peak time, and duration of the blooms are assessed by looking at changes in the chlorophyll a concentrations (Figure 12a, Figure 12b, Figure 12c). This provides information on how the entire system changes from year to year. [See: Crucial links between climate and marine productivity].

Status and trends

Figure 12: Observations of the spring phytoplankton bloom including indexes of a) magnitude, b) peak time, and c) duration. All are relative to the long-term average (1998 to 2010). The black trend lines represent the combined anomalies for all areas (See Figure 1 for NAFO Divisions).A group of three graphs illustrate observations of the spring phytoplankton blooms for the three Atlantic bioregions including indexes of a) magnitude, b) peak time, and c) duration compared to the long-term average (1998-2010). Each graph is a combined line and bar graph. A thick black line illustrates the combined trend for all areas on each graph. A legend sits at the right showing the colours for areas within each bioregion illustrated as stacked bars on each graph. Areas within the Newfoundland and Labrador Shelves are in shades of blue, areas within the Gulf of St. Lawrence are in shades of pink, and areas within the Scotian Shelf are in shades of orange. Text above the first graph, labelled “a”, says “Magnitude of spring bloom”. The vertical axis at left shows numbers from -30 to 40 in increments of 5 with a thin black zero-line extending across the graph. Text left of the vertical axis and above the zero-line says “above average” and text under the zero-line says “below average”. On the left-hand side of the graph, text near the top says “more intense bloom” and text near the bottom says “less intense bloom”. The horizontal axis shows years between 1998 and 2016 in one year increments. A thick black line extends between the vertical and horizontal axes showing the combined trend of the index of spring bloom magnitude for all areas. There is variability between areas, but the overall trend increases between 1999 and 2011 and then decreases towards the zero-line. A line of text near the above the trend line towards the centre of the graph says “Increased 1999-2011”.

Figure 12: Observations of the spring phytoplankton bloom including indexes of a) magnitude, b) peak time, and c) duration. All are relative to the long-term average (1998 to 2010). The black trend lines represent the combined anomalies for all areas (See Figure 1 for NAFO Divisions).

Figure 12: Observations of the spring phytoplankton bloom including indexes of a) magnitude, b) peak time, and c) duration. All are relative to the long-term average (1998 to 2010). The black trend lines represent the combined anomalies for all areas (See Figure 1 for NAFO Divisions).A group of three graphs illustrate observations of the spring phytoplankton blooms for the three Atlantic bioregions including indexes of a) magnitude, b) peak time, and c) duration compared to the long-term average (1998-2010). Each graph is a combined line and bar graph. A thick black line illustrates the combined trend for all areas on each graph. A legend sits at the right showing the colours for areas within each bioregion illustrated as stacked bars on each graph. Areas within the Newfoundland and Labrador Shelves are in shades of blue, areas within the Gulf of St. Lawrence are in shades of pink, and areas within the Scotian Shelf are in shades of orange. Text above the second graph, labelled “b”, says “Peak time of spring bloom”. The vertical axis at left shows numbers from -50 to 40 in increments of 5 with a thin black zero-line extending across the graph. Text left of the vertical axis and above the zero-line says “above average” and text under the zero-line says “below average”. On the left-hand side of the graph, text near the top says “later peak bloom” and text near the bottom says “earlier peak bloom”. The horizontal axis shows years between 1998 and 2016 in one year increments. A thick black line extends between the vertical and horizontal axes showing the combined trend of the index of spring bloom peak time for all areas. There is variability between areas, but the overall trend goes below the zero-line in the early 2010s and then increases above the zero-line after 2013.

Figure 12: Observations of the spring phytoplankton bloom including indexes of a) magnitude, b) peak time, and c) duration. All are relative to the long-term average (1998 to 2010). The black trend lines represent the combined anomalies for all areas (See Figure 1 for NAFO Divisions).

Figure 12: Observations of the spring phytoplankton bloom including indexes of a) magnitude, b) peak time, and c) duration. All are relative to the long-term average (1998 to 2010). The black trend lines represent the combined anomalies for all areas (See Figure 1 for NAFO Divisions).A group of three graphs illustrate observations of the spring phytoplankton blooms for the three Atlantic bioregions including indexes of a) magnitude, b) peak time, and c) duration compared to the long-term average (1998-2010). Each graph is a combined line and bar graph. A thick black line illustrates the combined trend for all areas on each graph. A legend sits at the right showing the colours for areas within each bioregion illustrated as stacked bars on each graph. Areas within the Newfoundland and Labrador Shelves are in shades of blue, areas within the Gulf of St. Lawrence are in shades of pink, and areas within the Scotian Shelf are in shades of orange. Text above the second graph, labelled “c”, says “Duration time of spring bloom”. The vertical axis at left shows numbers from -25 to 30 in increments of 5 with a thin black zero-line extending across the graph. Text left of the vertical axis and above the zero-line says “above average” and text under the zero-line says “below average”. On the left-hand side of the graph, text near the top says “longer bloom” and text near the bottom says “shorter bloom”. The horizontal axis shows years between 1998 and 2016 in one year increments. A thick black line extends between the vertical and horizontal axes showing the combined trend of the index of spring bloom duration for all areas. There is variability between areas, but the overall trend goes decreases from 1998 to 2011 going below the zero-line in the early 2000s. It then stayed around the zero line until a large peak in 2016. A line of text above the bars to the right of centre on the graph says “Record duration in 2016” and an arrow points to the last year of data.

Figure 12: Observations of the spring phytoplankton bloom including indexes of a) magnitude, b) peak time, and c) duration. All are relative to the long-term average (1998 to 2010). The black trend lines represent the combined anomalies for all areas (See Figure 1 for NAFO Divisions).

Zooplankton

Zooplankton are small animals that drift in the water column, feeding on phytoplankton, bacteria, and fungi. They range in size from 0.2 mm to 20 mm. Zooplankton community structure is strongly influenced by water depth, temperature, and season. Communities differ substantially among the three Atlantic bioregions. Copepods are the most abundant zooplankton species in the western North Atlantic. One of the largest, most widespread, abundant, and energy-rich zooplankton species is the copepod Calanus finmarchicus. Smaller copepods known as Pseudocalanus spp. are less energy-rich, but they are studied as a way of representing all of the smaller species in the community.

Zooplankton are a critical link between phytoplankton and larger marine animals. Because C. finmarchicus is both abundant and nutritious, changes in its abundance have important consequences for animals that rely on it as a primary food source.

On research surveys, zooplankton are collected by net tows. The tows help determine the abundance and species types of zooplankton. Abundances are reported for total zooplankton, C. finmarchicus, Pseudocalanus spp., and non-copepod species. Monitoring these four levels has been found to provide a good indication of the health of zooplankton communities across the Atlantic bioregions (Figure 13a, Figure 13b, Figure 13c, Figure 13d).

Status and trends

Figure 13:  Observations of zooplankton abundances including indexes for a) <em>Calanus finmarchicus</em>, b) <em>Pseudocalanus</em> spp., c) total copepod species, and d) non-copepod species. All are relative to the long-term average (1999-2010). The black trend lines represent the combined anomalies for all areas (See Figure 1 for NAFO Divisions). A group of four graphs illustrate observations of zooplankton abundances for the three Atlantic bioregions including indexes of a) Calanus finmarchicus, b) Pseudocalanus spp., c) total copepod species, and d) non-copepod species compared to the long-term average (1999-2010). Each graph is a combined line and bar graph. A thick black line illustrates the combined trend for all areas on each graph. A legend sits at the right showing the colours for areas within each bioregion illustrated as stacked bars on each graph. Areas within the Newfoundland and Labrador Shelves are in shades of blue, areas within the Gulf of St. Lawrence are in shades of pink, and areas within the Scotian Shelf are in shades of orange. Text above the first graph, labelled “a”, says “Calanus finmarchicus abundance”. The vertical axis at left shows numbers from -35 to 15 in increments of 5 with a thin black zero-line extending across the graph. Text left of the vertical axis and above the zero-line says “above average” and text under the zero-line says “below average”. The horizontal axis shows years between 1999 and 2016 in one year increments. A thick black line extends between the vertical and horizontal axes showing the combined trend of the index of Calanus finmarchicus abundance for all areas. There is variability between areas, but the overall trend is around the zero-line in the 2000s until 2009 when it begins to decline and remains below the zero-line. A line of text below the trend line towards the centre of the graph says “Declining numbers since 2009”.

Figure 13: Observations of zooplankton abundances including indexes for a) Calanus finmarchicus, b) Pseudocalanus spp., c) total copepod species, and d) non-copepod species. All are relative to the long-term average (1999-2010). The black trend lines represent the combined anomalies for all areas (See Figure 1 for NAFO Divisions).

Figure 13:  Observations of zooplankton abundances including indexes for a) <em>Calanus finmarchicus</em>, b) <em>Pseudocalanus</em> spp., c) total copepod species, and d) non-copepod species. All are relative to the long-term average (1999-2010). The black trend lines represent the combined anomalies for all areas (See Figure 1 for NAFO Divisions). A group of four graphs illustrate observations of zooplankton abundances for the three Atlantic bioregions including indexes of a) Calanus finmarchicus, b) Pseudocalanus spp., c) total copepod species, and d) non-copepod species compared to the long-term average (1999-2010). Each graph is a combined line and bar graph. A thick black line illustrates the combined trend for all areas on each graph. A legend sits at the right showing the colours for areas within each bioregion illustrated as stacked bars on each graph. Areas within the Newfoundland and Labrador Shelves are in shades of blue, areas within the Gulf of St. Lawrence are in shades of pink, and areas within the Scotian Shelf are in shades of orange. Text above the second graph, labelled “b”, says “Pseudocalanus spp. abundance”. The vertical axis at left shows numbers from -20 to 30 in increments of 5 with a thin black zero-line extending across the graph. Text left of the vertical axis and above the zero-line says “above average” and text under the zero-line says “below average”. On the left-hand side of the graph, text near the top says “later peak bloom” and text near the bottom says “earlier peak bloom”. The horizontal axis shows years between 1998 and 2016 in one year increments. A thick black line extends between the vertical and horizontal axes showing the combined trend of the index of Pseudocalanus spp. Abundance for all areas. There is variability between areas, but since 2013 the overall trend has increased above the zero-line at the highest level of the time period of the graph. A line of text above the trend line on the right-hand side of the graph says “Recent record high numbers”.

Figure 13: Observations of zooplankton abundances including indexes for a) Calanus finmarchicus, b) Pseudocalanus spp., c) total copepod species, and d) non-copepod species. All are relative to the long-term average (1999-2010). The black trend lines represent the combined anomalies for all areas (See Figure 1 for NAFO Divisions).

