Follow the Fish | As Waters Warm Species Are on the Move

Like detectives following leads, fishermen follow sea temperatures. The rise and fall of the ocean’s warmth offer clues to where fish hide. But rising average sea temperatures have made tracking and catching fish more complex.

“Climate change is real, and it is real in the ocean,” says commercial fisherman Richard Fuka, who heads the R.I. Fishermen’s Alliance. “Fishermen are throwing their old logbooks out the window.”

In his 2015 State of the Union address, President Barack Obama called climate change the greatest threat to future generations. The statement came four days after NASA reported that 2014 was the warmest year since 1880, and that average surface temperatures increased 0.8°C in that timeframe. NASA blamed the trend primarily on increased carbon dioxide and other human-driven emissions.

For the world’s oceans, rising temperatures matter. The United Nations Intergovernmental Panel on Climate Change concluded with “high confidence” in 2014 that freshwater and saltwater fish are adjusting migration patterns in response to changing sea temperatures. Worse, some species face higher mortality rates and others could become extinct.

“This is going to change things, no doubt,” says Fred Mattera, a retired fisherman who heads the Point Club, a Rhode Island-based fishing insurance cooperative.

The United Nations report warned that climate change is already impacting the chemistry of the ocean, from the salt content to acidification. Areas with little oxygen are expanding in the tropical Atlantic, Pacific, and Indian oceans because warmer water contains less dissolved oxygen than colder water, which in turn limits where fish thrive. Coral cover that provides an important home for marine species has diminished and may be growing at a slower rate. In short, the entire ecosystem is transforming.

“The change in temperature is changing the way the energy is processed in the food web,” says Jeremy Collie, a professor of oceanography and a fish expert at the University of Rhode Island Graduate School of Oceanography. “It’s tipping the balance from one species over another and results in there being winners and losers in the food web.”

A study by Collie and his colleagues found between 1959 and 2005 an increase of 1.6°C (2.9°F) in Narragansett Bay. The same study showed shifts in the population of at least 24 species of fish. By measuring fish catches at stations in lower Narragansett Bay and Rhode Island Sound, researchers found a swing to pelagic (water-column) fish and squid from demersal (bottom-dwelling) fish.

South of Whale Rock in Rhode Island Sound, URI researchers recorded more than a 100-fold drop in cunner. Red hake, longhorn sculpin, sea stars, and silver hake all experienced drops of more than 50 percent. Conversely, a more than 100-fold increase in butterfish, striped sea robin, and long-fin squid, which prefer warmer waters, came along with the upswing in temperature.

A shift in temperatures and species extends to the larger Gulf of Maine, the vast expanse of water between Cape Cod and Nova Scotia that many Northeast fishermen call home. Situated between two ecosystems—the colder North Atlantic and the warmer mid-Atlantic—rising temperatures threaten to push out the fish that prefer chillier temperatures.

The Gulf of Maine Research Institute found that temperatures in the gulf are rising faster in recent years than they have over the past three decades. Comparing it against a global dataset, researchers discovered a worrying trend: over the past decade, waters in the gulf warmed faster than 99 percent of the world’s oceans.

Kathy Mills, an associate research scientist at the institute, says that integrating knowledge of sea temperatures with fisheries policy is crucial to ensuring a sustainable fishing industry.

“We’re starting to see ways in which thinking about temperature really could have some immediate effects on the science that guides fisheries management,” Mills says.

Federal law requires regional fisheries management councils to implement policies—usually boiling down to catch limits—that rebuild stocks within a decade. To do that, scientists need to understand the mortality rates of species, and they are finding temperature—as well as fishing—affects that rate. Mills says temperature changes may stunt fish growth and small fish may lay fewer or less viable eggs.

“I think we’re just starting to crack the surface of really understanding some of these changes and using them to look ahead to what things might look like in the future,” Mills says.

Owners of party and charter fishing boats already have some idea what that future may look like. Twenty years ago they saw cod all but disappear from the region. Once a year-round industry that primarily chased cod, charter fishing had to change to a seasonal business that diversified among species.

“We tend to be an innovative group of fishermen in Rhode Island, and we will adapt to whatever happens,” says Rick Bellavance, president of the 65-member Rhode Island Party and Charter Boat Association.

