Warming Waters Foreshadow “Perilous” Dependence on Lobster
by Laurie Schreiber
Rick Wahle, University of Maine School of Marine Science. From 1982 to the early aughts, GOM water temperature increased about 2 degrees F every 40 years. Since 2004, that’s ramped up 10-fold, to an increase of 2 degrees F every four years. The North Atlantic in particular has been warming at a more rapid rate than the rest of the globe’s oceans. Fishermen’s Voice photo
NORTHEAST HARBOR – Warming temperatures in the Gulf of Maine have ramped up over the past decade.
Studies show lobster distribution is moving further north, in search of cooler water. That’s a situation that could one day have dire consequences for Maine’s fishing industry, which is “perilously dependent” on this one fishery, said Rick Wahle, a research professor at the University of Maine’s School of Marine Sciences.
The fishery has reached unprecedented highs with respect to volume and value.
In 2014, Maine lobster fishermen landed over 123.6 million pounds with a record overall value of $456.9 million, according to the Department of Marine Resources. With multipliers related to support businesses and to the product’s relationship with tourism, the fishery is worth far more.
Maine’s fishing industry was once dominated by groundfish; these have been depleted over time, said Wahle.
Since about the late 1980s, the abundance of lobsters started growing,” he said. “One of the prevalent hypotheses out there is that it is the very demise of the groundfish that promoted the expansion of the lobster population” because groundfish prey on lobster larvae. “We’ve depleted many of these predators.”
That’s been good for the fishing industry. But warming sea temperatures could pose a problem, he said.
From 1982 to the early aughts, GOM water temperature increased about 2 degrees F every 40 years. Since 2004, that’s ramped up 10-fold, to an increase of 2 degrees F every four years.
The North Atlantic in particular has been warming at a more rapid rate than the rest of the globe’s oceans, said Wahle.
Two thousand twelve was the warmest year on record for the western North Atlantic, on the order of 2-3 degrees C above the average warming rate and breaking all records for warming trends.
“The Gulf of Maine was the epicenter of that,” he said.
The North Atlantic is also acidifying at a rate higher than much of the rest of the world, although the impact of changing acidification on lobster abundance is not well known, he said.
“All of this, taken together, ultimately influences the distribution of lobsters in coastal waters from the mid-Atlantic to Nova Scotia,” Wahle said.
Going back to the late 1960s and the 1970s, the center of distribution was in southern New England.
“Around 1990s, things started moving to the north and east,” he said. By the late 1990s to the present, the center of distribution has been off downeast Maine and southern Nova Scotia. Cooler sea temperatures from Penobscot Bay east, as well as the lower risk of being eaten by groundfish, are likely driving the distribution surge, he said. Studies show these coastal waters have nurseries with the highest population density in the world.
“Right now, we’re looking at some of the most productive lobster habitat on the planet in our backyard,” he said.
As a result of shifting distribution, Maine landings have gone “through the roof,” he said. For half a century, landings were stable, averaging 10 thousand metric tons per year. Landings started to take off in the 1980s and early 1990s.
At the same time, southern New England has seen a different pattern, with landings falling off dramatically.
Temperature trends play an important role in distribution shifts, he said. The Gulf of Maine represents one of the steepest north/south gradients in sea temperature on the planet. Temperatures around the Bay of Fundy don’t reach much above 50-55 degrees F. By contrast, the waters off Rhode Island are 70-degrees-plus.
The gradient crosses “the lobster comfort zone” with respect to temperature, he said. Southern New England is now on the hot side for lobsters. The southern New England experience could foreshadow the future for Maine’s fishery, he said.
“Too much above 72 degrees F, things are very uncomfortable for lobsters,” he said. “We’re seeing nurseries in coastal areas receding because those shallows get too hot for lobsters. They’re moving into deeper waters where it’s cooler.”