Figure 13:  Observations of zooplankton abundances including indexes for a) <em>Calanus finmarchicus</em>, b) <em>Pseudocalanus</em> spp., c) total copepod species, and d) non-copepod species. All are relative to the long-term average (1999-2010). The black trend lines represent the combined anomalies for all areas (See Figure 1 for NAFO Divisions). A group of four graphs illustrate observations of zooplankton abundances for the three Atlantic bioregions including indexes of a) Calanus finmarchicus, b) Pseudocalanus spp., c) total copepod species, and d) non-copepod species compared to the long-term average (1999-2010). Each graph is a combined line and bar graph. A thick black line illustrates the combined trend for all areas on each graph. A legend sits at the right showing the colours for areas within each bioregion illustrated as stacked bars on each graph. Areas within the Newfoundland and Labrador Shelves are in shades of blue, areas within the Gulf of St. Lawrence are in shades of pink, and areas within the Scotian Shelf are in shades of orange. Text above the second graph, labelled “c”, says “Total copepods abundance”. The vertical axis at left shows numbers from -15 to 30 in increments of 5 with a thin black zero-line extending across the graph. Text left of the vertical axis and above the zero-line says “above average” and text under the zero-line says “below average”. On the left-hand side of the graph, text near the top says “later peak bloom” and text near the bottom says “earlier peak bloom”. The horizontal axis shows years between 1998 and 2016 in one year increments. A thick black line extends between the vertical and horizontal axes showing the combined trend of the index of Pseudocalanus spp. Abundance for all areas. There is variability between areas, but since the overall trend is around the zero-line until 2013 when it increases to values higher than the rest of the time period. A line of text above the trend line on the right-hand side of the graph says “Higher than average since 2014”.

Figure 13: Observations of zooplankton abundances including indexes for a) Calanus finmarchicus, b) Pseudocalanus spp., c) total copepod species, and d) non-copepod species. All are relative to the long-term average (1999-2010). The black trend lines represent the combined anomalies for all areas (See Figure 1 for NAFO Divisions).

Figure 13:  Observations of zooplankton abundances including indexes for a) <em>Calanus finmarchicus</em>, b) <em>Pseudocalanus</em> spp., c) total copepod species, and d) non-copepod species. All are relative to the long-term average (1999-2010). The black trend lines represent the combined anomalies for all areas (See Figure 1 for NAFO Divisions). A group of four graphs illustrate observations of zooplankton abundances for the three Atlantic bioregions including indexes of a) Calanus finmarchicus, b) Pseudocalanus spp., c) total copepod species, and d) non-copepod species compared to the long-term average (1999-2010). Each graph is a combined line and bar graph. A thick black line illustrates the combined trend for all areas on each graph. A legend sits at the right showing the colours for areas within each bioregion illustrated as stacked bars on each graph. Areas within the Newfoundland and Labrador Shelves are in shades of blue, areas within the Gulf of St. Lawrence are in shades of pink, and areas within the Scotian Shelf are in shades of orange. Text above the second graph, labelled “d”, says “Non-copepod abundance”. The vertical axis at left shows numbers from -15 to 30 in increments of 5 with a thin black zero-line extending across the graph. Text left of the vertical axis and above the zero-line says “above average” and text under the zero-line says “below average”. On the left-hand side of the graph, text near the top says “later peak bloom” and text near the bottom says “earlier peak bloom”. The horizontal axis shows years between 1998 and 2016 in one year increments. A thick black line extends between the vertical and horizontal axes showing the combined trend of the index of Pseudocalanus spp. Abundance for all areas. There is variability between areas, but since the overall trend is around the zero-line until 2010 when it rises above the zero-line and then increases again in 2014 to peak in 2015 at values higher than the rest of the time period. A line of text above the trend line on the right-hand side of the graph says “Record highs since 2014”.

Figure 13: Observations of zooplankton abundances including indexes for a) Calanus finmarchicus, b) Pseudocalanus spp., c) total copepod species, and d) non-copepod species. All are relative to the long-term average (1999-2010). The black trend lines represent the combined anomalies for all areas (See Figure 1 for NAFO Divisions).

Crucial links between climate and marine productivity

Timing is important when it comes to the relationship between phytoplankton, zooplankton, and the forage fish that feed on them. That timing depends on winter and spring climatic conditions.

Small pelagic (open water dwelling) fish like Atlantic herring and capelin are major prey for larger marine predators like Atlantic cod, Greenland Halibut, seabirds, and marine mammals. These prey fish are also called forage fish.

Recent studies on the Newfoundland and Labrador Shelves have provided insight into how climate affects the capelin population. A key factor is the timing of melting sea ice in spring that generates ocean conditions that are favourable to the spring bloom of phytoplankton. If blooms occur too early, due to early ice retreat, zooplankton may miss the maximum peak of phytoplankton production. This creates a “mismatch” in energy flow, and reduces zooplankton productivity. The result is lower forage fish production. Capelin and herring production are linked directly with the abundance of their zooplankton prey. Capelin growth and spawning may be directly impacted by poor zooplankton production.

In turn, capelin availability has been shown to be an important driver of the abundance of the northern Atlantic cod stock and reproductive rates in harp seals.

These “bottom up” processes connect spring phytoplankton blooms to zooplankton abundance and the performance of forage fish which impacts organisms higher in the food web (Figure 14).

Figure 14: Spring ice retreat is important for creating conditions favourable for the spring phytoplankton bloom. When the timing of spring ice retreat causes a “mismatch” between spring bloom and peak zooplankton production, this leads to low productivity of zooplankton and in capelin which feed on them. This impacts the availability of  food for species higher up the food web. Two similar illustrations of a simple Atlantic marine ecosystem food web, stacked vertically. The first illustration has a title at top left that reads “Average spring bloom. Match”. On the bottom left side of the illustration there is a circular image of sea ice with text above it that reads “Sea ice retreat”. An orange arrow points up to the right to a circular image of phytoplankton with text above it that reads “Spring bloom/phytoplankton”. An orange arrow points right to text that reads “Match” and a circular image of several zooplankton with text above it that reads “zooplankton”. An orange arrow points right to an orange circle surrounding a school of capelin with text to the right that reads “capelin are important prey for other species”. Three orange arrows point down from the orange capelin circle. One arrow on the left points to a group of seals with the text “marine mammals”, the second in the middle points to an image of several fish with the text “large fish” and the third on the right points to a flock of seabirds with the text “sea birds”. The second illustration has a title at top left that reads “Early/late spring bloom. Mismatch”. On the bottom left side of the illustration there is a circular image of sea ice with text above it that reads “Late or early sea ice retreat”. An orange arrow points up to the right to a circular image of phytoplankton with text above it that reads “Spring bloom/phytoplankton”. An orange arrow points right to text that reads “Mismatch” and a circular image of one zooplankton with text above it that reads “zooplankton”. An orange arrow points right to an orange circle surrounding a few shaded capelin with text to the right that reads “Fewer capelin means less food for other species”. Three orange arrows point down from the orange capelin circle. One arrow on the left points to a few shaded seals with the text “marine mammals”, the second in the middle points to an image of one shaded fish with the text “large fish” and the third on the right points to two small shaded seabirds with the text “sea birds”.

Figure 14: Spring ice retreat is important for creating conditions favourable for the spring phytoplankton bloom. When the timing of spring ice retreat causes a “mismatch” between spring bloom and peak zooplankton production, this leads to low productivity of zooplankton and in capelin which feed on them. This impacts the availability of food for species higher up the food web.

Intertidal Flats

Intertidal flats are dynamic environments that are submerged by seawater during high tide and exposed to air during low tide. The various sizes of soft-sediment types (categorized by grain size) that form these intertidal flats provide habitat for a diversity of marine organisms living above and below the surface. These include many species of worms, molluscs, crustaceans, shorebirds, and fishes.

Intertidal flats are ecologically and economically important habitats. This habitat supports major food sources for resident and migratory shorebirds. They also support large densities of clams and worms that are harvested commercially and recreationally. Of all the intertidal flats in Atlantic Canada, some of the most important are the mudflats of the Bay of Fundy. These mudflats support high densities of infaunal animals (animals living within sediments) that support the migration of millions of shorebirds each year. Extreme environmental conditions may impact marine organisms that inhabit intertidal flats. These include warming temperatures, ocean acidification, and eutrophication.

Both the abundance of organisms and the organic content of sediments need to be studied at the same time, since they can both indicate environmental issues in intertidal flats. Sediment samples are extracted and are examined for grain size and organic matter. Biological samples can be collected using core samplers, shovels, underwater pumps and sieves. These samples are used to measure biodiversity and abundance of infaunal animals. Other sampling techniques can include nets for fish, pitfall traps for animals living on top of the sediment, and recording observations or banding for shorebirds. Probes that record environmental parameters such as oxygen, carbon dioxide, temperature, and salinity can also be used to examine the chemistry of the sediment.

Status and trends

Eelgrass beds

Eelgrass is a marine flowering plant that forms extensive underwater meadows. Eelgrass can tolerate large fluctuations in salinity and temperature. However, these plants require shallow, clear water to photosynthesize and establish healthy, well-developed root systems to survive. Eelgrass beds are indicators of ecosystem health because they respond to changing environmental conditions quickly. For example, eelgrass will die when they are covered by nuisance algae in waters polluted with too many nutrients. They also die off quickly if water temperatures are too high.

Eelgrass filters water, stabilizes sediments, and acts as a shoreline buffer. It also provides nursery and feeding habitat for some commercial and recreational fish such as Atlantic cod and white hake [See: Eelgrass: An Ecologically Significant Species]. Small invertebrates also eat bacteria and other organisms growing on eelgrass blades and in the sediments.

Close monitoring of eelgrass beds can provide timely evidence of environmental change. Eelgrass distribution can be mapped using aerial photography, satellite imaging, LIDAR remote sensing, and local knowledge. Plant health can be measured by counting shoots, measuring leaf length, measuring biomass of leaves and shoots, and sampling chemicals within the leaves.

Status and trends

Eelgrass: An Ecologically Significant Species

Figure 15: One year old Atlantic cod over eelgrass habitat in Newman Sound, Terra Nova Park, Newfoundland and Labrador. Source: DFO diving group. An underwater photograph of bright green eelgrass with small one year Atlantic cod swimming in the eelgrass.

Figure 15: One year old Atlantic cod over eelgrass habitat in Newman Sound, Terra Nova Park, Newfoundland and Labrador. Source: DFO diving group.

It seems a straight forward idea that young fish in nursery habitats will grow, mature, and ultimately support adult populations, including those important to commercial fisheries. However, linking juvenile and adult abundance can be difficult because fish tend to move to different habitats as they grow. Juvenile Atlantic cod for example, are found in high densities in coastal vegetated habitats including seagrass and algal beds. As they grow, cod spread out to occupy various coastal and offshore habitats that are deeper and less vegetated where younger fish do not live. Variation in the environment from year to year can also make comparisons between juvenile and adult populations hard.

A very important coastal nursery habitat for juvenile cod is eelgrass (Figure 15). It is considered an Ecologically Significant Species (ESS) because of the relative significance of its influence supporting coastal habitat for juvenile fish such as Atlantic cod.

Eelgrass beds are some of the most productive nursery habitats in the world. They provide protection and food for juvenile cod, which supports their abundance, survival, and growth.

Research on eelgrass and cod has been carried out in Newman Sound, Bonavista Bay, Newfoundland and Labrador throughout the past 23 years. It shows a link between the density of 1-year old Atlantic cod before leaving eelgrass nursery habitats and pre-adult cod about to enter the commercial fishery. Changes in the abundance of 1-year old cod are linked to similar increases and decreases in the abundance of adult cod years later.

