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by Rebecca Clauss
DURHAM, NH - Several years ago, Marc Palombo, a Sandwich, MA-based fisherman and a member of the Atlantic Offshore Lobstermen's Association, picked up the phone to try to find the answer to a question that had been puzzling him: "Why are my lobster catches in this region so low?"
Eventually, he was directed to Jim Manning, a scientist at the National Marine Fisheries Service's Northeast Fisheries Science Center. As it turns out, Manning and Palombo had similar interests for different reasons.
Manning's focus was the physical oceanography of the Gulf of Maine and Georges Bank, while Palombo was curious how the physical environment affects lobsters where he fishes offshore.
After talking, Manning sent Palombo a temperature probe that he could attach to his lobster trap and leave on for months to record data. This was the start of the collaborative project "Environmental Monitors on Lobster Traps (EMOLT)."
With funding from the Northeast Consortium, the EMOLT project began in earnest in November 2000. It involves partners from the leading lobster organizations: Atlantic Offshore, Massachusetts, Maine, and Downeast Lobstermen's associations.
David McCarron, director of the Gulf of Maine Lobster Foundation, is responsible for coordinating much of the effort by training participants and assisting in data collection.
Temperature shifts
The underlying goal of the first phase of the project is to better understand the incidence and extent of temperature shifts in the Gulf of Maine and on Georges Bank and to observe what type of effect these shifts may have on migratory lobster populations in the area.
Approximately 50 temperature probes are now operational on lobster traps set out along the New England coast from the inshore waters of Downeast Maine to the southern flank of Georges Bank.
Preliminary data from Phase I readings show that bottom water temperature was especially cold off Georges Bank this spring.
Arthur Sawyer, vice president of the Massachusetts Lobstermen's Association who fishes out of Gloucester, has had one temperature probe on a lobster trap during the first phase of the project and that has recorded some interesting temperature data.
While located approximately 60 fathoms below the surface, Sawyer's probe detected a 3°-4° F drop during a storm, which occurred in early March.
According to many lobstermen, this year's lobster hauls have been notably low.
"Right now, some friends of mine are crying the blues," said Sawyer.
Like many lobstermen, Sawyer feels that low lobster catches are linked to cold bottom water temperatures.
Salinity questions
EMOLT supporter Bill Adler, executive director of the Massachusetts Lobstermen's Association, and participant Palombo have found that results from the first phase raised even more questions about the significance of salinity in lobster abundance and migration.
In phase two of the project, salinity probes will be added to some of the lobster traps.
Salinity, although slightly more difficult and expensive to measure, is a much more effective tracer of freshwater intrusions, such as runoff due to melting snow and ice, heavy spring rains, and input from remote source waters.
Findings from earlier studies have shown that lobsters in estuaries become stressed under low-salinity conditions and will migrate to deeper, saltier water in response to stormy weather (Jury et al., 1995; Jury et al., 1994). Whether these conclusions apply to the saltier environment outside the estuaries is still uncertain.
Initially, the primary focus of the project was on episodic or sporadic events, such as Gulf Stream rings, periods of upwelling or downwelling, storm events, and how they might impact lobster migration.
But the project participants may be changing their focus.
"Episodic events may be less important in controlling the lobster population in the long run," Manning said.
During a particularly cold season, such as this year's, "lobsters are more sluggish and likely to burrow, which may impact seasonal migration," he explained.
Project participants are now moving toward a year-to-year way of thinking. By concentrating more on year-to-year changes, the participants observe larger signals and can, in turn, draw better conclusions concerning lobster movement and bottom water variability.
Big picture
By measuring bottom water temperature and salinity in the coastal region of New England at fixed locations over multiple years, EMOLT participants may be able to determine whether longer-term processes, such as climate change, have more of an impact on lobster movement than smaller-scale events.
In addition to studying the impacts of environmental factors on lobster populations, another major objective is to determine whether changes in temperature and salinity are related to local processes, such as river input and heating at the surface, or more remote inputs, such as ice melt from the north.
In the future, this knowledge could be used to predict water mass movement and thus lobster migration.
The major sentiment shared by most of the participants is that EMOLT is a positive experience for building trust among scientists and fishermen.
"You have to produce science that everyone can agree on," Adler said. "Unlike groundfish, where everyone agreed the numbers were declining, scientists said that lobsters would collapse ... which wasn't true. (Later on) the scientists told us, 'Maybe we were wrong.'"
McCarron expects to receive eight salinity probes in the near future and will conduct a training session for participating lobstermen after the initial testing of these probes. The salinity monitors will be deployed along the coast to examine the nearshore environment.
For more information on the EMOLT project, contact: Manning at (508) 495-2211 or, by e-mail, at jmanning@whsun1.wh.whoi.edu; or McCarron at (207) 363-8008 or, by e-mail, at gomlf@gwi.net.
Rebecca Clauss is the project coordinator for the Northeast Consortium.
