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 Local news and information from Deer Isle, Isle au Haut and Stonington, Maine. |
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News Feature
by Rich Hewitt Lobsters move. Everyone knows that. But Jason Goldstein, a PhD candidate at the University of New Hampshire, wants to know why. That’s been the focus of a series of studies he’s done at UNH and he talked about his findings last week at the Winter Speakers Series sponsored by Penobscot East Resource Center. Much of Goldstein’s work has been done in New Hampshire waters and has focused on the movements of “eggers,” the egg-bearing females. Eggers, he said, carry the eggs for a 9 to 11 month period. The eggs are held under the tail during that time, and, according to Goldstein, the females are very attentive to the eggs, fanning them regularly with the flat of the tail. The eggs hatch as larvae and go through four stages of development before they settle to the bottom as juvenile lobsters. “Temperature drives almost all of those processes,” Goldstein said. “The [water] temperature impacts where they mature and also impacts egg development. As the water gets warmer, they get more active and that impacts their patterns of movement and behavior.” Some of the studies he’s done have shown that lobsters are fairly active, more active than you might think, even during the day. They tend to stay in one spot, but can move great distances on occasion. One lobster, released at the mouth of the Piscataqua River between Maine and New Hampshire, traveled as far as Cape Cod Bay, he said. In one study, they tracked 50 lobsters released at the Piscataqua River. That study showed there was much more movement among the females—both eggers and non-eggers—than among the males. The lobsters tended to travel between 1 and 5 km. from where they were released. One event that seemed to trigger movement was the hatching process. “A lot of eggers, after hatching, they took off like a bat out of hell,” he said. “They’d go several kilometers in a week. We don’t really know why that is.” Studies showed that eggs are sensitive to temperature spikes in-shore. As soon as the temperature spikes, he said, they hatch. They don’t see that off-shore, where the temperatures are more stable. He stressed that the studies he’s done have been south of Stonington and that local conditions—such as water temperature—could have different impacts on the local lobsters. The lobsters seem to like to stay put in one area and move only when there is some type of change. Temperature is one factor, but Goldstein said that a disruption to their habitat by weather also seems to be a trigger for movement. “It could be that if the habitat is good enough, with plenty of shelter and food, that they don’t want to leave,” he said. “[Moving] is a big cost physiologically to the body.” But their studies showed that rough weather does trigger movement. One inshore site they studied was hit with a northeaster, which set off the lobsters in the area. “They got up and went and didn’t stop for two days,” he said. At another site, about 80 percent of the lobsters relocated after a strong storm came through the area. It may be that fall storms in October through December contribute to the seasonal movement of lobsters off-shore, Goldstein said. “If the conditions get bad enough, they leave,” he said. “It’s always the same story.” Part of the reason for studying movements, Goldstein said, is to try to be able to predict where lobsters will hatch and where they move to after they hatch. Immediately after hatching, they do have some ability to move in the water column, but the larvae’s movements are generally directed by the currents, especially in the first few weeks. In a drift study, they tracked drift buoys that were released at the mouth of the Piscataqua River. Although the current initially took the buoys down the New Hampshire coast, it eventually swung them eastward toward the Isles of Shoals. Some of them drifted as far as the Grand Banks. The conclusion is that lobsters hatched in one area are not likely to be caught in that area, he said. Goldstein aroused the interest of lobstermen in the audience when he said that the vented traps they use are not all that effective. “They’re not that good at catching lobster,” he said. “The guys who use them are good at it, but the traps are not that efficient.” Goldstein uses traps to assess lobster populations on the bottom and said that, for research purposes, the ventless traps are much more efficient, and give a much more accurate picture of the lobsters in the area. Using a camera positioned over a vented trap, Goldstein studied the movements in and out. Other critters, such as crabs and fish, often enter and eat the bait. Most of the lobsters that approach the trap don’t enter it, he said, and most who enter it don’t get caught. At one site, which they monitored with an underwater camera, they noted that 96 percent of the lobsters that approached the trap never entered it and only 6 percent of the lobsters that entered the trap were caught. That information prompted one fisherman to ask, “How do we catch the other 96 percent?” Goldstein responded that they might be glad that they don’t catch them. In ventless traps, he said, the lobsters that get caught tear each other apart. Furthermore, with vented traps, he said, “you’re saving some for the future.” In response to questions about climate change, he said that it is difficult to tell what might happen. The predicted trend, he said, is for warmer water. If polar ice continues to melt, that would change the salinity of the ocean which, in turn, would cause changes in currents. Some predict that storms will increase and that there will be more precipitation as a result of global climate change, Goldstein said. “If that happens, what are the lobsters going to do?” he said. “There could be short-term changes or there could be long-term, adaptive changes. It’s safe to say that changes will happen over time. It’s hard to predict what they will be.” The next talk in PERC’s Winter Speakers Series will be Wednesday, January 25, from 5 to 7 p.m. Ann Backus from the Harvard School of Public Health will speak on “Working with Toxic Materials.” |
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