This link illustrates the importance of coastal nursery habitats such as eelgrass to healthy adult populations. Better quality habitat will produce more juvenile cod and subsequently more adult cod. Therefore, factors that can negatively impact eelgrass, such as European green crab, will adversely impact cod populations.

Kelp beds

Kelp are large, brown algae species that form dense forests in rocky, shallow subtidal zones. Kelp need cold water to flourish and are particularly susceptible to changes in temperature. Warmer waters reduce kelp growth rates, may cause death, and encourage the growth of invasive biofouling species (See Aquatic Invasive Species Section), such as the European Coffin Box bryozoan. This colonial biofouling invertebrate forms crusts on the surface of kelp. It can cause breakage in heavy surf conditions due to increased tissue brittleness, and limit the capacity of kelp to photosynthesize and reproduce. Destruction of entire kelp forests in Nova Scotia have been attributed to the spread and establishment of the Coffin Box bryozoan.

Kelp beds are very productive. Fish use them for feeding, protection from predators, and as nursery grounds. Atlantic cod, white hake, American lobster, rock crab, and Jonah crab are commercial fishes and crustaceans that use kelp beds during juvenile stages or throughout their lifetimes. In addition to providing critical fish habitat, kelp beds move organic material to deeper offshore waters, which fuels food webs. Kelp also play a role in oceanic carbon storage and cycling.

Kelp are monitored using historical observational data and ongoing research studies.

Status and trends

Corals and sponges

Figure 16: Left: Map of significant benthic areas (SiBAs) and vulnerable marine ecosystems (VMEs) for sponges, sea pens, large and small gorgonian corals on the east coast of Canada. SiBAs are identified by DFO within the 200nm Exclusive Economic Zone (EEZ) boundary while VMEs are outside the EEZ as identified by NAFO.  Right: Examples of sponges, sea pens, large and small gorgonians found in the Canadian Atlantic. Corals and sponges tend to be distributed in the cold waters along the edges of the continental shelf down to 3000 metres depth. They are very vulnerable to human activities. A map of the Canadian Atlantic illustrating the locations of significant benthic areas (SiBAs) and vulnerable marine ecosystems (VMEs) for sponges, sea pens, large and small gorgonian corals. The map shows Baffin Island and Greenland in the north and eastern Canada and the United States in the south out into the central Atlantic. On the left and right sides of the map, tick marks show the 40°N, 50°N, and 60°N latitude lines, and on the bottom of the map, tick marks show the 70°W, 60°W, 50°W, and 40°W longitude lines. A scale bar appears at the bottom right corner of the map. The land masses on the map are coloured beige and the water is white. Text on the land identifies “Canada”, “USA”, and “Greenland”. A legend appears at the right-hand side outside the map. Sponges, sea pens, large gorgonians, and small gorgonians are represented by different colour outlines on the map. For each category, the legend has one or two photos and coloured circles of the corresponding category colour. Solid lines represent “Significant Benthic Areas (SiBAs) – DFO” and dashed lines represent “Vulnerable Marine Ecosystems (VMEs) – NAFO”. Above the top row of the legend there is text saying “Sponges”. Underneath there are two small photos with text saying “Vazella pourtalesi” and “Rosellidae sp.” respectively. The outlines representing sponges are purple. Above the second row there is text saying “Sea pens”. Underneath there are two small photos with text saying “pennatula sp.” and “Halipteris finmarchia” respectively. The outlines representing sea pens are yellow. Above the third row there is text saying “Large gorgonians”. Underneath there are two small photos with text saying “Keratoisis grayi” and “Paragorgia arborea” respectively. The outlines representing large gargonians are red. Above the fourth row there is text saying “Small gorgonians”. Underneath there is one small photo with text saying “Acanella arbuscula” respectively. The outlines representing large gargonians are green. The 1500m bathymetric contour of the shelf is outlined with a thin blue line. On the east coast of Canada, it outlines the Scotian Shelf and the Newfoundland and Labrador Shelves. North in the Labrador Sea It curves south of Baffin Island and then goes right around the tip of Greenland. Also indicated by a thin black line on the map is the Exclusive Economic Zone (EEZ) of Canada which is 200nm off the coast. Outlined areas within the EEZ are solid indicating SiBAs and outside they are dashed to indicating VMEs. The outlines for areas of corals and sponges are located mainly along the edge of the shelf along the 1500m bathymetric contour. There are also more outlined areas running between Nova Scotia and Newfoundland and within the Gulf of St. Lawrence which are mainly purple and yellow indicating areas of sponges and sea pens.

Figure 16: Left: Map of significant benthic areas (SiBAs) and vulnerable marine ecosystems (VMEs) for sponges, sea pens, large and small gorgonian corals on the east coast of Canada. SiBAs are identified by DFO within the 200nm Exclusive Economic Zone (EEZ) boundary while VMEs are outside the EEZ as identified by NAFO. Right: Examples of sponges, sea pens, large and small gorgonians found in the Canadian Atlantic. Corals and sponges tend to be distributed in the cold waters along the edges of the continental shelf down to 3000 metres depth. They are very vulnerable to human activities.

Corals grow mainly on stable bottoms such as boulders and bedrock but can also anchor in soft sediments. The distribution of deep-water corals is patchy, influenced by the condition of the seabed, temperature, salinity, and currents. Sponges are found along continental shelves, slopes, canyons and deep fjords, at depths down to 3,000 metres (Figure 16). Both deep-sea corals and sponges are highly vulnerable to human activities, like fishing and resource extraction. Corals may also be vulnerable to the effects of climate change as some species can only survive at certain temperatures.

Corals and sponges may be the only complex habitat-forming features on the seafloor. They are among the most species-rich areas of deep-water marine ecosystems. Their structure provides areas for other species to rest, feed, spawn, and avoid predators. They may also provide protection for eggs and juveniles of various species. Sponges contribute significantly to the nitrogen, carbon and silicon cycles in the ocean. This results from their large filter-feeding capacity, a diet mainly composed of dissolved organic matter, and a silicified skeleton.

Before 2000, coral distributions were based on reports of accidental catches from fish harvesters. Since then, DFO scientists, academic colleagues, environmentalists, and fishermen have collaborated on deep-sea research surveys using trawls and remotely operated vehicles to improve our knowledge of coral and sponge distributions.

Status and trends

Sand dollar beds

Figure 17: Distribution of sand dollars in the Scotian Shelf bioregion from DFO multispecies trawl surveys (1999–2015) and scallop stock assessment surveys (1997, 2007). Sand dollars are particularly abundant in the Bay of Fundy, eastern Scotian Shelf, Georges Bank, Gulf of St. Lawrence, and the Grand Banks. (Reproduced with permission from Beazley et al. 2017). A map of the Scotian Shelf showing the distribution of sand dollars. Text above the map says “Distribution of sand dollars in areas of the Scotian Shelf”. The area on the map goes from the Gulf of St. Lawrence and southern shore of Newfoundland at the top to Georges Bank at the bottom left with an outline of the Scotian Shelf bioregion. A legend in the bottom left-hand corner has text at the top saying “Presence of sand dollars in Scotian Shelf bioregion”. Areas which have been surveyed are indicated by a blue shading, and the Scotian Shelf bioregion is shaded in orange. Red dots on the map indicate presence of sand dollars based on DFO scallop dredge survey records, and black dots indicate presence of sand dollars based on DFO multispecies trawl survey records. The Scotian Shelf bioregion extends to the right off the east coast of Nova Scotia. The area surveyed extends from the coast approximately half-way across the region. Black dots are spread across the shelf in the eastern portion of this surveyed area with a generally uniform distribution. Fewer black dots are located in the western portion of the area with a small cluster in the far bottom left corner. Another cluster occurs in the upper Bay of Fundy. A linear group of red dots is located along the eastern shore of the Bay of Fundy and part way around the western tip of Nova Scotia.

Figure 17: Distribution of sand dollars in the Scotian Shelf bioregion from DFO multispecies trawl surveys (1999–2015) and scallop stock assessment surveys (1997, 2007). Sand dollars are particularly abundant in the Bay of Fundy, eastern Scotian Shelf, Georges Bank, Gulf of St. Lawrence, and the Grand Banks. (Reproduced with permission from Beazley et al. 2017)

In eastern Canada, the common sand dollar (Echinarachnius parma) forms dense groups called beds that occur from shallow intertidal waters out to the offshore continental shelves (Figure 17). Contrary to their name, sand dollars are found in a range of sediment types, from coarse gravelly sand to fine silt. They feed on benthic diatoms (algae), organic and other small particles while burrowing using small tentacles.

Sand dollars are a key species in the Atlantic because they are “bioturbators” — they rapidly disturb and mix sediments as they feed and burrow. This provides more oxygen deeper in the sediment, which allows more organisms to live there. On the Scotian Shelf, sand dollars are significant contributors to disturbing sediments on the ocean floor (second only to storms). Sand dollars can occur in dense aggregations (as many as 180 per square metre on Sable Island Bank), some of which have been considered in the identification of ecologically and biologically significant areas (EBSAs).

Information on the distribution of sand dollars has been collected from multispecies trawl surveys, some scallop stock assessment surveys, and targeted research studies.

Status and trends

Fish and invertebrate communities

Marine fish and invertebrates within pelagic (open water), demersal (near-bottom), and benthic (bottom-dwelling) communities are part of a complex ecological network. These communities are closely connected to the physical, chemical and biological environment in which they live. Depending on what they eat, fish and invertebrates occupy different parts of the food web and play an important role in the transfer of energy and nutrients along food chains from producers like plants to consumers like humans. A change in the structure of one marine community can have major influences on the health of other communities.

Fish and invertebrates (crustaceans and shellfish) are an important source of food for Canadians and are one of Canada’s major food exports. Scientific information on the status and trends of fish and invertebrate communities are needed to make sustainable and responsible management decisions to maintain resource conservation while securing the future of our fisheries.

Fisheries target specific species and catches from these fisheries provide useful information for management, but fishery catches do not reflect all communities of the marine ecosystem. To compensate, scientific surveys are conducted by researchers to collect additional data and provide information on wider marine communities. Assessing the state of marine fish and invertebrate communities requires careful monitoring and scientific analysis.

STATUS & TRENDS – ATLANTIC BIOREGION

It’s complicated: seals and Atlantic cod

In the early 1990s, there was a widespread collapse of Atlantic cod stocks off the east coast of Canada. Suspected reasons for this collapse were varied: overfishing, unreported catches, declines in productivity, high natural mortality because of poor ocean conditions, and increased predation.

There are seven Atlantic cod stocks in Atlantic Canada (Figure 18). Some appear to be recovering slowly. Others remain at low levels or continue to decline even though there are strict management measures in place to limit fishing effort since then. At the same time, harp and grey seal populations have increased in abundance, reaching numbers not seen over the last 50 years (Figure 19). This has led to the suggestion that the lack of recovery of Atlantic cod and other demersal populations is due to “over-abundant” seal populations eating large amounts of fish.

Research has shown that factors affecting Atlantic cod recovery are complex. The role of seal predation, as well as other factors, differs between bioregions. Examples of these differences by regional cod stocks are outlined below.

