In Hot Water

Warming waters of the coast of the Northeast are decimating the Southern New England lobster industry.

by Scott Mullen

Standing on the open rear deck of a modest and well-weathered boat, Dr. Tracy Pugh watches as a mechanical winch hauls a length of rope out of the murky Atlantic. After a few seconds, the gears lift a rectangular cage from the water, and she and the boat’s two-man crew jump into action. They slide the cage over the bulwark and look inside at their catch: a small collection of what appear to be large, reddish-brown bugs with ten squirming legs, wiggling spines, and a pair of widespread claws.

While most lobsters (before they're cooked) are a ruddy brownish color, one in every two million is blue.

While most lobsters (before they’re cooked) are a ruddy brownish color, one in every two million is blue.

After Dr. Pugh gives each one a once-over, and seemingly without regard for the safety of their appendages, the deckhands reach into the trap and begins tossing the critters, American lobsters in pre-boiled form, in every direction. Many go right back into the drink, but a few stay aboard, likely destined for a white tablecloth in an upscale establishment.

By the time the first trap is empty, a second is hanging from a pulley, ready for the same treatment. While one lobsterman deals with the second trap, another fills the first with fish scraps and prepares it for another descent to the rocky seafloor. Then the process begins again, and again, until the end of the trawl.

It is a scene that repeats itself day after day on New England’s inshore waters, and has for well over 200 years. Usually, the men and women pulling the traps are after somebody’s dinner, but not Dr. Pugh. Instead, she is collecting information. She inspects each lobster that comes out of the water, measuring it, determining its sex, and recording data.

Dr. Pugh is a marine fisheries biologist with the state of Massachusetts and a representative to the American lobster technical committee of the Atlantic Marine States Fisheries Commission, the organization that monitors and regulates state fisheries on the Eastern Seaboard. Since 2002, she has led the Massachusetts effort to collect data from commercial lobster traps, which is used to help develop a picture of the health of the lobster population. Unfortunately, that picture has lately been a troubling one.

Over the course of the past two decades, the American lobster population has been buffeted like a boat on rough seas. Of the two major groups of lobsters in U.S. waters—the Gulf of Maine stock and the Southern New England stock—the latter is in dire straits. Under pressure from a changing environment, and especially warming waters that are themselves a result of global climate change, the stock has seen an unprecedented drop in numbers, from a record high of more than 50 million in the late 1990s to a current record low of less than 10 million. And it is unclear whether or not this downward trajectory will abate any time soon.

At the end of the summer of 2015, the ASMFC released a benchmark stock assessment, the first major inquiry into the state of the American lobster fishery since 2009. For two years before the assessment was published, scientists and researchers from up and down the East Coast accumulated and analyzed data, ran models, interpreted results, and tried to figure out what was going on beneath the waves from New Jersey to Maine.

What they found was a mixed bag. Overall, the lobster catch is larger than it’s ever been. In the Gulf of Maine, by far the largest part of the fishery, the estimated number of lobsters is nearly 300 million, a figure that has roughly doubled in the last 15 years. Maine’s armada of lobster boats is regularly racking up the largest landings, what fishermen call their catch, on record, and lately it seems that the stock is growing faster than ever before. A glance at a graph displaying pounds of lobster harvested from the northern stock would suggest a fishery in its prime. But that’s only half of the story.

Farther to the south, the situation is just the opposite. Following a major die-off event in 1999, the Southern New England Stock, which reaches south from Cape Cod but primarily occupies the stretch from New York to Nantucket, entered a free fall. By 2013, the last year for which data was included in the assessment, the stock had reached its lowest estimated abundance since tracking began in the late 1970s. By most indications, the stock has collapsed.

But while the stock assessment can provide clues about what is happening to the lobster population, it doesn’t tell why. It is certain that the plunge in numbers is the result of a cocktail of factors likely including pollution, pesticides in runoff, and diseases and parasites, to name a few. But there is one element that has been getting an increasing amount of attention of late: climate change and the myriad effects it brings in its wake.

Late in the summer of 1999, the lobsters of Long Island Sound began dying. Within a few months, as many as 90 percent were dead. Diver’s in some areas reported a layer of carcasses a foot deep on the bottom of the Sound. New York and Connecticut were hit particularly hard, and the turn of the century marked the last time either state recorded any notable growth in its fishery. The die-off spurred a flurry of scientific activity. Dr. Pugh and her colleagues and peers throughout the region undertook a wide array of studies to try to identify the culprit behind the unprecedented rate of mortality. When all was said and done, five years later, the evidence pointed to a parasitic amoeba known as Neoparamoeba pemaquidensis as the ultimate killer of the lobsters.

A map of changes in lobster landings throughout the fishery, as well as water temperature changes in the North Atlantic.

A map of changes in lobster catch throughout the fishery, as well as the change in water temperature in the North Atlantic.

But the amoeba’s presence in the dead animals alone didn’t seem to explain why so many died. Something else must have left the lobsters more susceptible to the effects of the parasite. The most likely answer, they determined, was high levels stress brought on adverse environmental conditions, namely elevated water temperatures. As the lobsters were exposed to water that was warmer than usual, exacerbated that year by Hurricane Floyd, which churned up the water column and raised temperatures at the bottom of the sea, they became less healthy and their immune systems became less able to cope with disease. The result: huge numbers of lobsters died and landings from the Sound decreased by as much as 99 percent in some areas.

Warming waters, like those that contributed to the 1999 die-off, are bad news for lobsters. For a creature that is essentially a giant sea bug—lobsters are arthropods like other crustaceans, insects, spiders, and scorpions—the American lobster (or Homarus americanus as it’s known in scientific circles) is surprisingly picky when it comes to the water it likes to live in. Lobsters have a Goldilocks zone, where conditions are not too hot but not too cold, of between 54 and 64 degrees Fahrenheit. Since they are cold-blooded critters whose body temperature matches the temperature of the water around them, when the water falls below that range they become lethargic, their metabolism slows, and they have trouble growing.

Temperatures in excess of 64 degrees are even worse, and when they rise above 68 degrees the lobsters experience significant stress. Like virtually all animals, lobsters must breathe oxygen, which they extract from the water using gills in much the same way as a fish. Like a human athlete, when they get hot, they have to breathe at a higher rate. To make matters worse, the amount of oxygen dissolved in seawater decreases as water temperature increases. This means that higher water temperatures require more effort for respiration, leaving less energy for other lobster activities such as finding food, molting and growing, and reproducing—all of which are essential to maintaining a healthy and robust population.

Lobster disease also seems to become more common and more severe in warmer water. In particular, a condition called epizootic shell disease, which is characterized by bacteria eating away at a lobster’s shell, affects animals in more southerly, generally warmer waters much more frequently than it does to the north. In a study published in the Journal of Shellfish Research in 2006, Dr. Pugh and Dr. Bob Glenn, her colleague at the Massachusetts Department of Marine Fisheries, observed telling relationships between water temperature and shell disease. In particular, they noted that the farther south lobsters lived and the longer they were exposed to above average temperatures, the more often they experienced shell lesions. What’s more, reproducing female lobsters were infected more often than adolescent or male animals.