Green crabs in NH

Warming ocean waters have allowed the green crab population to thrive along the New Hampshire coastline.

Scientists at the University of New Hampshire are working to determine how fish and plant species are affected by warming ocean waters, and a brother and sister team in the recreational fishing industry say they are finding ways to adapt to the changes they are seeing.

According to the National Oceanic and Atmospheric Administration, over the past two decades, the Gulf of Maine has warmed faster than 99% of the global ocean. This has caused many marine species to move north, farther offshore or to change their feeding patterns.

UNH’s Nathan Furey, assistant professor of biological sciences, and Kathy Mills, research scientist at the Gulf of Maine Research Institute in Portland, Maine were awarded more than half a million dollars by the National Science Foundation this past summer to look into how warming waters and migrating fish populations are going to affect the diets of fish and the health of species in the northwest Atlantic Ocean.

Furey and his team are looking at 40 years of stomach content data to determine the historical diets of fish. They will use that information to build models which predict what species might be found in the Gulf of Maine in the years to come.

“We want to project what might happen 30 years from now,” Furey said.

Findings will be shared with the National Marine Fisheries Service’s Northeast Fisheries Science Center in Woods Hole, Mass., to help in the management of fisheries.

Researchers at UNH are also looking at the effects on the environment fish are living in.

Jennifer Dijkstra, research assistant professor at the School of Marine Science and Ocean Engineering, studies kelp forests.

Small fish rely on kelp forests for hiding from predators, but these towering blades of seaweed have been taken over in the past 35 years by lower turf-dominated seaweed species. Researchers believe these changes could impact the behavior of small fish as they have fewer places to find refuge.

Dijkstra said the problems with lower turf-dominated seaweed species have become more apparent due to marine heatwaves in the Gulf of Maine.

Despite the challenges, Dijkstra said there may be an opportunity to restore kelp forests.

“I think restoration is an option. I think discovering those areas where restoration will be successful will be very important, and also discovering what species may be better for restoration,” Dijkstra said.

Green crabs thriving

At least one marine creature is thriving due to warming waters on the coastline of New Hampshire: green crabs.

Gabriela Bradt, fisheries extension specialist for NH Sea Grant and UNH Cooperative Extension, tracks the invasive species of crab found in shallower water along the shoreline.

The population of green crabs has exploded locally in recent years due to rising ocean temperatures. Bradt said Wednesday green crabs are problematic because they prey on soft shell clams, mussels and baby oysters.

Bradt said people were still trapping green crabs locally until January.

“It’s definitely the warming waters, and because of it, the green crab population is really taking hold,” Bradt said.

“Our winters here in New England are no longer those frigid, long cold winters, although they might feel like it today.”

Green crabs can be consumed by humans and Bradt has worked on programs in the past to get local restaurant owners to use them as part of their menu options.

Adjunct Scientist Andrew Pershing of the Gulf of Maine Research Institute shared in his 2020 update on warming waters in August that since 2010, the temperature in the gulf has been above average 92% of the time, and at heatwave levels 55% of the time.

“Like so many other parts of our lives this year, what used to be unimaginable is now a new normal,” Pershing wrote.Species in growth mode

Capt. Bob Tonkin and Capt. Jeanne Bailey, who run Captain Bob’s Lobster Tours & Fishing Charters in Hampton, say they have seen an increase in Atlantic bonito and black sea bass recently.

Higher water temperatures locally have also led to an influx of menhaden, commonly called pogies.

Pogies are a popular food source for larger fish and seals. They have been eating plankton growing closer to shore due to higher water temperatures.

“The pogies are still super thick,” Tonkin said. “You could walk on them, there’s so many of them.”

Tonkin said because of the pogies, striped bass are not as hungry, so they are harder to catch during the summer months. He has pivoted to more sport fishing and family trips as a result.

Tonkin said they have seen sharks, tuna and whales closer to shore than ever before during tours.

“Right in the mouth of the river, we’re seeing whales,” Tonkin said. “It’s not something we’re accustomed to.”

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