Research Document - 2013/032

State of physical, biological, and selected fishery resources of Pacific Canadian marine ecosystems in 2012

By J.R. Irvine and W.R. Crawford

Abstract

This report summarises results from the fourteenth annual workshop on the state of physical, biological, and selected fishery resources of primarily Pacific Canadian marine ecosystems.

The global temperature in 2012 was warmer than the 20th century average almost everywhere, but not in the northeast Pacific Ocean where cool waters have been present in almost every year since 2007, part of a Pacific-wide weather pattern associated with La Niña conditions of these years.

Sea surface measurements from shore stations along the coast of British Columbia and in the Salish Sea, confirm that ocean conditions were cooler in 2012 than in 2011 and 2010. Preliminary results of measurements by a Continuous Plankton Recorder through the eastern Gulf of Alaska were partially processed at press time, revealing somewhat lower biomass of large diatoms (a type of phytoplankton) than usual, and much larger biomass of copepods. Both these results are compatible with cool ocean surface waters. Satellite imagery results detected a very strong bloom of coccolithophores west of northern Vancouver Island in June 2012, the strongest bloom of the 11-year record.

An intense bloom of phytoplankton was observed by MODIS (Moderate Resolution Imaging Spectroradiometer) satellite in the Gulf of Alaska more than 200 nautical miles west of Haida Gwaii in August 2012. Its location, size and intensity suggest it may have been due to fertilization of the ocean with iron-rich material, as part of a project undertaken by the Haida Salmon Restoration Corporation.

Albacore Tuna catches in Canadian waters increased in 2012 relative to the previous year, but were probably related to increased effort. Off the west coast of Vancouver Island, the zooplankton community contained more cool-water zooplankton than average, which is associated with good local survival and growth of young salmon and other fish as well as plankton-eating seabirds including Cassin’s Auklet. Walleye Pollock and Smooth Pink Shrimp densities increased in 2012, while Eulachon, Herring, and Sardine numbers remained relatively low. Nearshore fish populations in eelgrass and kelp beds of Pacific Rim National Park Reserve tend to vary more among areas than years.

Non-Fraser southern Sockeye Salmon stocks continued to exhibit re-building while those from the central and north coast continued a decadal-scale, sub-average return trend through 2012. The number of Pink Salmon returning in even-numbered years, including 2012, tend to be stable while populations returning in odd years, including the Fraser, are generally increasing. In 2012, juvenile Chum, Sockeye, Coho and Chinook Salmon catch rates were generally higher off the west coast of Vancouver Island (WCVI) and in the central coast than in 2011, and at or above the 1998-2012 long-term average for all species.

Waters of the Salish Sea, comprising Juan de Fuca Strait, Puget Sound and the Strait of Georgia and adjacent waters, host a separate ecosystem from offshore waters. A detailed study of Puget Sound waters since 1998 revealed systematic changes, many of which were due to intrusions of oceanic water.  For instance, the average oxygen content of Puget Sound waters below 20 metres depth varies with the upwelling index off the west coast of Washington State. Oxygen concentration declined in the past 5 or so years, although it rebounded in 2012. A longer time series is available for the Strait of Georgia, where oxygen concentration in deep waters over the past 40 years declined, attributed to similar declines in deep waters on the continental shelf that advect into the Strait. This decline in oxygen is of concern because oceanic sub-surface water in our region that is deficient in oxygen is often more acidic, and ocean acidity will increase everywhere as more carbon dioxide is added to the atmosphere.

Phytoplankton in the Strait of Georgia bloom in the late winter and early spring, reaching a peak when they have consumed all nutrients in the surface layer. The timing and duration of this peak of the spring bloom is believed to impact the survival of juvenile salmon and herring. The spring bloom of phytoplankton in the Strait of Georgia in 2012 was later than normal and similar in timing to the previous 6 years.

Juvenile salmon from the Fraser River generally enter the Strait of Georgia from April to June, many remaining there until the fall. A multi-year study of tagged sockeye salmon smolts exiting Chilko Lake in the Fraser River watershed found consistent early survival patterns among years. Tagged fish moved rapidly through the Strait of Georgia and Queen Charlotte Strait. Large catches of two-year-old juvenile Sockeye Salmon in research trawl surveys in the Strait of Georgia in 2012 resulted from record high returns to the Fraser River in 2010. Based on these research surveys in 2012, good returns are forecast for Fraser River Sockeye Salmon returning in 2014, and Coho and Pink Salmon returning in 2013, while poor returns of Chum and Chinook Salmon are expected in 2013 and 2014.

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