Atlantic cod stocks off the northeast coast of Newfoundland (2J3KL) have increased in abundance between 2005 and 2016 despite a large harp seal population. However, they are nowhere near their historical levels or the numbers needed for conservation. A recent study showed that fishing and the limited availability of capelin account for the slow recovery of cod. Seal consumption was not found to be an important cause of either the decline or slow rate of recovery.

In the northern Gulf of St. Lawrence (4RS/3Pn), the cod stock also shows signs of recovery, but it is slow. Scientists studying the various potential causes—fishing, environmental conditions, and predation—point to very poor young cod survival as the main cause. A combination of overfishing, predation by harp seals, and cold water temperatures in the 1990s were the main factors for this poor survival.

In the southern Gulf (4T), large cod continue to decline and extremely high mortality among mature fish prevents the stock’s recovery. Under the current high rates of mortality, cod could become extinct in this area within approximately 40 years. Here, scientists consider that grey seal predation is important, accounting for up to 50 percent of cod mortality, although other factors might also come into play.

Figure 18: Location of cod stocks in Atlantic Canada. Of the seven Atlantic cod stocks in the Canadian Atlantic, some appear to be recovering slowly, whereas others remain at low levels or continue to decline. The importance of overfishing, environmental conditions, capelin availability, and predation by seals is different between bioregions. A map of the Canadian Atlantic highlighting the location of Atlantic cod stocks. Text above the map says “Location of cod stocks in Atlantic Canada”. The map shows eastern Canada from Quebec and Labrador in the north to Nova Scotia and the eastern United States in the south extending and showing the marine areas to the east. On the left-hand edge of the map, tick marks indicate the 40°N, 50°N, and 60°N latitude lines and ticks on the bottom edge indicate the 70°W, 60°W, and 50°W longitude lines. Boundaries of the Northwest Atlantic Fisheries Organization (NAFO) sub-divisions are also shown in the waters off the Atlantic coast as polygons bordered by white dashed lines. Each NAFO area has a number and letter to indicate their name. Seven coloured ovals with numbered and lettered names represent each stock on the map. The ovals are located across different marine areas of the Atlantic coast. Cod stock 4X is green and located off the southwestern tip of Nova Scotia, 4VSW is teal and is located southeast of Nova Scotia, 4T is yellow and is located in the southern Gulf of St. Lawrence, 4Rs is orange and is located in the northern Gulf of St. Lawrence, 3PS is blue and is located southwest of Newfoundland and Labrador, 3NO is purple and is located southeast of Newfoundland and Labrador, 2J3KL is red and is located northeast of Newfoundland and Labrador.

Figure 18: Location of cod stocks in Atlantic Canada. Of the seven Atlantic cod stocks in the Canadian Atlantic, some appear to be recovering slowly, whereas others remain at low levels or continue to decline. The importance of overfishing, environmental conditions, capelin availability, and predation by seals is different between bioregions.

Figure 19: The abundance of harp seals and grey seals in Atlantic Canada. They have been increasing in abundance to levels not seen in 50 years. A line graph illustrates the population of grey and harp seals in Atlantic Canada. Text above the graph says “Abundance of harp and grey seals”. Two vertical axes are found on the graph, each representing one seal species. The axis at left shows numbers from 0 to 10,000 in increments of 1000 with text that reads “Harp seals (thousands). The axis at right shows numbers from 0 to 700 in increments of 100 with text that reads “Grey seals (thousands). The horizontal axis shows years between 1960-2010 in 10 year increments. A legend appears in the top left-hand corner of the graph. The harp seal abundance is represented by an orange line which increases over time from between 1000 to 2000 thousand in the 1970s to the 2000s it reachs almost 8000 thousand. A green line represents grey seal abundance which also increases over time although it is lower than the orange line. It starts near zero in the 1960s and increases to over 600 thousand. Each line is surrounded by a shaded area which represents the confidence in the abundance value.

Figure 19: The abundance of harp seals and grey seals in Atlantic Canada. They have been increasing in abundance to levels not seen in 50 years.

Gulf of St. Lawrence

There are two main scientific research surveys carried out annually in different areas of the Gulf of St. Lawrence bioregion. The bioregion is therefore assessed as two sub-regions: the northern Gulf (4R, 4S) and the southern Gulf (4T). An annual September survey was started in the southern Gulf In in 1971. Then in 1990, an August survey was started for the Estuary and northern Gulf. These surveys use bottom trawls to gather information about the species present and their abundance.

Bottom trawls are not ideal for assessing pelagic fish species, since they live in open water. Therefore targeted surveys are carried out for some pelagic stocks such as Atlantic herring. For other species that do not have targeted surveys, the landings of commercial fisheries can be used to better understand the state of those stocks. When using this type of data, scientists have to keep in mind that the amount of effort put into fishing can influence the landings. As a result, they must be cautious when comparing with research survey data.

Status and trends (Gulf of St. Lawrence)

Figure 20: Survey biomass for total demersal fish and individual species in the southern Gulf of St. Lawrence. A bar and line graph illustrates the survey biomass for total demersal fish as well as individual species in the southern Gulf of St. Lawrence. Text above the graph says “Southern Gulf of St. Lawrence Survey – Demersal Fish”. The vertical axis on the left shows the survey biomass in units of kilograms per tow from 0 to 400 in increments of 100. The bottom horizontal axis shows the years between 1970 and 2020 in 10 year increments. The biomass for total demersal fish in the survey is represented by grey vertical bars. There is an increase in biomass between 1970 and the early 1980s peaking just over 400 kilograms per tow. It decreases in the early 1990s and it remains low until the last year of data in 2016 when it is less than 100 kilograms per tow. Five demersal fish species are represented by different coloured lines on the same graph. A legend appears on the right. A green data line shows the survey biomass of American plaice. An orange data line represents the survey biomass of Atlantic halibut. A light blue data line represents the survey biomass of Atlantic cod. A dark green data line represents the survey biomass of Greenland halibut. A dark red data line represents the survey biomass of redfish (all species). In the early 1970s, the survey biomass for each species is below 100 kilograms per tow. American plaice, Atlantic cod and redfish have the highest biomasses fluctuating around 50 kilograms per tow, while Greenland halibut and Atlantic halibut have the lowest biomasses. American plaice increases in the 1970s to 1980s to just over 100 kilograms per tow and then decreases again in the late 1970s to 1980s and then remains low. Atlantic cod also increases in the late 1970s to the 1980s fluctuating around 200 kilograms per tow which is the higher than any other species on the graph. There is a large decline in the early 1990s and then it then remains low. Redfish survey biomass fluctuates around approximately 50 kilograms per tow throughout the 1970s to early 1990s when it decreases. There is a modest increase in recent years. Atlantic halibut has a low biomass compared with the other species across the graph with a modest increase in the 2010s. Greenland halibut also has low survey biomass across the graph compared to the other species with a modest increases during the 2000s and early 2010s. A small, light blue outline drawing of an Atlantic cod is placed just above the vertical bars and centred over the year 2000. Below the drawing there is text which states “Demersal fish including Atlantic cod collapsed and remain at historic lows”.

Figure 20: Survey biomass for total demersal fish and individual species in the southern Gulf of St. Lawrence.

Figure 21: Survey biomass for total demersal fish and individual species in the northern Gulf of St. Lawrence. A bar and line graph illustrates the survey biomass for total demersal fish as well as individual species in the northern Gulf of St. Lawrence. Text above the graph says “Northern Gulf of St. Lawrence Survey – Demersal Fish”. The vertical axis on the left shows the survey biomass in units of kilograms per tow from 0 to 600 in increments of 100. The bottom horizontal axis shows the years between 1990 and 2020 in 10 year increments. The biomass for total demersal fish in the survey is represented by grey vertical bars. The survey biomass is approximately 200 kilograms per tow in 1990 and decreases through the early 1990s remaining below 100 kilograms per tow across most of the graph. It begins to rise in the 2010s peaking above 500 kilograms per tow in 2017 which is the last year of data on the graph. Five demersal fish species are represented by different coloured lines on the same graph. A legend appears on the left. A dark red data line shows the survey biomass of Acadian redfish. An orange data line shows the survey biomass of Atlantic halibut. A light blue data line shows the survey biomass of Atlantic cod. A light red data line shows the survey biomass of Atlantic redfish. A dark green data line shows the survey biomass of Greenland halibut. The survey biomasses for individual species all remain at or below 100 kilograms per tow across the graph until the mid-2010s. Acadian redfish, Atlantic redfish, and Atlantic cod generally have the highest  survey biomasses, but they each decrease during the early 1990s and then remain low until the 2000s. Atlantic redfish begins to increase rapidly in the 2010s, peaking at approximately 500 kilograms per tow in 2017. Atlantic cod increases slowly in the 2000s but decreases again in 2017. Greenland halibut and Atlantic halibut have lower survey biomasses compared to the other three species. Greenland halibut increases in the 1990s, but declines in the recent years while Atlantic halibut increases after 2010. Above the vertical bars to the left-hand side of the graph, a line of text says “Demersal fish including Atlantic cod collapsed”. An arrow under the text points down towards 1991. A small, light blue outline drawing of a redfish is placed just above the vertical bars to the right-hand side. Below the drawing there is text which states “redfish increasing” and an arrow points downward to the light red line. Another line of text on the far right-hand side of the graph says “Atlantic cod decreased in 2017”. An arrow points from the text to the light blue line in 2017.

Figure 21: Survey biomass for total demersal fish and individual species in the northern Gulf of St. Lawrence.

Figure 22: Survey biomass for total pelagic fish and Atlantic herring in the southern Gulf of St. Lawrence. A bar and line graph illustrates the survey biomass for total pelagic fish as well as Atlantic herring in the southern Gulf of St. Lawrence. Text above the graph says “Southern Gulf of St. Lawrence Pelagic Fish Survey”. The vertical axis on the left shows the survey biomass in units of kilograms per tow from 0 to 150 in increments of 50. The bottom horizontal axis shows the years between 1970 and 2020 in 10 year increments. The survey biomass for total pelagic fish in the survey is represented by grey vertical bars. The total pelagic fish survey biomass is low throughout the 1970s, but increases rapidly in the 1980s. It then generally fluctuates between approximately 25 and 50 kilograms per tow with two peaks above 100 kilograms per tow in the late 2000s and early 2010s. It decreases in 2016 which is the last year of data on the graph. The survey biomass of Atlantic herring is represented by a green line on the same graph. A legend appears on the left. The Atlantic herring survey biomass generally reflects that of the total pelagic fish survey biomass. It is low during the 1970s and then increases in the 1980s and remains mostly between 25 and 50 kilograms per tow with two peaks above 100 kilograms per town in the late 2000s to early 2010s. Then in the 2010s it decreases. A small, light blue outline drawing of an Atlantic herring is placed above the vertical bars to the left-hand side of the graph. Below the drawing there is text which states “Atlantic herring increased in the 1980s”. An arrow points down to the mid-1980s period. Another line of text on the right-hand side of the graph says “Recently declining”. An arrow points from the text to the mid-2010s period.

