Using decades of climate and fisheries data dating back to 1950, Dr. Frédéric Cyr and seven co-authors with Fisheries and Oceans Canada found that the Northwest Atlantic experiences shifting climate phases that can range from three years 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 paper says the warm and cold phases also impact phytoplankton and zooplankton that fish populations rely upon for food. During warmer phases in the ocean ecosystem off Newfoundland and Labrador, for instance, the density of phytoplankton and zooplankton was higher than during colder phases.

Entitled “Environmental control on the productivity of a heavily fished ecosystem,” the paper was published June 6 in the journal Nature Communications.

“The ocean climate of the Northwest Atlantic changes in cycles and these cycles impact the fish stocks. 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,” said Dr. Cyr, research scientist with the Marine Institute’s Centre for Fisheries Ecosystems Research.

“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.”

Dr. Cyr is a former scientist with Fisheries and Oceans Canada. He co-authored this research paper with Drs. Aaron Adamack, David Bélanger, Mariano Koen-Alonso, Darrell Mullowney, Hannah Murphy, Paul Regular and Pierre Pepin.

Dr. Cyr also published an accompanying blog post to the research paper.

While overfishing was a significant factor in the collapse of Northern cod, the paper says environmental factors have 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 for 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 NL 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.”