FRIENDSHIP, ME - In mid-December, lobstermen from Friendship and Monhegan, ME and scientists from The Lobster Conservancy (TLC) already were seeing excellent returns from sonar tracking tags deployed on egg-bearing lobsters to trace their movements in Muscongus Bay, located in the midcoast area west of Penobscot Bay.

    Lobstermen had recaptured animals bearing the sonar tags and also had plotted the location of others using hydrophones, which are underwater devices that pick up the unique series of beeps emitted by each of the special tags.

    Combined, the recapture and sonar returns added up to a far greater number of lobsters accounted for than in traditional tagging studies.

    The project kicked off late last year when TLC researchers went out on lobster boats in September and October and outfitted each of 191 eggers caught with three pieces of equipment: a sonar transmitter; an identification tag; and a temperature data logger.

    The tagged lobsters were released near where they were caught, and their positions were recorded on a global positioning system.

    Although many previous tagging studies have attempted to follow eggers, most returns are reported soon after tagging. By using sonar tracking equipment, TLC is following the movements of the eggers for longer periods of time - whether or not they choose to climb into traps.

    So far, researchers were finding that many of the eggers are staying put for the winter.

	Three pieces of equipment were attached to 191 egg-bearing lobsters: a sonar transmitter, an identification tag, and a temperature data logger. (TLC photo)

    As of mid-December, project participants had relocated 103 of the tagged lobsters at least once, 36 twice, 13 three times, nine four times, two five times, and one tagged lobster six times.

    Of those, 39 were recaptured in traps once, six twice, and one three times. The rest of the relocations were made using the hydrophones.

    About half of the relocated lobsters had moved more than 1 kilometer, which is 0.62 miles. The longest point-to-point distance traveled was 11.1 miles by a lobster tagged at the end of September and recaptured in the middle of December.

    Most of the lobsters that were moving were heading in a southerly direction out of Muscongus Bay to deeper water.

    The increased success of locating lobsters using sonar tracking techniques - in terms of both number of lobsters relocated and number of times individuals have been located ­- is impressive.

	Besides recapturing the sonar-tagged lobsters, their movement can be monitored with hydrophones. Nine lobster boats were outfitted with hydrophones and the captain and crew were trained to identify lobsters and record the necessary data. Above, project scientist Diane Cowan, right, works aboard the Amanda Kate with Philip Bramhall, left, and Normand Collarmore. (TLC/Sara Ellis photo)

    The two-year Sonar Tracking Project is funded by the Northeast Consortium and the Davis Conservation Foundation and depends on collaboration between TLC and a group of lobstermen from Friendship and Monhegan.

    Participants in this study anticipate that the data collected through the project will provide baseline maps revealing habitat use by egg-bearing female lobsters and answer questions about egg production by local broodstock.

    For example, if female lobsters that mate and spawn in Muscongus Bay remain there or return there to release their young, this could provide evidence for local production.

    On the other hand, if these females leave the bay during brooding and release their eggs offshore, then this could provide evidence for remote production and larval transport.

    If it turns out that both scenarios occur, which is the most likely outcome, then both hypotheses may be valid and could help explain the continued health of Maine's lobster fishery. That is, even if there is a depletion in a local stock, the area could be replenished by larvae from remote locations.

    In addition, if the large females, which produce proportionally more eggs than smaller females, are the ones moving offshore and sending their larvae far and wide on coastal currents, this evidence could add support to Maine's practice of protecting oversized lobsters.

    More specifically, the goals of the study are to determine the following:

     - If and where female lobsters congregate when they are spawning (extruding eggs onto their tails), brooding (carrying and caring for their eggs), and hatching (releasing larvae);

     - If the behavior of first-time spawners deviates from the behavior of more experienced females; and

     - The relationship between brooding and temperature.

    Project scientists include Diane Cowan of TLC, Andy Solow of the Woods Hole Oceanographic Institution, and Win Watson of the University of New Hampshire.

    "We are testing the hypothesis that local broodstock may make major contributions to local lobster stocks by exploring the relationship between the movements of egg-bearing female lobsters and the location of larval release," said Cowan.

    Lobstermen are an integral part of the project, both by allowing their boats to be used as research platforms and actively gathering data for the study.

    The participating lobstermen have a wealth of knowledge on lobster populations and movements in the areas they fish. This project provides lobstermen an opportunity to share that knowledge with scientists and generate important baseline data about the resource on which their livelihoods depend.

    "We're out there six days a week vs. some scientists that are only out a few times a year," said Mark Wallace of the Pamela B.

    They also have a sense of ownership in the project and the results that will come out of it.

    "We're actually doing the science," said Philip Bramhall of the Amanda Kate. "We know how the data is being collected and that it's real."

    Because each sonar transmitter emits a unique series of beeps that can be heard by a hydrophone, a lobster can be individually identified from a boat up to 800 meters away.

    The 12-month life of the sonar transmitter battery allows sufficient time to follow females from spawning to hatching.

    Nine lobster boats were outfitted with hydrophones and the captain and crew were trained to identify lobsters and record the necessary data.

    These trained lobstermen "listen" for the females and report on their current location.

    The temperature data logger affixed to the female lobster records the water temperature every hour for over a year. This information will be useful in determining the range of temperatures the female lobsters and their eggs were exposed to during the brooding period.

    Lobster eggs develop faster in warmer water. During the summer, shallow water is warmer than deep water, but in the winter the reverse is true.

    Some scientists believe lobsters, especially egg-bearing females, move in response to temperature change. Brooding females are thought to move out to deep water for accelerated incubation time. The relatively large number of females tagged for this study should allow this hypothesis to be tested.

    The red identification tag (see picture page 10B) contains TLC's name and phone number and the lobster's identification number.

    Any lobsterman who hauls up a sonar-tagged egger is asked to call in and report the lobster's location, depth, and condition.

    For more information on this project, call The Lobster Conservancy at (207) 832-8224 or e-mail Diane Cowan at dcowan@lobsters.org.

    [Dan O'Grady is an Island Institute fellow who is currently working with The Lobster Conservancy.]