Figure 22: Survey biomass for total pelagic fish and Atlantic herring in the southern Gulf of St. Lawrence.

Figure 23: Survey biomass for total pelagic fish and individual species in the northern Gulf of St. Lawrence. A bar and line graph illustrates the survey biomass for total pelagic fish as well as individual species in the northern Gulf of St. Lawrence. Text above the graph says “Northern Gulf of St. Lawrence Pelagic Fish Surveys”.The vertical axis on the left shows the survey biomass in units of kilograms per tow from 0 to 1000 in increments of 250. The bottom horizontal axis shows the years between 1970 and 2020 in 10 year increments. The biomass for total pelagic fish in the survey is represented by grey vertical bars. The data extends from 1968 to 2017. The total survey biomass fluctuates between approximately 400 to 500 thousand tonnes in the 1970s and 1980s, with a peak in the early 1980s of near 600 thousand tonnes. It increases rapidly in the mid-1980s with a peak of approximately 850 thousand tonnes and then fluctuating between 600 to 700 thousand tonnes. It decreases through the 1990s to almost 100 thousand tonnes then increases in the early 2000s to approximately 250 thousand tonnes. It decreases again over the 2010s to near 100 thousand tonnes. The survey biomass of individual pelagic species is represented by coloured lines on the same graph. A legend appears on the right. A dark blue data line shows the survey biomass of Atlantic herring for fall in the 4R NAFO zone. A light blue data line shows the survey biomass of Atlantic herring for spring in the 4R NAFO zone. A yellow data line shows the survey biomass of Atlantic mackerel in NAFO Subareas 3 and 4. The survey biomass of Atlantic mackerel is higher than the other species on the graph and is similar to the overall trend for total survey biomass of pelagic fish. In the early 1970s it fluctuates around 250 thousand tonnes, increasing in the late 1970s to a peak near 500 thousand tonnes. It then increases again in the late-1980s peaking below 700 thousand tonnes. It decreases in the 1990s below 100 thousand tonnes. There is a modest increase in the early 2000s but then it decreases until the 2010s where it remains at a low level. The survey biomass of Atlantic herring in 4R for spring and fall surveys both remain below the Atlantic mackerel biomass until the mid-2000s. The 4R fall Atlantic herring biomass is near 250 thousand tonnes in the late 1960s, but decreases and remains low until the mid-2000s when it increases again to near 250 thousand tonnes. In the 2010s it begins to decrease again. The 4R spring Atlantic herring biomass has a slight increase in the mid-1970s, but is generally low throughout the time period of the graph and decreases in the 2000s and 2010s. A small, light blue outline drawing of an Atlantic mackerel is placed above the vertical bars to the right-hand side of the graph. Below the drawing there is text which states “Atlantic mackerel declined in the 1990s and collapsed in the 2010s”. An arrow points down to the 1990s period and another to the 2010 period. Another line of text farther on the right-hand side of the graph says “Atlantic herring stocks declining”. An arrow points from the text to the 2010s period.

Figure 23: Survey biomass for total pelagic fish and individual species in the northern Gulf of St. Lawrence.

Figure 24: Survey biomass for benthic invertebrates, American lobster and snow crab in the southern Gulf of St. Lawrence. A bar and line graph illustrates the survey biomass for benthic invertebrates as well as individual species in the southern Gulf of St. Lawrence. Text above the graph says “Southern Gulf of St. Lawrence Survey - Invertebrates”. The vertical axis on the left shows the survey biomass in units of kilograms per tow from 0 to 150 in increments of 50. The bottom horizontal axis shows the years between 1990 and 2020 in 10 year increments. The biomass for total pelagic fish in the survey is represented by grey vertical bars. The data extends from 1988 to 2016. The total survey biomass fluctuates around 25 kilograms per tow with peaks of near 50 kilograms per tow in 1990 and 2000. Another peak just above 100 kilograms per tow occurs in 2007. The survey biomass of individual species is represented by coloured lines on the same graph. A legend appears on the left. A red data line shows the survey biomass for American lobster. A light red data line shows the survey biomass for snow crab. Both snow crab and American lobster biomasses are fairly flat across the time period of the graph and fluctuate generally below 10 kilograms per tow. Snow crab biomass is higher than American lobster until the late 2000s when American lobster biomass increases. A small, light blue outline drawing of an American lobster is placed above the vertical bars to the right-hand side of the graph. Below the drawing there is text which states “American lobster increasing”. An arrow points from the text to the mid-2010s period.

Figure 24: Survey biomass for benthic invertebrates, American lobster and snow crab in the southern Gulf of St. Lawrence.

Figure 25: Commercial fishery landings for benthic invertebrates along with individual species in the northern Gulf of St. Lawrence. New fisheries include green sea urchin, sea cucumber and Arctic surf clam. Other traditional species are Atlantic rock crab, Hyas crab, giant scallop, whelk, common softshell clam, Atlantic jacknife clam and Atlantic surfclam. A bar and line graph illustrates the commercial fishery landings for benthic invertebrates as well as individual species in the northern Gulf of St. Lawrence. Text above the graph says “Northern Gulf of St. Lawrence Invertebrate Commercial Fishery Landings”.The vertical axis on the left shows the survey biomass in units of thousands of tonnes from 0 to 25 in increments of 5. The bottom horizontal axis shows the years between 1970 and 2020 in 10 year increments. The commercial fishery landings for benthic invertebrates is represented by light blue vertical bars. The data extends from 1970 to 2016. The commercial landings are less than 5 thousand tonnes in the 1970s and early 1980s. In 1983 it jumps up above 5 thousand tonnes and continually increases with some fluctuations until it is near 20 thousand tonnes by the mid-2010s. The commercial fishery landings of individual species are represented by coloured lines on the same graph. A legend appears on the left. A red data line shows the commercial fishery landings of American lobster. A pink data line shows the commercial fishery landings of snow crab. A light blue dashed data line shows the commercial fishery landings for new fisheries. A green dashed data line shows the commercial fishery landings for other traditional species. The trend for American lobster landings starts below 5 thousand tonnes and gradually increases over the period of the graph ending near 5 thousand tonnes by the mid-2010s. The landings for other traditional species and new fisheries are lower than American lobster. The other traditional species landings begin to gradually increase in the 1980s and 1990s until they near 5 thousand tonnes and then decrease to near 3 thousand tonnes in the mid-2010s. The new fisheries landings begin to increase in the 1990s and are near 2 to 3 thousand tonnes by the mid-2010s. The snow crab landings begin in 1983 below 5 thousand tonnes. They increase in the 1990s and near 10 thousand tonnes by the early 2000s. They drop and then gradually increase in the mid-late 2000s and 2010s again nearing 10 thousand tonnes. A small, light blue outline drawing of a snow crab is placed above the vertical bars to the left-hand side of the graph. Below the drawing there is text which states “Start of snow crab fishery”. An arrow points from the text to the start of the pink data line in 1983. Another line of text above the vertical bars on the right-hand side of the graph says “Warming favours American lobster”. An arrow points from the text to the red data line in the 2010s.

Figure 25: Commercial fishery landings for benthic invertebrates along with individual species in the northern Gulf of St. Lawrence. New fisheries include green sea urchin, sea cucumber and Arctic surf clam. Other traditional species are Atlantic rock crab, Hyas crab, giant scallop, whelk, common softshell clam, Atlantic jacknife clam and Atlantic surfclam.

Figure 26: Survey biomass for northern shrimp in the northern Gulf of St. Lawrence. A bar graph illustrates the survey biomass for northern shrimp in the northern Gulf of St. Lawrence. Text above the graph says “Northern Gulf of St. Lawrence Northern Shrimp Survey”. The vertical axis on the left shows the survey biomass in units of kilograms per tow from 0 to 75 in increments of 25. The bottom horizontal axis shows the years between 1990 and 2020 in 10 year increments. The biomass of northern shrimp is represented by yellow vertical bars. A legend appears on the right. The biomass increases in the 1990s and peaks in 2003 between 50 and 75 kilograms per tow. After 2005 it declines until the last year of data in 2017. A small, light blue outline-drawing of a shrimp is placed on the graph above the vertical bars to the left hand-side. Below the drawing there is text which states “Benthic invertebrates increased after the demersal fish collapse”.

Figure 26: Survey biomass for northern shrimp in the northern Gulf of St. Lawrence.

Scotian Shelf

When describing fish and invertebrate communities, the Scotian Shelf is divided into two broad sub-regions: the eastern Scotian Shelf (4W, 4V) and the western Scotian Shelf and the Bay of Fundy (4X). Research vessel surveys use bottom trawls to assess the fish and invertebrate communities in this bioregion, although commercial fishery landings are also used to add to the available data.

Status and trends (Scotian Shelf)

Figure 27: 4VW (eastern Scotian Shelf) survey biomass for total demersal fish and individual species. A bar and line graph illustrates the survey biomass for total demersal fish as well as individual species for the 4VW NAFO zone of the eastern Scotian Shelf. Text above the graph says “4VW Scotian Shelf Survey – Demersal Fish”. The vertical axis on the left shows the survey biomass in units of thousands of tonnes from 0 to 800 in increments of 200. The bottom horizontal axis shows the years between 1970 and 2020 in 10 year increments. The biomass for total demersal fish in the 4VW survey is represented by grey vertical bars. The total survey biomass increases from approximately 400 thousand tonnes in 1970 to approximately 700 thousand tonnes in 1979. There is a large decline in the late 1980s and early 1990s to approximately 200 thousand tonnes. After that it is low with some fluctuation. The last year of data is 2017. Six demersal fish species are represented by different coloured lines on the same graph. A legend appears on the right. A dark blue data line illustrates the survey biomass trend for Atlantic cod. A black data line illustrates the survey biomass trend for spiny dogfish. A yellow data line illustrates the survey biomass trend for haddock. An orange data line illustrates the survey biomass trend for Atlantic halibut. A red data line illustrates the survey biomass trend for redfish (all species). A light blue data line illustrates the survey biomass trend for silver hake. Atlantic cod biomass peaks at approximately 200 thousand tonnes in the early 1980s. It then decreases in the late 1980s and early 1990s and remains low to 2017. Redfish biomass is higher than other species in the 1970s with fluctuations. It peaks at near 400 thousand tonnes in the late 1970s, but then decreases in the 1980s to near 100 thousand tonnes and lower again in the 1990s. In the late 2000s and early 2010s it rises and then declines again. Haddock biomass increases to near 100 thousand tonnes in the late 1970s and decreases in the early 1990s. It remains at that level with some fluctuations until 2017. Silver hake increases during the 1980s when it is between 50 and 100 thousand tonnes, but then declines in the late 1980s and early 1990s. It increases modestly in the 2010s. Spiny dogfish and Atlantic halibut have very low biomass compared to the other species on the graph. Spiny dogfish shows no trend and Atlantic halibut biomass increases slightly in the 2010s. A small, light blue outline-drawing of a haddock is placed on the graph overlapping the vertical bars on the top to the left hand-side. Below the drawing there is text which states “Demersal fish collapsed in the late 1980s – early 1990s”. Another line of text lies to the right hand-side of the graph just overlapping the top of the vertical bars which says “Atlantic cod remains low”.

