Probing key connections in the Newfoundland and Labrador marine ecosystem

“For the first time in many years, at least since the moratorium on Atlantic cod fishing in 1992, there are signals that Newfoundland groundfish stocks may be at the beginning of a recovery process,” says DFO research scientist Dr. Mariano Koen-Alonso of the Northwest Atlantic Fisheries Centre in St. John's, Nfld. The coordinator of DFO's Newfoundland Ecosystem Research Initiative (ERI) speaks those words cautiously, adding that “it's too early to tell whether small improvements in some stocks over the past few years will become a full-fledged recovery or if it's just a handful of good years. Numbers are still well below pre-collapse levels but there's a positive signal nonetheless.”

“What's clear is there are really interesting changes going on in the ecosystem right now that we need to pay close attention to,” he says. “The ecosystem may be on the brink of a reconfiguration but we don't have a long enough time series of data to know yet which direction it's going in.”

Although some groundfish stocks have shown positive trends, there are mixed signal for capelin, a key forage species. The goal of the Newfoundland ERI is to begin unravelling the connections between these and other species to gain a better understanding of how the ecosystem works.

Integrated ecosystem research

Building on historic data and ongoing surveys for other fisheries research initiatives, the Newfoundland ERI (2007-2012) will improve and expand the monitoring and collection of data to develop a holistic view of the region's ecosystem. The project, part of DFO's national ERI, is a collaborative effort involving scientists from all research divisions in the department's Newfoundland and Labrador Region, some DFO Centres of Expertise and colleagues at Memorial University.

“We need to know much more than we did in the past to move toward integrated species management — ‭understanding how the way we manage one species will affect the way we need to manage other species based on our knowledge of the ecosystem,” says Dr. Koen-Alonso. New data collection will focus on key forage fish and non-commercial species, the structure of the fish community, including changes and trends, the nature and pattern of key components of bottom-dwelling communities, and key species interactions.

Key ecosystem connectors

The team is reanalyzing old data in novel ways to determine trends and patterns in the fish community. Both historic and new data will also be integrated into population dynamic and ecosystem computer models to determine the key connections between different species and components of the ecosystem. Identifying the key connections and drivers of the ecosystem will also guide which elements should be monitored and assessed on an ongoing basis.

The project will also explore the effect of human activities and stressors (in addition to fishing) on the ecosystem. For example, projected changes and variability in temperature will be included in the computer models in an effort to explore the long-term effects of climate change on ecosystem dynamics and the composition of fish communities.

A foundation for future decision making

“The novelty of this research is integration, which will provide us with a longer-term vision of how we can expect the ecosystem to change and set the stage for long-term studies and large-scale ecosystem management,” says Dr. Koen-Alonso. “It will also provide a much better platform for determining the best management strategies for the future.”

Northern cod and capelin: preliminary findings

To date, the team has initiated improvements in species sampling, analyzed available data for fish community trends, and embarked on a comparative dietary analysis of top predators, including cod, turbot and harp seals. This analysis is already pointing to some interesting changes underway related to capelin and some groundfish stocks, including northern cod (one stock of Atlantic cod).

The collapse of commercial and non-commercial fish stocks in Newfoundland and Labrador during the late 1980s and early 1990s was more dramatic in northern regions. This was accompanied by an increase in harp seals and shrimp and, in the early 1990s, a dramatic decline in capelin, which are important prey for Atlantic cod.

“Most cod stocks are still in dire straits, however the northern cod stock has recently shown very modest improvement in numbers,” says Dr. Koen-Alonso.” It's a positive signal, but it doesn't mean in any way that the stock has recovered because the population is still less than 10 percent of what it was before the collapse. But five years ago, it was below five percent.” Several other groundfish species, including American plaice, have also shown some improvements in numbers over the past five to six years.

Capelin, which also declined dramatically in the early 1990s, began to show a slight recovery between 2003 and 2007 but declined again in 2008 and 2009. In addition, the timing of capelin spawning in 2009 has been the latest recorded in many areas. “This could have serious negative consequences for the survival of this year class,” says Dr. Koen-Alonso.

These fatty, energy-dense fish are key prey for cod and other groundfish and a critical connector between primary and secondary production (zooplankton and phytoplankton) and the upper levels of the marine food web, including large fish, marine mammals and seabirds. “The increase in capelin from 2003 to 2007 may have been a key factor in the recent positive signals for cod and other groundfish since the energy boost from feeding on capelin could improve their reproductive success and survival. This shows us that knowledge of capelin is critical to understanding how the ecosystem is going to develop,” he says.

Increases in capelin until 2007 may have been driven by changes underway lower in the food chain such as more zooplankton. The Newfoundland ERI is exploring these connections by collecting and analyzing the stomach contents of capelin and other forage and groundfish species.

“The fact that we've seen positive signals in more than one species tells us that we should pay very close attention to what's going on because we may be at a very good moment to help stocks recover if we're careful about what we do,” he says. “Also, the more recent declining trend in capelin may provide us with the type of contrasting information necessary to understand how these species are effectively connected, but it also highlights the potentially fragile nature of the positive signals for groundfish. We are not out of the fog yet.”

Common signals among species mark changing ecosystem

“Today we know that climate change, environmental factors and species interactions are as big a driver in marine ecosystems as fisheries catches and other human activities, so we need to factor the effects of all these ecosystem drivers into management plans,” says Dr. Koen-Alonso. The ecosystem approach enables scientists to pick up on common signals and trends in a set of species.

“Common signals tell us that something else in the ecosystem is changing and that the way we managed a given species in the past may not be sustainable right now,” he says. “That's the type of advice we expect integrated ecosystem analysis will be able to provide.”