Lobsters on a roll
New research reveals that lobsters are too smart for fishermen's traps - they're dining and going home.
Down on the ocean bottom, marine biologist Bob Steneck seems to be finding a lobster under just about every stone.
Mr. Steneck reveals them hiding under kelp fronds, amid fields of round rocks dumped here by ancient glaciers, and in little lobster fox holes dug into the sand.
Lobsters are everywhere, including the inside of a lobsterman's trap nearby. One drives a small crab away from the bait-filled bag hanging in the trap and resumes eating. Two others have dug burrows under the trap and wait patiently for their turn to dine.
Here lies the great lobster mystery. For nearly three decades, federal fisheries managers have warned that the lobster stock is overfished and faces imminent collapse. But instead, the annual lobster catch has exploded, from 20 million pounds in the '70s and early '80s to around 50 million pounds today, and scientists like Steneck see little evidence that fishermen are hurting the lobster population.
"Lobsters may be globally unique in that their population keeps growing despite high rates of exploitation by fishermen," says Steneck, who studies the tasty crustaceans at the University of Maine's Darling Marine Center in Walpole.
But scientists are beginning to get a handle on why lobsters are thriving in the face of the sort of overwhelming fishing pressures that have devastated cod, haddock, urchins, and other species in the northwest Atlantic.
Their discoveries are turning traditional fisheries management assumptions on their head, and appear to vindicate lobstermen's long-standing assertions that they have little effect on lobster population.
Take lobster traps themselves. Scientists and lobstermen generally assumed that the box-shaped traps were pretty effective snares. Lobsters enter the traps through a funnel-shaped opening and, after dining on bait inside, were thought to have great difficulty finding their way back out through the narrow end of the funnel.
Turns out, that's completely wrong, and University of New Hampshire zoologist Win Watson has the videotape to prove it.
Curious as to how effective traps were, Professor Watson attached an underwater video camera to a standard trap and dropped it down to the seafloor off Portsmouth, N.H. Given that hauled traps usually contain only a handful of lobsters, Watson expected the tape would show a modest number of lobsters approaching the trap.
But when Watson's team looked at the first time-lapse video, they were totally stunned by what they saw. "The numbers of lobsters were just amazing," Watson recalls, with lobsters scuffling and fighting over the trap. "It looked like an anthill."
But the biggest surprise was that the lobsters were happily wandering in and out of the traps at will. On the videos, lobsters of all sizes crawled in and out of the funnel-shaped entrance as they pleased. The biggest impediment they faced were other lobsters, which did their best to chase newcomers away from the bait. Only 6 percent of the lobsters that entered the trap failed to find their way out again. (To watch the video, go to http://zoology.unh.edu/faculty/win/lobster%20ecologyfisheries/ltv.htm.)
Lobstermen who have seen the video have been just as surprised. "It's pretty discouraging to think that here we, as intelligent human beings, have been trying our best to harvest this thing that has no brain to speak of and they're outsmarting us," says an amused Pat White of the Maine Lobstermen's Association.
"But it may be that part of the success of our fishery is due to the fact that our traps are as inefficient as they are," says Mr. White, who lobsters out of York, Maine.
Lobstermen have long argued that current conservation laws and practices really work, maintaining a healthy breeding stock. In Maine, where the lion's share of US lobsters are caught, fishermen throw both small and very large lobsters back into the ocean. Egg-bearing females are also thrown back, and are marked with a small V-shaped notch in their tails, a signal to later lobstermen that this is a breeder never to be brought to the dinner table.
Fisheries scientists used to argue that V-notching made little difference to the lobster population. But new surveys of the lobsters caught - but not necessarily kept - by Maine fishermen show that nearly two-thirds of all egg-producing females already have a V-notch, meaning they're breeding for at least the second time in their lives.
"There's an incredible number of these V-notched lobsters out there in Maine waters," says Carl Wilson, chief lobster biologist at the Maine Department of Marine Resources lab in Boothbay Harbor, which compiles the statistics. "Maybe this is something that really works."
"For years, fishermen have been asking federal [fisheries managers] to take into account the conservation activities they're engaged in," says Philip Conkling, president of the Rockland-based Island Institute, which has helped foster research collaboration between Maine scientists and lobstermen. "Now here's robust evidence that there are all these V-notched and oversized lobsters that are never taken into account" because the lobster-population models that fisheries managers used to assess the population are largely based on the lobsters fishermen land at the dock, not the ones they throw back in the water, he says.
While conservation practices may be working, other research shows that the long-term health of the lobster fishery may in fact be largely out of the lobstermen's hands. Instead, the interaction of sometimes subtle natural factors - currents, water temperature, wind direction, and bottom types - may be the most powerful influence on the size of lobster populations in the Gulf of Maine.
That's because after lobsters release their eggs, they hatch into tiny larvae that can float great distances on coastal currents before arriving at nursery grounds. Researchers are discovering that a current that flows from east to west down Maine's coast, may serve as a giant lobster superhighway, delivering numbers of larvae into Maine's lobster-crowded Penobscot Bay from as far away as Canada.
"If this proves correct, then, in the big picture, that means how this fishery gets managed by other states and countries is very important," says oceanographer Lew Incze of the Bigelow Laboratory for Ocean Sciences in Boothbay Harbor, one of the scientists studying the phenomenon.
The researchers suspect that some sort of long-term change in the path of ocean currents may explain the current explosion in lobster numbers. The coastal current presently dumps large numbers of larvae over ideal nursery habitat, vast fields of small rocks off Penobscot Bay. A slight change in the currents - due to natural cycles or global warming - might deposit commuting larvae on sand or mud bottoms where, lacking hiding places, they make a quick meal for hungry fish, according to biologist Rick Wahle, also at the Bigelow Lab.
Dr. Wahle has been finding large numbers of these baby lobsters in recent surveys. But because lobsters don't grow at an even rate, scientists still can't say how this will effect the fishery in five to seven years, when the babies begin to reach legal size. "We're hoping this decade will be the one where we start being able to make these kinds of predictions," he says.