Figure 27: 4VW (eastern Scotian Shelf) survey biomass for total demersal fish and individual species.

Figure 28: 4X (western Scotian Shelf and Bay of Fundy) survey biomass for total demersal fish and individual species. A bar and line graph illustrates the survey biomass for total demersal fish as well as individual species for the 4X NAFO zone of the eastern Scotian Shelf. Text above the graph says “4X Scotian Shelf Survey – Demersal Fish”. The vertical axis on the left shows the survey biomass in units of thousands of tonnes from 0 to 800 in increments of 200. The bottom horizontal axis shows the years between 1970 and 2020 in 10 year increments. The biomass for total demersal fish in the 4VW survey is represented by grey vertical bars. The total survey biomass fluctuates between approximately 200 thousand tonnes and 600 thousand tonnes over the timespan of 1970 to 2017 with no long-term trend. Six demersal fish species are represented by different coloured lines on the same graph. A legend appears on the left. A dark blue data line illustrates the survey biomass trend for Atlantic cod. A black data line illustrates the survey biomass trend for spiny dogfish. A yellow data line illustrates the survey biomass trend for haddock. An orange data line illustrates the survey biomass trend for Atlantic halibut. A red data line illustrates the survey biomass trend for redfish. A light blue data line illustrates the survey biomass trend for silver hake. Atlantic cod biomass between 1970 and 2010 is less than 50 thousand tonnes with small fluctuations. In the mid-2000s the biomass decreases and remains very low. There is a peak in redfish biomass in the early 1970s, and then it fluctuates around 100 thousand tonnes until the mid-2000s when it is generally higher with peaks of approximately 300 thousand tonnes. Spiny dogfish biomass fluctuates, but after the 1980s is generally higher with peaks between 200 and 400 thousand tonnes. Haddock is generally below 100 thousand tonnes with small fluctuations and no trend until it increases in the mid-2010s. Atlantic halibut has a low biomass compared to other species on the graph, but increases in recent years. Silver hake biomass is low compared to the other species with small fluctuations. A small, light blue outline-drawing of a redfish is placed on the graph above the vertical bars to the right-hand side. Below the drawing there is text which states “redfish populations at historic highs”. An arrow points from the text to the red line in the mid-2010s.

Figure 28: 4X (western Scotian Shelf and Bay of Fundy) survey biomass for total demersal fish and individual species.

Figure 29: Scotian Shelf commercial landings for pelagic fish. A bar graph illustrates the commercial landings for pelagic fish on the Scotian Shelf. Text above the graph says “Scotian Shelf Pelagic Fish Commercial Landings”. The vertical axis on the left shows the commercial landings in units of thousands of tonnes from 0 to 300 in increments of 100. The bottom horizontal axis shows the years between 1970 and 2020 in 10 year increments. The commercial landings are represented by light blue vertical bars. The landings begin between 200 and 250 thousand tonnes in the early 1970s. There is a decline in the late 1980s to early 1990s and the decline continues to the last year of data in 2015. A small, light blue outline-drawing of an Atlantic herring is placed on the graph above the vertical bars to the right hand-side. Below the drawing there is text which states “Landings of Atlantic herring and other pelagic fish have been decreasing”.

Figure 29: Scotian Shelf commercial landings for pelagic fish.

Figure 30: Scotian Shelf commercial landings for benthic invertebrate species and survey biomass for individual benthic invertebrate species. Commercial landings show a long-term increasing trend. Data collection by research survey began in 1999. A bar graph illustrates commercial landings for benthic invertebrates combined with line graphs illustrating the survey biomass for individual invertebrate species on the Scotian Shelf. Text above the graph says “Scotian Shelf Invertebrate Commercial Landings and Survey Biomass of Species”. The vertical axis on the left shows the biomass in units of thousands of tonnes from 0 to 120 in increments of 30. The bottom horizontal axis shows the years between 1970 and 2020 in 10 year increments. The commercial landings are represented by light blue vertical bars which increase steadily with some fluctuations from approximately 15 thousand tonnes in the early 1970s to almost 120 thousand tonnes in the last year of data in 2015. The survey biomass of three invertebrates species are represented by different coloured lines on the same graph. The survey data starts in 1999 and ends in 2017. A legend appears on the left. A red data line illustrates the survey biomass trend for American lobster. A yellow data line illustrates the survey biomass trend for northern shrimp. A pink data line illustrates the survey biomass trend for snow crab. Northern shrimp biomass is higher than the other species on the graph. It fluctuates between approximately 15 thousand tonnes to 40 thousand tonnes, declining in recent years. The American lobster biomass fluctuates around 10 thousand tonnes until 2010 and then increases rapidly to approximately 30 thousand tonnes by the mid-2010s. The trend of the snow crab biomass is below 10 thousand tonnes with small fluctuations, and is lower in the last years of data. A line of text is placed to the left-hand side of the graph just above the vertical bars. It says “Benthic invertebrates increased as demersal fish decreased in the early 1990s”. A small, light blue outline-drawing of an American lobster is placed on the graph above the vertical bars to the right-hand side. Below the drawing there is text which states “Warming waters favour American lobster but northern shrimp and snow crab are declining”. An arrow points down to the red line in the mid-2010s.

Figure 30: Scotian Shelf commercial landings for benthic invertebrate species and survey biomass for individual benthic invertebrate species. Commercial landings show a long-term increasing trend. Data collection by research survey began in 1999.

Novel warm-water species

Surveys to monitor environmental conditions and fish populations off the Atlantic coast in recent years have yielded some surprises: an increasing number of warm-water fish species, some of which had been regularly caught further south on Georges Bank are now being more frequently observed on the Scotian Shelf.

The average bottom temperature of the Scotian Shelf and Bay of Fundy waters is 6.8℃ during the summer. This varies from year to year, with the warmest temperatures experienced in the last six years. Bottom trawl catches from the annual summer survey have yielded different species depending on the temperature (Figure 31). Some species, like the barndoor skate, are now regularly caught.

During the past five years, however, the number of exotic warm-water species captured has increased. So has the frequency at which they are captured. Catches of American John Dory, armored sea robin, spotted tinselfish, and deep-bodied boarfish are much more common (Figure 32). Some, like the blackbelly rosefish appear to be here to stay. They are captured every year on the Scotian Shelf and their distribution range is expanding as the ocean bottom warms.

Figure 31: Distribution by decade of captures of warm-water fish species overlain on the average temperature for each time period. Black dots represent a fishing set in which at least one warm-water fish species was present. Recently, the number and frequency of warm-water species captures has increased. A caption at the top a line of text says “Warmer Water”. Another line of text under that says “As the water warms, exotic warm-water species are seen more often in the region”. Under the text, five vertically stacked maps from 1970 to 2017 show changes in water temperature and warm-water species captures over time. The maps represent 1970-1979, 1980-1989, 1990-1999, 2000-2009, and 2010-2017 respectively from top to bottom. Each map shows the same area of the east coast of Canada centred on New Brunswick and Nova Scotia and showing the Scotian Shelf from the Gulf of St. Lawrence in the north to Georges Bank in the southwest. The Scotian Shelf area of each map is shaded with colours representing the average temperature for each time period. A legend to the right of the maps shows the range of temperatures and the colours used to represent them on the map. There are 12 colours each representing a span of temperatures. A dark blue at the top of the legend represents the range of 1.4-2.8°C and at the bottom a red represents temperatures >10°C. Each colour represents a range of 0.4 to 1.4°C. At the bottom of the legend there is a black dot with text next to it that says “Exotic warm water species captured in this location”. On the top map, the colouring of the shelf shows an area of darker blue on the eastern end of Scotian Shelf. The colour then transitions to lighter blues and then yellow and orange in the middle of the Scotian Shelf. There is then a small area of blue further down and then more yellow in the shaded area which bends around the western end of Nova Scotia into the Bay of Fundy. A few black dots are scattered towards the middle and bottom edges of the Scotian Shelf. Another few dots are located at the top of the Bay of Fundy. This general pattern of colour shading is seen on each map but the yellow and orange areas get darker and wider moving down the stack indicating that the temperature is increasing over time especially in the middle of the Shelf and near the bottom edge. The number of black dots also increases and they are generally located in the middle to western edges of the Scotian Shelf and upper Bay of Fundy with a few scattered in other areas.

Figure 31: Distribution by decade of captures of warm-water fish species overlain on the average temperature for each time period. Black dots represent a fishing set in which at least one warm-water fish species was present. Recently, the number and frequency of warm-water species captures has increased.

Figure 32: Varieties of “exotic” fishes captured on the Scotian Shelf: (A) armored searobin (Peristedion miniatum), (B) spotfin dragonet (Foetorepus agassizii), (C) glasseye snapper (Heteropriacanthus cruentatus), (D) deep-bodied boarfish (Antigonia capros), (E) American John Dory (Zenopsis ocellata) (partial). (Photo: W. Joyce, DFO). Photograph of five rare fish species of various sizes caught off the Scotian Shelf with letters A-E accompanying each species.

Figure 32: Varieties of “exotic” fishes captured on the Scotian Shelf: (A) armored searobin (Peristedion miniatum), (B) spotfin dragonet (Foetorepus agassizii), (C) glasseye snapper (Heteropriacanthus cruentatus), (D) deep-bodied boarfish (Antigonia capros), (E) American John Dory (Zenopsis ocellata) (partial). (Photo: W. Joyce, DFO)

Newfoundland and Labrador Shelves

The Newfoundland and Labrador Shelves bioregion can be considered as four large functional ecosystems, three of which have long-term data available: the Newfoundland Shelf (2J3K), the Grand Bank (3LNO), and southern Newfoundland (3Ps). Fish and invertebrate stocks are monitored by research trawl surveys which are carried out in spring and fall of each year. The spring survey covers the area from southern Newfoundland (3P) to the Grand Bank (3LNO). The fall survey covers the Newfoundland and Labrador Shelves from 2H to 3NO. The type of trawl gear used in the surveys changed in fall of 1995, so the data are adjusted to make comparisons possible.

As bottom trawls do not give a complete picture for pelagic fish, targeted surveys are sometimes carried out. For example, capelin in 3L has been assessed using acoustic survey methods.

