Marine Fisheries
Title:	Could a contraction in lobster (Homarus americanus) habitat be further exacerbating poor stock conditions in the Buzzards Bay area fishery?
Author(s):	Tracy L. Pugh and Robert P. Glenn, Massachusetts Division of Marine Fisheries
Date:	Tuesday, April 27, 2010
Time:	1:25 pm - 1:45 pm
Room:	Lexington
Abstract: The lobster stock in the Massachusetts portion of Area 2 is in poor condition, with high fishing mortality rates (ASMFC 2009, 2006), low landings, low abundance, and low YOY densities (MADMF unpub data). There has been substantial attrition in the local lobster fleet, and the remainder of the fleet has shifted effort further offshore to deeper waters. This shift in effort limited the ability of MADMF to monitor the inshore portion of the stock. A cooperative ventless lobster trap survey in Buzzards Bay and Vineyard Sound was designed to reinstate broad scale sampling throughout the inshore region, and to generate robust estimates of lobster relative abundance and distribution. Sixty sampling stations were randomly selected in four depth strata, distributed proportionately to the area each strata comprised. These stations were then sampled twice monthly from May through November from 2005 through 2007 using a six-trap trawl that alternated vented and non-vented traps. Catch per unit effort and biological information for every lobster in each trap were collected. A total of 2,190 trap hauls were sampled during the 3 years of the survey, providing observations on over 41,000 lobsters. The average catches per unit effort (CPUE's) for both sublegal and legal-sized lobsters were higher in deeper strata throughout the survey period. The average catch per trawl of egg-bearing females also generally increased with increasing depth. Depth, and subsequently water temperature, appeared to be the primary factors behind much of the observed patterns in lobster catch in this study. Much of the upper part of Buzzards Bay experiences extremely warm summer water temperatures, often in excess of 20°C for long periods of time. These extremely warm summer temperatures may explain the low catch rates observed throughout much of Buzzards Bay in this survey, and may be a contributing factor to the decline of the resource in the region. Lobsters may be leaving the shallower areas to seek out deeper, cooler waters. The lobsters in our study area appear to be concentrated near the mouth of Buzzards Bay and Vineyard Sound, where deeper waters penetrate into the embayment. The catch trends indicated that large portions of the Bay with shallow depths were not preferred habitat. Data from the ventless survey, coupled with the loss of a commercially viable fishery in the upper Bay and trends observed in long-term water temperature data, suggest that the resource has experienced a change in distribution coincident with the overall decline. If the lobster resource is concentrating into pockets of deeper water as a function of habitat preference, the fleet may be able to increase its efficiency by targeting these pockets. With the resource in such poor condition, the consequences of increased fishing efficiency may be a serious detriment to the longevity of the resource and should be taken into consideration by managers.
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