Rhode Island Commercial Fishermen’s Association President Christopher Brown, who’s been fishing since 1976, agrees. “Everyone assumes that climate change is going to produce an infinite list of losers biologically, but I don’t see that being plausible,” he says. “It’s simply going to increase the stocks for some species.”

If the public demands those species, fishermen will chase them. Brown says some in the industry grumble about spending money to purchase new nets or other equipment to catch a new species. However, the industry long ago learned it must stand ready to rapidly adjust in the face of tightening government regulations and the shifting taste buds of Americans, he says. But Bellavance and his commercial fishermen counterparts say they also need regulations to change with the changing sea temperatures.

The National Oceanic and Atmospheric Administration (NOAA) is trying to do just that. NOAA collects the data on fish populations that serve as the basis for fisheries management policy. Under pressure from the fishing industry and public to refine its models, NOAA started examining how to incorporate temperature data into its formulas, says Jason Link, a top fisheries scientist at the agency.

“We’re really taking a look at the effects of how temperature is changing in the ocean and how it relates to all of our trust species [the species NOAA is charged with overseeing], not only the groundfish but also protected species and even species that are ecologically important,” Link says. “The Northeast region was the first to pilot climate vulnerability analysis to see which species would be most vulnerable to temperature and other changes.”

Scientists continue to compile the results of that analysis. In the meantime, Link says NOAA successfully factored climate change into its stock assessment of butterfish. A scientist in a New Jersey NOAA Fisheries Laboratory worked with university colleagues, commercial fishermen, and others to revise the assessment. The research played a role in the Mid-Atlantic Fishery Management Council’s decision to increase catch limits of the species.

Link says all the regional councils will soon see assessments that account for temperature change because it’s occurring throughout U.S. waters with varying consequences. For example, in the Gulf of Mexico, species attempting to escape warmer waters by moving north are stemmed by land. So instead they head to deeper or more western waters. In Alaska, melting sea ice changes the salinity in the water and shifts temperatures, putting some species at risk.   

“We need to step back and provide broader context and more regularly do more of these vulnerability analyses,” Link says. “Then we can begin to prioritize and develop mitigation strategies and emphasize how to respond to some of these changes that will be beyond our ability to control.”

Implementing those strategies may be a challenge. More than three decades of fisheries management set catch limits and developed days-at-sea regulations that some fishermen complain ruin their livelihood. In the Northeast, an unsuccessful plan to rebuild the iconic cod stock left many fishermen skeptical of both government intervention and the science behind it.

Brown says fishermen are willing to limit their hauls if it means protecting their long-term survival.

“But as it is right now we have very little faith in the science,” behind the catch limits set by the New England Fishery Management Council and its regional peers, he says.

Any adjustment in quotas or days-at-sea regulations inevitably causes controversy. Few researchers think that climate change will mean the end of all fish, but Mills, from the research institute, worries a shift in species will introduce new questions about fairness.

Currently, aforementioned regional fisheries councils enforce fisheries policies. Councils typically set catch limits and award licenses on a regional basis. When a species leaves the human-drawn regulatory zone, perhaps because of temperature changes, fishermen may not be allowed to follow them into the next zone.

“It creates these really difficult questions about how you deal with fairness and equity,” Mills says.

Should local councils allow in fishermen from outside their home regions? What about fish that transverse international boundaries or head into non-exclusive fishing zones? These are tough questions that regulators are just now considering in  the face of species permanently moving.

To try to answer those questions, the New England Fishery Management Council has hosted workshops with stakeholders and started discussing possible solutions internally. Still in the early stages of discussion, one possible solution is to reach compacts with its neighbor, the Mid-Atlantic Fishery Management Council, on regulations. Chris Kellogg, the council’s deputy director, says new information on climate change has also spurred the council to look at species management with a wider lens.

The council “supports the research underway on the issue and is working on ways to use that information to evaluate changes that might be relevant to the fisheries it manages,” he says. “In the larger context, work continues on an ecosystem-based fisheries management program that will examine New England fisheries spatially across all fish species rather than on a single-species basis.”

“Millions depennd on the ocean for food.”