Warming, more acidic oceans threaten New England fisheries (audio)

Lobstermen in the Gulf of Maine have posted record harvests in recent years. But in the waters just south of Cape Cod, the situation is dramatically different. Lobster populations there crashed a decade ago and have not recovered, leaving lobstermen to face the potential closure of their fishery. In the second installment of our Cape Change series, we take a look at one of the most dramatic examples of how climate change is affecting New England’s fisheries.


Rising water temperatures are thought to be responsible for the collapse of lobster populations off the southern coast of New England.
Dick Allen was just a teenager when he dropped out of college to go lobstering with his brother-in-law nearly fifty years ago. They’d leave Westport and steam about 20 miles south to a place called Cox Ledge.
“You’d haul up a trap,” recalls Allen, “and there’d be these big lobsters that you’d have to struggle to get ‘em out of the traps.”

Over the decades, Allen watched those big lobsters disappear. By the late 80’s, he says, they were basically gone.

“It was like if you went into a town and you never saw anybody over 13 years old,” he says. “You’d say well something’s wrong here. And that’s the situation we had created in the lobster population in southern New England.”

Then, around 1998, the number of lobsters with an unsightly bacterial infection known as shell disease skyrocketed, and the population collapsed. Bob Glenn, Massachusetts’ chief lobster biologist, says shell disease is rarely fatal, so it probably didn’t cause the crash. But it does make it hard for lobstermen to sell their catch and, what’s more, it’s a symptom of a population under extreme stress. The question was what was causing the stress.

“You know, we were searching for answers: what’s causing this? Why all of a sudden?” says Glenn. “Is it a chemical? Or is it environmental? Or whatever. So we just started looking at different things.”

Over the past fifty years, average water temperatures around New England have risen between two and four degrees Fahrenheit as a result of global warming. That has many marine species on the move in search of more comfortable water temperatures. Cod, mackerel, and yes, lobster, are all on that list. But many, including Glenn, initially questioned whether such gradual warming could account for the sudden demise of lobsters in the region.
“Originally, looking at the average temperatures, I just saw that small increase in the average temperature and was like well, it doesn’t seem like that much,” Glenn says. “But when we started to really break it down, looking at how long the water exceeds certain temperatures, and that kinda really stuck out.”

Lobsters are exquisitely sensitive to water temperatures above sixty eight degrees Fahrenheit. They get stressed, become susceptible to disease, and start to move away. Around 1998, the number of days each year that water temperatures rose above that mark more than doubled, like someone had flipped a switch. Glenn is convinced that these underwater heat waves are behind the disappearance of lobsters from important spawning and nursery areas like Buzzards Bay. If he’s right, it could spell disaster for the southern New England lobster fishery.

“In 15 or 20 years I see one of two things,” says Glenn. “I see an extremely, a much smaller scaled back industry that is a fraction of what it currently is – a small number of boats fishing and making a profit on a sustainable but pretty small stock of lobsters.” That’s the optimistic scenario. “Or the worse alternative would be that maybe it’s a fishery that you see slowly phase out.”
Stony Brook University
The impacts of ocean acidification – slowed growth and thinner shells – are strikingly visible in a side-by-side comparison of quahogs raised in water simulating past (250ppm), present (390ppm) and future (750ppm) levels of atmospheric carbon dioxide.
So far, the lobster fishery south of Cape Cod is the most dramatic and clear-cut example of climate change’s affect on New England’s fisheries. But scientists expect major declines in fisheries ranging from cod to scallops, declines that could easily cost Massachusetts fishermen a hundred million dollars each year in lost revenues. And it’s not just because of rising temperatures.

“When we add carbon dioxide to the atmosphere from industrial activities like burning fossil fuels or deforestation, some of that carbon dioxide enters seawater,” explains Sarah Cooley, a research associate at Woods Hole Oceanographic Institution.

That carbon dioxide fundamentally alters the chemistry of the ocean – increasing acidity and limiting the availability of minerals that animals like corals and oysters need to build hard skeletons and shells. Cooley has been trying to pin down the likely impact of so-called ocean acidification on New England’s shellfish industries.

“At this time, we feel pretty comfortable saying that ocean acidification is very likely to be a strong stressor on certain species,” says Cooley. “And it is likely to result in some level of harvest decrease. But it’s going to be difficult to detect that, because at the same time we have ocean acidification, we have intense fishing pressure, we have a warming ocean. So it’s going to be very hard to pick out whether ocean acidification is the culprit or temperature rise, or anything like that.”

Cooley says that getting a handle on the combined impacts of fishing, pollution, and climate change is critical for the future of New England’s fisheries. But if carbon dioxide emissions continue unabated, the impacts of a warming and acidifying ocean will become increasingly obvious. The collapse of southern New England’s lobsters may well turn out to be only the tip of the iceberg.

Heather Goldstone, WCAI, 28 February 2012. Web site.

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