Hot water for fisheries management

As climate change deepens, we’ll need to understand entirely new marine ecosystems.

Here’s the good news: Since 1990, the catch of Maine lobsters has quintupled.

Okay, the rest of the news, as in other stories about climate change, is not so good.

The bumper crops of lobsters apparently have been driven by warming in the Gulf of Maine. Sea surface temperatures have climbed about four times as much in recent decades in the Gulf as in the global ocean average, according to Andrew Pershing, chief scientific officer at the Gulf of Maine Research Institute.

Lobster populations have moved northeast from southern New England waters,  Pershing said, speaking at a Metcalf Institute seminar on climate change held in Cambridge last Saturday. The shift has been a boon for Maine but a bust for fisheries south of Cape Cod.

Warmer water in the Gulf also has knocked down populations of other marine life, including some we eat (or once ate) such as northern shrimp and cod.

For hundreds of years, cod in the northwest Atlantic was one of the world’s richest fisheries. Back in the 1970s, my older brother took a trip to Georges Bank as a whale watcher on a giant Russian factory ship. At night, the sea looked like a city, dotted with the lights of dozens of fishing vessels busily sucking up cod and everything else on the seafloor.

Cod never recovered. The U.S. soon took control of our waters out 200 miles and managed the seafood take as well as it could. But most of the cod we eat now comes from China or Iceland.

Today climate change is delivering not just disruptions in ocean temperature and circulation patterns but acidification, extreme storms, loss of mangroves and marshes… As fisheries are disrupted around the world, the familiar difficulties of managing them get worse.

We don’t really know how to model newly emerging marine ecosystems, Tatiana Rynearson of the University of Rhode Island remarked at the Metcalf session. We lack the years of data needed to understand the fluctuations in conditions and populations, as Jorge García Molinos and colleagues pointed out in a 2015 paper.

Our need for long-term ocean monitoring and related research couldn’t be clearer, but climate change research is under heavy attack in the U.S.

Fortunately, compared to most of the waters of the world, we do have good historical information on Gulf of Maine waters and seafood. And while lobsters are a luxury food, they offer a positive example for management.

Unlike the case in some other states, Maine fishers must toss back lobsters that are too big as well as too small. Simulations have shown that saving the big ones has helped the shellfish survive the fishing onslaught in the Gulf, where 90% of legal-size lobsters are caught each year, Pershing said.

The saga of Maine lobsters, of course, rolls on. The catch dropped significantly in the last two years, and the highest landings keep moving north.

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