Status and trends (Newfoundland and Labrador Shelves)

Figure 33: Fall survey biomass of demersal fish species in 2J3K on the Newfoundland and Labrador Shelves along with individual demersal species biomass. A bar and line graph illustrates the fall survey biomass for demersal fish as well as individual species for the 2J3K NAFO zone of the Newfoundland and Labrador Shelves. Text above the graph says “Newfoundland and Labrador Shelves 2J3K Fall Survey – Demersal Fish”. The vertical axis on the left shows the scaled survey biomass index in units of thousands of tonnes from 0 to 6000 in increments of 1000. The bottom horizontal axis shows the years between 1980 and 2020 in 10 year increments. The biomass for total demersal fish is represented by grey vertical bars. The total survey biomass is between 3000 and 5500 thousand tonnes in the early 1980s and then there is a large decline to approximately 250 thousand tonnes by 1992. It remains low in the 1990s and 2000s, and then there is a modest increase in the mid-2000s to near 1000 thousand tonnes. The fall survey biomass for three demersal fish species is represented by different coloured lines on the same graph. A legend appears on the right. A yellow data line illustrates the survey biomass trend for American plaice. A light blue data line illustrates the survey biomass trend for American cod. A dark green data line illustrates the survey biomass trend for Greenland halibut. Atlantic cod biomass is over 1000 thousand tonnes in the 1980s, but then There is a large decline in the late 1980s and early 1990s with the biomass approaching the bottom of the graph. There is a modest increase starting in the mid-2000s bringing the biomass towards 300-400 thousand tonnes. American plaice and Greenland halibut biomasses are lower than Atlantic cod in the 1980s. American plaice is near 200 to 300 thousand tonnes but decreases in the late 1980s to early 1990s to less than 100 thousand tonnes. It remains low until the mid-2000s when has a modest increase. Greenland halibut biomass is generally around 200-300 thousand tonnes with a decline in the late 1980s and early 1990s to below 100 thousand tonnes. It increases again in the mid-1990s and then it stays 100 to 200 thousand tonnes. A small, light blue outline-drawing of an Atlantic cod is placed on the graph above the vertical bars to the left-hand side. Below the drawing there is text which states “Collapse of northern cod stock”. An arrow points from the text to the vertical bars for the early 1990s time period. Another line of text is placed on the graph to the right-hand side above the vertical bars which states “Atlantic cod remains at historically low levels”.

Figure 33: Fall survey biomass of demersal fish species in 2J3K on the Newfoundland and Labrador Shelves along with individual demersal species biomass.

Figure 34: Spring survey biomass of demersal fish species in 3LNO on the Newfoundland and Labrador Shelves along with individual demersal species biomass. A bar and line graph illustrates the spring survey biomass for demersal fish as well as individual species for the 3LNO NAFO zone of the Newfoundland and Labrador Shelves. Text above the graph says “Newfoundland and Labrador Shelves 3LNO Spring Survey – Demersal Fish”. The vertical axis on the left shows the scaled survey biomass index in units of thousands of tonnes from 0 to 4000 in increments of 1000. The bottom horizontal axis shows the years between 1985 and 2020 in 10 year increments. The biomass for total demersal fish in the spring 3LNO survey is represented by grey vertical bars. The data extends from 1985 to 2016, but there is no data for 2015. The total survey biomass fluctuates between approximately 3000 and 5500 thousand tonnes in the early 1980s and then declines to approximately 250 thousand tonnes by 1992. It remains below approximately 500 thousand tonnes until the mid-2000s when it starts to increase to 2010 and reaches approximately 1000 thousand tonnes. The fall survey biomass for three demersal fish species is represented by different coloured lines on the same graph. A yellow data line illustrates the survey biomass trend for American plaice. A light blue data line illustrates the survey biomass trend for American cod. A dark green data line illustrates the survey biomass trend for Greenland halibut. Atlantic cod biomass is the highest of the species in the 1980s ranging between 1000 and 2000 thousand tonnes, but it decreases rapidly less than 100 thousand tonnes in the early 1990s and remains low. The biomass of American plaice is near 1000 thousand tonnes in the 1980s, but decreases rapidly in the late 1980s and early 1990s. It then remains generally between 100-200 thousand tonnes to 2016. Greenland halibut has the lowest biomass of the three species and is less than 50 thousand tonnes with small fluctuations from the 1980s to 2016. A small, light blue outline-drawing of an Atlantic cod is placed on the graph above the vertical bars to the left-hand side. Below the drawing there is text which states “Collapse of northern cod stock” and an arrow points to the vertical bars for the early 1990s time period. Another line of text is placed on the graph to the right-hand side overlapping the vertical bars which states “Atlantic cod remains at historically low levels”.

Figure 34: Spring survey biomass of demersal fish species in 3LNO on the Newfoundland and Labrador Shelves along with individual demersal species biomass.

Figure 35: Capelin biomass from the spring acoustic survey in 3L on the Newfoundland and Labrador Shelves. A bar graph illustrates the spring acoustic survey biomass for capelin in NAFO Division 3L on the Newfoundland and Labrador Shelves. Text above the graph says “Newfoundland and Labrador Shelves Capelin (3L) Acoustic Survey”. The vertical axis on the left shows the acoustic survey biomass in units of thousands of tonnes from 0 to 6000 in increments of 1000. The bottom horizontal axis shows the years between 1980 and 2020 in 10 year increments. A legend appears on the right. The biomass of capelin is represented by red vertical bars and there is data between 1981 and 2017. Between 1985 and 1990 the biomass fluctuates between approximately 2500 and 4500 thousand tonnes, peaking near 6000 thousand tonnes in 1990. In 1991 the biomass decreases drastically, and remains very low until the mid-2000s when there is a modest increase. It peaks in the early-2010s near 1000 thousand tonnes and decreases again in the last few years. A small, light blue outline-drawing of a capelin is placed on the graph to the right of the vertical bars at 1990. Below the drawing there is text which states “capelin collapsed in 1991”. An arrow points from the drawing to 1991. Another line of text lies above the vertical bars to the right-hand side of the graph with arrows pointing to the left and right. The text says “Little to no recovery”.

Figure 35: Capelin biomass from the spring acoustic survey in 3L on the Newfoundland and Labrador Shelves.

Figure 36: The total fall survey biomass of benthic invertebrate species in 2J3K on the Newfoundland and Labrador Shelves along with individual invertebrate species survey biomass. A bar and line graph illustrates the fall survey biomass for benthic invertebrates (commercial species) as well as individual species for the 2J3K NAFO zones of the Newfoundland and Labrador Shelves. Text above the graph says “Newfoundland and Labrador Shelves 2J3K Fall Survey – Commercial Invertebrates Species”. The vertical axis on the left shows the scaled survey biomass index in units of thousands of tonnes from 0 to 1000 in increments of 250. The bottom horizontal axis shows the years between 1995 and 2020 in 5 year increments. The biomass for commercial invertebrates species is represented by grey vertical bars. The total survey biomass is at high levels throughout the late 1990s and 2000s. It peaks below 1000 thousand tonnes in 2006 and then declines to below 250 thousand tonnes by the last year of data in 2016. The fall survey biomass for two benthic invertebrates species is represented by different coloured lines on the same graph. A legend appears on the right. A yellow data line illustrates the survey biomass trend for northern shrimp. A red data line illustrates the survey biomass trend for snow crab. The northern shrimp biomass follows a similar trend to the total commercial invertebrate biomass. It is high during the late 1990s and 2000s, peaking at over 900 thousand tonnes, but decreases almost continuously in the late 2000s and 2010s to less than 250 thousand tonnes by 2015. Snow crab biomass fluctuates below 50 thousand tonnes across the graph with a slight increase in the late 2000s and then lower values in the 2010s. Text above the vertical bars on the left-hand side of the graph states “Invertebrates populations increased after the environment cooled and demersal fish collapsed”. A small, light blue outline-drawing of a shrimp is placed on the graph above the vertical bars on the right-hand side. Below the drawing there is text which states “Warming and predation caused a decline in invertebrates”.

Figure 36: The total fall survey biomass of benthic invertebrate species in 2J3K on the Newfoundland and Labrador Shelves along with individual invertebrate species survey biomass.

Figure 37: Spring survey biomass of benthic invertebrate species in 3LNO on the Newfoundland and Labrador Shelves along with individual invertebrate species biomass. A bar and line graph illustrates the fall survey biomass for benthic invertebrates (commercial species) as well as individual species for the 3LNO NAFO zones of the Newfoundland and Labrador Shelves. Text above the graph says “Newfoundland and Labrador Shelves 3LNO Spring Survey – Commercial Invertebrates Species”. The vertical axis on the left shows the scaled survey biomass index in units of thousands of tonnes from 0 to 300 in increments of 100. The bottom horizontal axis shows the years between 1995 and 2020 in 5 year increments. The biomass for commercial invertebrates species in the spring 3LNO survey is represented by grey vertical bars. The total survey biomass increases during the late 1990s and 2000s, peaking at approximately 300 thousand tonnes in 2007. It then declines reaching approximately 100 thousand tonnes by 2014. There is no data in 2015, but in 2016, the last year of data, it was lower again. The spring survey biomass for two benthic invertebrates species is represented by different coloured lines on the same graph. A legend appears on the right. A yellow data line illustrates the survey biomass trend for northern shrimp. A red data line illustrates the survey biomass trend for snow crab. The northern shrimp biomass follows a similar trend to the total commercial invertebrate biomass. It increases during the late 1990s and 2000s, peaking near 300 thousand tonnes. It decreases in the late 2000s and 2010s to less than approximately 25 thousand tonnes by 2016. There is no data for 2015. The snow crab biomass is around 50 thousand tonnes in the late 1990s, but decreases to less than 25 thousand tonnes by 2000 and remains at this level. There is no data for 2015, but the biomass in 2016 is lower again. A small, light blue outline-drawing of a shrimp is placed on the graph above the vertical bars to the left-hand side. Below the drawing there is text which states “Invertebrate populations increased after the environment cooled and demersal fish collapsed”. To the right-hand side of the graph, text above the vertical bars states “Warming and some increased predation has caused a decline in invertebrates.”

Figure 37: Spring survey biomass of benthic invertebrate species in 3LNO on the Newfoundland and Labrador Shelves along with individual invertebrate species biomass.

Figure 38: Survey biomass of individual demersal fish species in 3Ps on the Newfoundland and Labrador Shelves. A line graph illustrates the survey biomass for demersal fish species in the 3Ps NAFO zone of the Newfoundland and Labrador Shelves. Text above the graph says “Newfoundland and Labrador Shelves Survey of Demersal Fish in Area 3Ps”. The vertical axis on the left shows the scaled survey biomass index in units of thousands of tonnes from 0 to 150 in increments of 50. The bottom horizontal axis shows the years between 1995 and 2020 in 5 year increments. The survey biomass for each demersal fish species is represented by different coloured lines on the same graph. The data starts in 1996 and ends in 2017, but there is no data for 2006. A legend appears on the right. A dark blue data line illustrates the survey biomass trend for Atlantic cod. A black data line illustrates the survey biomass trend for black dogfish. A dark green data line illustrates the survey biomass trend for Greenland halibut. A light blue data line illustrates the survey biomass trend for other species. A blue data line illustrates the survey biomass trend for spiny dogfish. An orange data line illustrates the survey biomass trend for silver hake. A green data line illustrates the survey biomass trend for white hake. Atlantic cod has the highest biomass of species in the graph in most years. There is a peak at approximately 125 thousand tonnes in 1998, but it generally fluctuates between 25 to 80 thousand tonnes. It decreases from 2015. The other species generally stay below 10 thousand tonnes. The black dogfish biomass is near 20 thousand tonnes in the mid-1990s, but then decreases below 10 thousand toones and decreases again in the 2010s. The Greenland halibut is near 5 thousand tonnes throughout the timespan. Spiny dogfish is generally near or below 5 thousand tonnes with a couple of higher years in the early 2000s approaching 10 to 20 thousand tonnes. Silver hake is near 5 thousand tonnes until the 2010s when it begins to increase and fluctuates around 20 thousand tonnes with a peak of near 50 thousand tonnes in 2014. White hake is generally fluctuates around 5 thousand tonnes with a couple of years approaching 10 thousand tonnes in the early 2000s. A small, light blue outline-drawing of a silver hake is placed above the data lines near the middle of the graph. Below the drawing there is text which states “Previously uncommon species like silver hake are becoming more important”. An arrow points from the text to the orange line in the 2010s.

