Lobsters on a roll
New research reveals that lobsters are too smart for fishermen's traps - they're dining and going home.
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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.Skip to next paragraph
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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.