Warming waters and migrating fish stocks could cause political conflict

Climate change is driving fish species to migrate to new areas, and in the process they’re crossing political boundaries – potentially setting up future conflicts as some countries lose access to fish and others gain it, according to a recent study published in the journal Science.

Already, fish and other marine animals have shifted toward the poles at an average rate of 70 kilometers per decade. That rate is projected to continue or even accelerate as the planet warms.

When fish cross into new territory, it might prompt competitive harvesting between countries scrambling to exploit disappearing resources.

“Conflict leads to overfishing, which reduces food, profit, and jobs that fisheries can provide, and can also fracture international relations in other, non-fishery sectors,” Malin Pinsky, the lead author of the study and an assistant professor of biology at Rutgers University, told SeafoodSource.

The study looked at the distribution of nearly 900 commercially important marine fish and invertebrates, examining how their movements intersect with 261 of the world’s Exclusive Economic Zones. By 2100, more than 70 countries will see new fish stocks in their waters if greenhouse gas emissions continue at their current rates.

Cutting greenhouse gas emissions could reduce the scale and number of these migrations by half or more, Pinsky said.

Conflict over shifting fish stocks is not unheard of. In the 2000s, migrating mackerel in the northeast Atlantic caused such a rift between Iceland and other nations that it played a role in derailing attempts to join the European Union. In the eastern Pacific, a bout of warm ocean temperatures in the 1980s and 1990s shifted salmon spawning patterns, prompting a scuffle between U.S. and Canada.

Pinsky listed the United Sates, Iceland, Britain, Russia, and countries in East Asia as some that will have to start sharing significantly more. 

“I worry in particular about East Asia, where maritime relations are already tense over disputed borders,” Pinsky said.

Many countries may end up getting up to 30 percent of their catch from new fisheries that have migrated into their exclusive economic zones by 2100, according to the study. Australia and fisheries around the Bering Sea may get an even higher percentage.

But tropical countries seem likely to suffer significantly, since fish will move out and others won’t move into the replace them.

“Fish in general are moving to higher latitudes, which means new species aren’t moving into countries near the equator,” Pinsky said. “We think that means there will be fewer fish in the tropics, but we don’t know for sure yet.”

Some species might adapt to warmer waters, and some evidence suggests that is likeliest to happen in the tropics, where fish won’t also have to compete with new species, Pinsky said. “However, we don’t yet know if they can adapt fast enough to keep up with rapidly warming waters,” he said.

The Gulf of Maine is already experiencing major migrations. Lobster are moving towards Canada, cod are shifting deeper, and black sea bass are showing up north of Cape Cod. 

“The Gulf of Maine is really ground zero for mitigating and adapting to climate-induced change,” Marissa McMahan, a senior fisheries scientist at Manomet, a New England science nonprofit that works on environmental issues, including by partnering with fishermen, told SeafoodSource. 

While some fishermen can adapt to migrating fish, others struggle. Large offshore trawlers that had targeted sea bass in areas like North Carolina are steaming as much as 10 hours north just to catch sea bass, McMahan said. But smaller inshore boats that use fish pots to catch sea bass can’t do that, suffering greater effects from the shifting fish.

Fishermen are responding to climate-driven species shifts in different ways. Some are targeting underutilized or undervalued species. Younger fishermen, in particular, seem more willing to look at the potential of aquaculture to diversify their income.

“That way their entire livelihood doesn’t depend on a fishery that could collapse if the species shifts,” she said. But most fisheries are closed or have limited entry, making it difficult to get a license, she added. “So if you’re a lobstermen looking to diversify into another wild harvest fishery, there are very few options.”

Manomet is helping fishermen prepare. The group has worked with soft-shell clam harvesters to develop farming techniques, and is researching the viability of quahog aquaculture. They are working on developing fisheries and markets for invasive green crab, so fishermen can benefit from them economically.

As fish migrate to new waters, better data is needed to really assess stocks. Fishermen and their observations need to be included, McMahan said.

“They are on the front lines, so to speak, and witness the changes we are talking about each and every day. The amount of knowledge they posses about these ecosystems and stocks is unparalleled,” McMahan said.

Photo courtesy of the Freezer Longline Coalition