Figure 38: Survey biomass of individual demersal fish species in 3Ps on the Newfoundland and Labrador Shelves.

Marine mammals

Figure 39: Current population trends of marine mammals in the Northwest Atlantic. Many are unknown. A bar graph illustrates the current population trends of marine mammal species in the Northwest Atlantic. Text above the graphs says “Number of marine mammal species”. The vertical axis on the left shows the status in categories of increasing, stable, decreasing, and unknown. The bottom horizontal axis shows the number of marine mammal species from 0 to 25 in increments of 5. The number of marine mammal species for each category is represented by red horizontal bars. The number of species for each category from the top is 5 increasing, 2 stable, 3 decreasing, and 20 unknown.

Figure 39: Current population trends of marine mammals in the Northwest Atlantic. Many are unknown.

There are around 30 species of pinnipeds (seals and walruses) and cetaceans (whales, dolphins, and porpoises) found in the Northwest Atlantic. Many of the cetacean species are summer migrants, including fin whales, humpback whales, minke whales, many species of dolphins, and North Atlantic right whales. These seasonal species are thought to give birth and mate in temperate and tropical waters during winter. They then move north to feed in Canada’s Atlantic waters, mainly on capelin, Atlantic herring, and krill. Some marine mammals in the Atlantic are also found in the Arctic. These include species like the beluga whale, ringed seal, and Atlantic walrus. Migratory species such as harp and hooded seals, spend part of the year in the Arctic, but move southward to give birth (or pup) and feed.

The role of marine mammals in the Atlantic food web varies widely, from fish-eating grey seals to slow-moving, copepod- and fish-eating Northern Atlantic right whales. As many marine mammal species are highly mobile and migratory, their movements can reflect changes in prey or in environmental conditions.

Estimating how many marine mammals live in the Atlantic ecosystem, including their distribution, location, and behaviour can help scientists better understand the marine environment as a whole. Some species have been tagged to monitor their movements and diving behaviours using satellite telemetry. This leads to better understanding of their seasonal distribution and habitat use. For many cetaceans, sightings and occasional reports from boats and observers are the main clues to their locations. The first extensive survey of cetaceans along the Canadian continental shelf was carried out in 2007. Results from a second survey carried out in 2016 will help update these estimates in future reports.

Status and trends

Sea turtles

Figure 40: Seasonal movement of leatherback sea turtles through Canadian waters from 1999 to 2016 from satellite tags. The areas circled in orange represent high use areas (>50% of their time). Four maps stacked 2 by 2 of tagged leatherback sea turtle locations. Text above the graph says “Leatherback Sea Turtle Annual Movements”. Each map represents a season. The top left map is winter, bottom left is spring, top right is summer, and bottom right is autumn. Each map is the same and extends from 50°N latitude at the top to 10°N at the bottom and shows eastern North and South America from latitude with Newfoundland and Labrador at the top and Venezuela at the bottom. The bottom axis of each graph extends from approximately 80°W at the left to 20°W at the right where the western coast of Africa is visible. A legend appears at the right. The satellite tag locations from 1999 to 2016 are represented on the maps by green dots. High use areas, where turtles spend more than 50% of their time, and represented by areas outlined with orange and shaded blue. On the top left map of winter, lines of green dots extend from off the coast of North America down to South America. There is a blue shaded area on the southern coast of the United States. Another larger blue shaded area extends from the coast of Venezuela to the north and east with a smaller area approximately midway between South America and Africa. On the bottom left map of spring, there green dots extend from North America to South America. There is a small blue shaded area off the southern coast of the United States, and a large shaded area which extends from Nova Scotia down to Venezuela. On the top right map of summer, a large number of green dots are close to North America from the Gulf of St. Lawrence and the south coast of Newfoundland down the northeast coast of the United States. A few lines of green dots extend down to Venezuela in South America, and there are some shorter lines of green dots in the northern mid-Atlantic between 30°W and 40°W longitude. On the bottom right map of autumn, many lines of green dots extend between the east coast of North America and Venezuela out towards the middle of the Atlantic. A large shaded area extends from The Gulf of St. Lawrence and south coast of Newfoundland, down the east coast of North America and narrows as it extends southeast to the mid-Atlantic ending around 15°N latitude.

Figure 40: Seasonal movement of leatherback sea turtles through Canadian waters from 1999 to 2016 from satellite tags. The areas circled in orange represent high use areas (>50% of their time).

The most common sea turtles in Atlantic Canada are leatherback and loggerhead turtles. Both species are migratory, moving between beaches, nearshore coastal waters, and the open ocean in different life stages. Leatherbacks typically occupy Atlantic Canada, one of their most important foraging habitats, from June to December (Figure 40). They inhabit the sun-bathed zone of the ocean, spending most of their time in near-surface waters. This makes them vulnerable to fishing activity as bycatch. Young loggerheads are mainly seen during summer and fall in warm offshore waters. Most loggerhead turtle strandings have occurred in late autumn. The strandings were linked to cooling ambient ocean temperature and the onset of hypothermia.

Sea turtle eggs and hatchlings are subjected to high levels of predation in aquatic and terrestrial environments by a broad range of marine predators, including birds and fish. As such, sea turtles transport nutrients and energy between marine and terrestrial ecosystems. Leatherbacks also contribute to ecosystem balance in some areas by consuming jellyfish, which are a major predator of zooplankton and larval fish.

Leatherback turtles have been observed in high-use foraging areas off Nova Scotia every year since 2002. In-water sampling, application of identification tags, and telemetry studies have all provided insight into the population characteristics, movements, foraging behaviour, and habitat use of leatherback and loggerhead turtles.

Status and trends

Seabirds

Figure 41: Average percent change in population size since 1970 of 20 breeding seabirds in eastern Canada for which data is available. A line graph illustrates the change in population size for seabird populations in eastern Canada. Text above the graph says “Seabird Populations”. The vertical axis on the left shows the average percent change since 1970 from -50% to 200%. The bottom horizontal axis shows the years from 1970 to 2020 in increments of 10. The average percent change in seabird populations is represented by a blue data line with a shaded blue area above and below the data line representing the confidence interval. The trend in average percent population size starts at 0% in 1970 and increases to above 50% in the 2010s.

Figure 41: Average percent change in population size since 1970 of 20 breeding seabirds in eastern Canada for which data is available.

Figure 42: Of 20 seabird species for which data is available, the number of species that have increased or decreased in population since 1970. A stacked bar graph of the number of seabird species which have increased or decreased in population since 1970. Text above the graph says “Seabirds”. The vertical axis on the left is the number of species. The top of the graph represents the number of species which have increased since 1970 and extends upward from 0 to 12. The bottom of the graph represents the number of species which have had decreased since 1970 and extends downwards from 0 to 12. Three coloured bars are stacked on the top graph. A green bar extends to 1 and represents species which have shown a small increase. On top of this a blue bar extends up to 3 and represents species which have shown a moderate increase. A darker blue bar extends up to 12 and represents species which have shown a large increase. Three coloured bars are stacked and extend downwards on the bottom graph. The top yellow bar extends down to 2 and represents species which have shown a small decrease. An orange bar extends down to 6 and represents species which have shown a moderate decrease. A red bar extends down to 8 and represents species which have shown a large decrease.

Figure 42: Of 20 seabird species for which data is available, the number of species that have increased or decreased in population since 1970.

More than 20 different species of seabirds breed on the eastern Canadian coastline. An additional 40 species from the Arctic, Europe, and even South America feed in the region. Their total number is estimated in the tens of millions during certain times of the year.

Seabirds are one of the most visible components of the marine landscape. As top predators and excellent samplers of the marine environment, seabirds can be effective indicators of overall ocean health.

Seabird population trends are measured through systematic surveys. This is done by counting all individuals or nests of entire breeding populations at all sites or selected key sites. It is also done through plot surveys that sample a representative portion of the colony. Aerial surveys provide the most cost-effective way of conducting a comprehensive population estimate of ground-nesting seabirds (for example, gulls, terns, and gannets). Ground surveys are required to sample burrow or crevice-nesting seabirds (like puffins and storm-petrels). Cliff-nesting seabirds (such as alcids and, kittiwakes) are best counted by boat.

Status and trends

Aquatic invasive species

Aquatic invasive species (AIS) are considered competitive organisms that establish themselves in a new environment that lacks their natural predators. This favours their rapid growth or reproduction. AIS can threaten aquatic ecosystems by occupying habitats and out-competing native species. AIS introduction and spread can occur naturally by larvae or fragments drifting in water currents. It can also occur through human activities, including commercial shipping, recreational boating, aquaculture and fishing activities, animal and aquarium trades or by intentional introduction. Some species of ascidians (non-native tunicates) and the European green crab are the most prolific and troublesome of the non-indigenous invaders along the Atlantic Canadian coast.

The negative impacts of invasive species on Atlantic Canadian marine ecosystems include declines in abundance and biomass of estuarine fish communities, declines in eelgrass and kelp biomass, and shifts in community structure for some benthic invertebrates. Invasive species can also have negative consequences for commercial fishing and aquaculture industries.

The DFO Atlantic Zone AIS Monitoring Program uses standardized methods to monitor biofouling species. It conducts research related to the impacts and mitigation of AIS in the Atlantic.

Status and trends

Everything is connected

The Atlantic Ocean ecosystems are a complex ecological network. It weaves biological components with the physical and chemical characteristics of the environment. This interconnected ocean network requires careful study using ecosystem-based approaches to scientific research and monitoring.

The interconnected relationship between organisms and processes in the Atlantic Ocean ecosystems are changing. The changes are occurring both naturally and through human influences. Real change is occurring in ocean food webs. The types of species, their location, habitat, and diet are shifting at different rates and scales alongside physical changes in the marine environment.

These changes include rising sea-surface temperatures, ocean acidity, and hypoxic events. They also include an increase in the biomass of many species such as American lobster and Atlantic halibut, and seals. Warm-water species and aquatic invasive species are moving in, and other species, such as North Atlantic right whales, are changing their distribution.

Canada’s Atlantic Ocean is experiencing a loss in sea ice as well as declines in the abundance of Atlantic cod and herring. Some populations of seabirds like herring gulls and black-legged kittiwakes are declining too. Endangered North Atlantic right whales, blue whales, leatherback and loggerhead turtles are struggling in numbers. Some species are recovering and thriving. These include populations of seabirds such as common murres and Atlantic puffins. Conditions of natural habitats are in flux alongside shifts in phytoplankton blooms and zooplankton community structure. These complex changes are all interconnected. Understanding the influence of climate change, human pressures, and natural variability is essential.

Ongoing monitoring and research of the ocean environment and the organisms that inhabit Atlantic marine ecosystems will continue to help uncover how our marine ecosystems are connected and how they are changing. It will also help to improve management and conservation measures.

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