Climate study underscores challenge of managing Gulf of Maine fisheries

Courtesy / Gulf of Maine Research Institute This chart shows the sea surface temperature trend in the Gulf of Maine from 1982-2013. The blue line and black dots show, respectively, daily and annual sea surface temperature anomalies in that period. The black dashed line shows the long-term trend, and the red solid line shows the trend from 2004-2013.

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By Laurie Schreiber

Incorporating climate change and its effects on marine life will be an important part of sustaining key fisheries in the Gulf of Maine that already are proving difficult to manage.

That’s the thinking behind a new study by the Gulf of Maine Research Institute in Portland, which received a $1.1 million grant from the National Oceanic and Atmospheric Administration to investigate impacts of climate change on groundfish and examine how fisheries management practices might be improved to account for climate change impacts.

Over the course of the last decade, the Gulf of Maine has warmed faster than 99% of the global ocean, said GMRI research scientist Lisa Kerr, the study’s lead researcher. The project also includes collaborators from NOAA, the University of Massachusetts/Dartmouth’s School for Marine Science and Technology, and GMRI scientist Andrew Pershing.

According to a 2015 GMRI study published in the journal Science, the warming has led to reduced numbers surviving to adulthood and increased mortality in the region’s Atlantic cod stock. That’s a primary factor in the failure of cod to rebound, despite fishermen’s adherence to strict management policies, according to the study.

The scenario is complicated by the fact that fisheries managers don’t account for temperature impacts as they evaluate fish stocks, according to a press release from GMRI. Instead, the targets for allowable harvest are set based on historic data — which sometimes fails to reflect the present reality in the Gulf of Maine.

Gulf of Maine rapidly warming

Reached by phone, Kerr explained that the Gulf of Maine is warming more rapidly than the rest of the world’s oceans in part due to atmospheric warming and in part because shifts in ocean circulation are keeping warm water in the region for longer periods of time.

“It makes working in our region particularly challenging, because we’re dealing with a lot of change really fast, and sometimes our fishery management isn’t able to keep pace,” she said.

Warming water has brought shifts in the distribution of species and in their productivity, she said. Research shows that cod productivity, for example, has decreased in recent years.

“The production of young cod has decreased in relation to increasing temperature,” she said. “That will ultimately impact how many adults there are and how many fish you can catch.”

Interestingly, she said, other species, like haddock and pollock, have been increasing in abundance.

“Our work is going to look at ways to better estimate the number of fish that are out there, how a species is responding to climate change, and ways to harvest that might be more climate-responsive,” she said. It will also likely affect how fishery managers come up with target numbers for rebuilding depleted fish stocks, she said; those numbers are currently based on historical levels of fish abundance.

“But a lot has changed and a lot of those populations might not be able to be as productive in warmer water,” she said. “So we need to consider how much can we really fish on cod in warming conditions. Whereas with haddock, we might be able to catch more if they’re responding well to climate change.”

In addition to identifying climate change impacts on key commercial species and evaluating new approaches to adapt fisheries management to account for climate change, the three-year study will project potential economic and ecological impacts of these new approaches.

The research team will use advanced computer modeling to evaluate potential “climate-responsive” fisheries management strategies. The models will use on-the-water data to compare today’s management strategies to alternative strategies that account for climate change. The team plans to develop an interactive web-based portion of the study to get input from fishermen.