A Marine Institute researcher is the lead author of a scientific paper that examines the impact of shifting northwest Atlantic Ocean climate conditions on groundfish stocks, such as northern cod.

The paper states that shifting environmental conditions contributed to the rise and decline in fish populations over the past 75 years.

Warm and cold

Using decades of climate and fisheries data dating back to 1950, Dr. Frédéric Cyr and seven Fisheries and Oceans Canada co-authors found that the northwest Atlantic experiences shifting climate phases that can range from three to 20 years.

These climate phases, which can be classified as warm and cold, influence both ecosystem productivity and fisheries of groundfish species.

Ecosystem productivity refers to the rate at which species biomass is generated in an ecosystem.

The researchers say the warm and cold phases also impact phytoplankton and zooplankton that fish populations rely upon for food.

For instance, during warmer phases in the ocean ecosystem off Newfoundland and Labrador, the density of phytoplankton and zooplankton was higher than during colder phases.

The journal Nature Communications published the paper, titled Environmental Control on the Productivity of a Heavily Fished Ecosystem, on June 6.

"The ocean climate of the northwest Atlantic changes in cycles and these cycles impact the fish stocks,” said Dr. Cyr, a research scientist with the Marine Institute’s Centre for Fisheries Ecosystems Research. "The frequency of these cycles seems to have increased in recent decades, which may have slowed down the recovery of some groundfish stocks after the 1990s collapse.

"Tracking these climate shifts offers a powerful tool for risk assessment and adaptability in fisheries management, for example, by reducing the fishing pressure when the climate is negatively affecting the stocks,” he added.

Contributed to northern cod collapse

Dr. Cyr is a former scientist with Fisheries and Oceans Canada; he started the research paper with his seven co-authors while working at the Northwest Atlantic Fisheries Centre in St. John’s.

While overfishing was a significant factor in the collapse of northern cod, the paper states that environmental factors also contributed to the collapse and may explain the lack of recovery more than 30 years later.

“The collapse of groundfish stocks occurred during one of the coldest periods of the last century in the northwest Atlantic and coincided with the collapse of capelin, a key pelagic forage fish species for Newfoundland and Labrador's ecosystems, and several groundfish species that were not subject to directed commercial fishing. Similar cold conditions occurred in the mid-2010s, which did not help the recovery," said Dr. Cyr.

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For more information, please contact Madeline Meadus, communications, Marine Institute, at madeline.meadus@mi.mun.ca or 709-327-7578.