Monitoring the Offshore Fishery

The effective long-term management of the lobster fishery requires a thorough understanding of the resource and the impact the fishery has on that resource. It is generally accepted that cooperative efforts involving members of the industry, biologists and managers are likely to have the most success both collecting the appropriate data and developing management strategies that are appropriate and acceptable to all parties concerned. The overall goal of this project was to develop a monitoring program for the offshore lobster fishery so that data were collected that would assist the development of management practices appropriate to that fishery. Most data was collected directly by members of the industry, from experimental traps integrated into strings of commercial traps. Data from lobsters was entered into electronic spreadsheets, along with the GPS coordinates of the study site and bottom temperature data downloaded from temperature sensors attached to one of the experimental traps. These data were automatically transferred to us via email and used to assess the: 1) size frequency composition of catch from offshore vessels; 2) temporal and spatial patterns of abundance of all lobsters, especially berried females; 3) temporal and spatial patterns of shell disease and; 4) the relationship between the distribution of lobsters and bottom temperature. In addition, a range of sizes of female lobsters were examined from different areas of the fishery to determine the size when 50% of them reach sexual maturity and if this is correlated with water temperature. All these data are being used to improve our current management practices and thus ensure the maintenance of a sustainable offshore lobster fishery for years to come.

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Hypotheses & Objectives

Hypotheses:
The size frequency distribution of offshore lobsters captured in traps is different from inshore lobsters, with more large lobsters and fewer small lobsters.

Catch per unit effort will be correlated with water temperature, with greatest catch occurring in areas around 16C, which is the preferred temperature of the American lobster.

The sex ratio of certain areas offshore will not be 1:1 because of aggregation of reproductive females in some locations.

Berried females will exhibit a seasonal abundance, with egg stages suggesting an inshore migration to allow eggs to be released closer to shore.

Shell disease will be more severe and prevalent in the most southern study sites and may show some tendency to move north during the course of the project.

The size at maturity of female lobsters will differ according to bottom temperature, with lobsters reaching sexual maturity at smaller size classes in more southern warmer waters.

Objectives:
The overall goal of this project was to develop a monitoring program for the offshore lobster fishery, which would cover an area extending from waters off the Gulf of Maine to Hudson Canyon. The protocol and methodology outlined below were developed so that we could test the aforementioned hypotheses. The specific scientific goals of this project were to:

Determine the size frequency distribution of lobsters caught in offshore lobster traps.

Map the distribution and abundance of berried females captured offshore.

Map the temporal and spatial patterns of shell disease in lobsters captured offshore.

Measure the size at maturity of female lobsters captured offshore and determine if there is a spatial pattern that is correlated with water temperature.

Make management recommendations at the end of the study, based upon the data obtained.

The Study Site

The American lobster, Homarus americanus, is the most commercially valuable species harvested in the northwest Atlantic Ocean. It inhabits a large region extending from Labrador to Cape Hatteras, North Carolina and is found in depths of up to 700 meters. The fishery for lobsters is divided into an inshore and an offshore component for which different management regulations apply. The offshore fishery is defined by the area over 19km from shore and out to the continental shelf edge and slope. While a large amount of data has been collected from the inshore fishery, data from the offshore fishery are sparse, partly because it has a shorter history of exploitation and sea sampling offshore is more difficult due to longer times at sea. Although the offshore fishery developed in the 1950's, fishing pressure did not begin to rapidly increase until the 1960's. Landings reached a peak in 1972 and then declined until the 1980s when catch levels became more stable (Fogarty et al., 1982). Landings from the offshore fishery currently comprise 7-12% of the total catch for New England (Bob Ross, NMFS). Because of the increase in fishing pressure by the offshore fishery it has become more important to monitor the affects of fishing mortality on the offshore lobster population. Fogarty, M.J. Cooper, R.A. Uzmann,, J.R., and Burns, T. 1982. Assessment of the USA offshore American Lobster (Homarus americanus) fishery. Int. Counc. Explor. Sea Res. Doc. C.M. 1982/K: 14, 1-21. Click images to enlarge.

Management Area 3 represents the offshore fishery.
EEZ = Exclusive Economic Zone.
Management Area 3 represents the offshore fishery. EEZ = Exclusive Economic Zone.
We have established 4 areas for this study. On the map to the left these are delineated. Putative ishore/offshore migratory routes are connected by solid lines. Only sparse data are available for the GOM, so we have added a question mark.
GOM=Gulf of Maine
GB=Georges Bank (North)
VC=Veatch Canyon (Middle)
HC=Hudson Canyon (South)
50fm=50 fathom line
We have established 4 areas for this study. On the map to the left these are delineated. Putative ishore/offshore migratory routes are connected by solid lines. Only sparse data are available for the GOM, so we have added a question mark. GOM=Gulf of Maine GB=Georges Bank (North) VC=Veatch Canyon (Middle) HC=Hudson Canyon (South) 50fm=50 fathom line

Sites where Data are being Collected:
Right is a map of where our data comes from (click to expand). Approximately 12 boats participated. They each reported their catch from one string that they haul every approximately every two weeks throughout the year.

PINK circles indicate Gulf of Maine basin and inshore areas, ORANGE circles indicate Northern shoal and canyon areas, GREEN circles indicate Middle shoal and canyon areas, and YELLOW circles indicate Southern shoal and canyon areas.
PINK circles indicate Gulf of Maine basin and inshore areas, ORANGE circles indicate Northern shoal and canyon areas, GREEN circles indicate Middle shoal and canyon areas, and YELLOW circles indicate Southern shoal and canyon areas.

Recent Findings

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