Designing and Testing an American Lobster Juvenile Collector that is Suitable for Use by Offshore Vessels
Modified Lobster Traps Improve Understanding of Offshore Lobster Fishery, Management NeedsIn order to learn more about the New England and Mid-Atlantic offshore lobster fishery, scientists want to formalize the anecdotal presence of juveniles in federal waters — specifically in the Lobster Conservation Management Area 3. Using NHSG development funds, researchers tested eight different gears in 2012 designed to capture juvenile lobsters (30-50 mm carapace length) while excluding larger lobsters and other species in the offshore environment. Lobsters captured that have a carapace length less than 50 mm would serve as indicators that settlement is taking place offshore, as they are too small to have migrated from inshore waters. A few of the modified traps were relatively successful in catching juvenile lobsters, although further modifications in trap designs and site placement are necessary. The results from this research were presented to scientists at a stock assessment data meeting held in early 2013, and they will improve scientists’ understanding of the offshore lobster fishery and management needs and may help to discover new lobster nursery grounds as well. Moving forward, lobstermen will continue documenting small juvenile lobster presence in both the near shore and offshore environments.
Modified Lobster Traps Improve Understanding of Offshore Lobster Fishery, Management Needs
The goal of this project is to design modified lobster traps/collectors that can attract and retain young lobsters and be suitable for use in depths of over 100 fathoms. Once an effective tool is designed, it will be used in future studies to survey small juvenile lobsters (30-50 mm carapace length) in offshore waters.
Despite numerous investigations over the past 40 years, it remains unclear how, and if, inshore and offshore populations mix. Tagging and tracking studies find seasonal movements of lobsters between and amongst offshore and inshore areas (Cooper and Uzmann, 1971; Watson, 2008); however movements of egg bearing lobsters appear limited (Saila and Flowers, 1968). Genetic studies do not paint a clear picture of inshore/offshore connections (Harding et al, 1997; Kenchington et al., 2009; Atema, 2010); yet morphometric investigations find clear distinctions between populations (Cadrin, 1995; Atema, 2010). In particular, while there is a general consensus about the life history of inshore lobsters and the patterns of larval dispersal and settlement, it is not clear what happens to the larvae that hatch in offshore waters. Do they settle in these very deep canyons or the shallower adjacent continental shelf, or are they transported into much shallower inshore waters? Or, do females carrying eggs move inshore to release their larvae, so no settlement occurs offshore? The answers to these questions are vital to reaching a full understanding of the dynamics of lobster populations in the offshore Gulf of Maine and Southern New England waters.
While much work has been done developing an index of post-larval lobster settlement in coastal waters (e.g. the State funded New England Lobster Settlement Index), the techniques used inshore are less feasible in the deep waters of the offshore environment. To date, deployment of settlement trays offshore have been limited in scope and depths sampled (Wahle, 2009). For this reason the full range of habitats where lobsters settle remain largely unknown. Behavioral studies and near shore sampling suggests that certain aspects of lobster settlement are related to the thermocline (Boudreau et al., 1992; Wahle, 2010), with young lobsters avoiding colder temperatures. However, these findings do not preclude settlement offshore, particularly in Southern New England, where warm water extends much deeper than in the Gulf of Maine and into shallow areas like George’s Bank.
Ten years ago we received funding from the Northeast Consortium (“An automated, comprehensive monitoring program for the Atlantic Offshore Lobster Fishery”, 2001) to establish an offshore monitoring program. Our work was very successful and has been continued by the Atlantic Offshore Lobstermen’s Association (AOLA). During the course of that program we used two juvenile collectors, both based on ventless traps designed by scientists in Massachusetts. Unfortunately, in both trials the traps were found unsuitable, as they filled up with crabs and eels before fishing any lobsters. Dr. Richard Wahle had done some work offshore (in association with AOLA vessels) with his settlement trays, and admits that they are not designed for the greater depths associated with offshore lobster habitats or for hauling with offshore winches. Our goal is to work with members of AOLA to build and test new trap/collectors, designed specifically for use in offshore waters. When we achieve an appropriate design, we hope in the future to incorporate it into the monitoring program currently in progress by AOLA members.
The time is ripe for this research. The Atlantic States Marine Fisheries Commission’s past two American lobster stock assessments have been devoid of any significant data on the offshore lobster resource. Further, population declines in near shore waters, especially in Southern New England, increase the need for good quality data on inshore/offshore population dynamics. Once we have a proper gear designed we will be able to rigorously survey the population of juvenile lobsters offshore and thus provide the kind of data necessary to appropriately manage this vital resource.
The objective of this project is to design and build a collector that can successfully attract and retain small juvenile lobsters in the offshore environment. These lobsters will serve as indicators that settlement is taking place offshore because lobsters of this size are too small to have migrated from inshore waters (R. Wahle and C. Wilson, personal communications), and yet they are large enough to be active foragers and thus enter our modified trap/collectors. The collectors we design will also need to be able to stand up to the rigors of the offshore environment and the powerful hydraulic winching system used to haul offshore lobster gear. Ideally, this gear will be incorporated into a trawl of standard traps and be sampled during normal fishing activities, at depths of up to 180 fathoms. Work has already begun to develop a committee of industry members and trap builders to discuss initial ideas for gear designs. Ideas include: smaller mesh (to retain small lobsters), smaller entrance heads (to keep larger lobsters out), and the inclusion of shelter material in the trap (to enhance retention). Once traps are built, participating fishermen will deploy the gear in various areas of the offshore fishery. Each fisherman working with the experimental gear will report weekly to the project manager various metrics on each gear’s performance. Dr. Watson will deploy the same traps in inshore areas to confirm they are capable of capturing juvenile lobsters. Inshore deployments will include cameras on the gear to give us the best sense of lobster interactions with each gear type, in case modifications are required. Note: The researchers plan to also apply for funds from the Northeast Consortium to extend camera work to offshore waters.
AOLA fishermen are veteran data collectors with much collaborative research experience; they are spearheading this effort. Dr. Watson has extensive experience studying trap dynamics (i.e. Lobster TV; Jury et al., 2001). Both AOLA and Dr. Watson have experience working with the National Marine Fisheries Service to acquire the appropriate exempted fishing permit (EFP) to allow industry members to test modified gear. AOLA has already alerted the Northeast Regional Office to a potential EFP request.
This project will provide the gear necessary to effectively survey juvenile lobsters offshore. With the proper tool in place, extensive sampling can be conducted to evaluate the extent of juvenile lobsters present, and by proxy post larval settlement, in offshore waters throughout the geographic range of the American lobster. When we achieve an appropriate design, we hope in the future to incorporate it into the current AOLA monitoring program. Data from this survey is provided directly to the ASMFC lobster technical committee for use in stock assessment. Currently, stock assessment models operate with a dearth of information and are therefore forced to make assumptions about recruitment in the offshore fishery. If this project is successful, sampling will provide data to better model the interconnectedness of populations, better predict lobster production thorough their range, and most importantly, better manage the fishery to allow for continued, sustainable fishing of the American lobster resource. The discovery of 30-50 mm carapace length juvenile lobsters in offshore would be a monumental breakthrough, since it is unexpected that lobsters of this size range can survive in the offshore environment.