Study: Fish heading to cooler waters
By Doug Fraser | www.capecodtimes.com
A new study finds that species such as codfish, above, and flounder are searching for cooler water. That could mean they're concentrated in smaller areas that have more natural predators, less food resources and be eaiser to fish. Photo Credit: Steve Heaslip from Cape Cod Times files.
A recently released study showed that, like most natural processes responding to climate change, fish adaptation to a warming ocean is nuanced. Fish aren’t simply heading toward the poles to find cooler water, the study found, but also moving west toward shore, seeking out the chillier bottom water in the deep basins of the Gulf of Maine.
Published Feb. 22 in the online journal PLOS ONE and led by Janet Nye, a postdoctoral researcher at the Northeast Fisheries Science Center in Woods Hole, the study differed from previous efforts at tracking single species, and instead followed groups of species with similar environmental preferences, including water temperature. In doing so, researchers had more confidence that the shift in where fish were being found was because of warming water temperatures and not fishing pressure or food availability.
This may have profound implications for fisheries management, affecting everything from population estimates to allocation of quota, as fish species such as cod and flounder with relatively low population levels squeeze into smaller areas that may have more natural predators, less food resources, and be easier to fish.
“There appears to be a concentrating effect, which may not be very desirable. It would make them more vulnerable to being caught,” said Michael Fogarty, the chief of the ecosystems assessment program for the science center in Woods Hole.The ocean is heating up faster in the Northeast, and at 1/5 of a degree Fahrenheit per decade, it is the highest rate of anywhere in U.S. waters and one of the fastest-warming areas in the world. Fish, which are cold-blooded, are more stressed physically and more susceptible to disease as water temperatures increase. They also spend less time eating and more time trying to find places that are cool enough for their metabolism.
A 2014 study of 350 species of fish on the East and West coasts by Rutgers University biologist Malin Pinsky showed that those fish were generally headed north in response to higher water temperatures. In general, single-species studies in the Northeast found fish heading north and further offshore to find that optimal water temperature.
That may be true for those fish located southeast of Cape Cod on Georges Bank and on the equally flat and shallow continental shelf off the Mid-Atlantic states, where higher temperatures have driven many species north over the past 50 years. But north of the Cape, retreating glaciers scoured the bedrock of the Gulf of Maine, creating a combination of deep cold basins, surrounded by shallow, fertile sunken landmasses, like Georges and Brown banks. Some fish species have taken a turn toward the shore, seeking out the cooler water but also increasing their likelihood of being caught.
In this rapidly changing ecosystem, researchers found one constant: the fish always sought water of a certain temperature whether that meant going deeper or heading north. These species all moved as a group to similar places, seeking the optimal temperature.
Studies reinforcing the hypothesis that fish are rapidly responding to climate change, and the implications of that trend, are beginning to pile up. Last month, Jon Hare, a fisheries oceanographer at the fisheries science center, published a study that assessed 82 fish, shellfish and other species considered valuable to commercial and recreational fishermen and those listed as endangered or ecologically important for climate change vulnerability. Cod and yellowtail flounder were considered less vulnerable because they can exist in a variety of habitats and eat a wide array of prey. But scallops, the single most valuable animals harvested in New England, were found to be very vulnerable because of their specific niche habitat and prey. The study found that a majority of these species have already moved because of warmer waters and that this trend would continue.
The big question now is how fishery management will incorporate these studies and use them to adopt regulations that reflect these biological realities.
“One of the things we want to do is to step back one level and look at the big picture,” Fogarty said. Fishery managers seeking to rebuild and maintain fish stocks at sustainable levels for commercial and recreational fishermen need information that can be used in the planning process.
“When we see a lot of species behaving in the same way, it strengthens the evidence that something is going on and we need that to be taken into account,” Fogarty said.
But the New England Fishery Management Council, a representative body of fishermen, state and federal fishery officials and industry representatives, needs quantifiable data to draw up fishery management plans. Climate change is happening relatively quickly, said council member John Pappalardo, of Chatham, and the council process is deliberative and often slow to react to new information.
"The environment we're fishing in has changed a lot over the last 15 years. The assemblage of fish species is different," Pappalardo said. "The question is, is that environmentally driven, and if so, where is the environment driving it to?"
"There's a lot of questions and not a lot of answers," he added.
“How can we take those pieces and put it together the way we do stock assessments?” said fishery council spokeswoman Pat Fiorelli. “We are not there yet in terms of a mechanism to incorporate them into a plan.”
But the council and the National Marine Fisheries Service are both looking at ways to incorporate climate change into the regulatory framework. Pappalardo is the chairman of the council’s ecosystem-based fishery management committee that is looking at the impact of climate change, Fiorelli said. Council staff is working on developing a model of a fishery management plan that will incorporate climate change.
NMFS also unveiled its climate change strategy this summer that they hoped would be a blueprint to discovering and using climate-related information to advise fishermen and other marine-dependent stakeholders and design ways to adapt and manage resources.
“The main thing for us is to remain adaptable and try to preserve as many options on the biological, economic, and human and fish management sides of this,” Fogarty said.
— Follow Doug Fraser on Twitter:@dougfrasercct.