Marine Fisheries
Title:	Examining settlement dynamics of postlarval American lobster, Homarus americanus, in Southern New England/LMA 2
Author(s):	"Kelly A Whitmore, Robert P Glenn, MA Division of Marine Fisheries
Date:	Tuesday, April 27, 2010
Time:	1:05 pm - 1:25 pm
Room:	Lexington
Abstract: The lobster stock in the Massachusetts portion of the Southern New England/Lobster Management Area 2 is in poor condition. Stock abundance as measured empirically by the MA Marine Fisheries bottom trawl survey is at all time low levels since the inception of the survey (1981). The commercial catch from 2003 to 2007 accounted for five out of the six lowest values on record. Reductions in postlarval settlement have also been observed, even during periods when spawning stock biomass was at or near time series highs. This suggests that environmental parameters may be affecting hatching, larval development and survivorship, or larval transport. Since the late 1990's, the inshore LMA 2 region has experienced a period of excessively warm summer water temperatures. This pattern has persisted for longer than any other warming trend in the region, since 1945. Since water temperature plays a vital role in many aspects of lobster life history including egg development, egg hatching, and larval development, any alteration of these processes could produce variability in the timing and geographic distribution of postlarval settlement. In 2009, we investigated possible mechanisms influencing declines in young-of-the-year survey indices by monitoring the settlement process from egg-hatch to postlarval settlement. Our objectives were to: determine the current geographic distribution of lobster settlement in LMA 2, assess how well young-of-the-year settlement surveys monitor year class strength, assess habitat suitability in nearshore waters of LMA 2 for settlement, and examine the relationship between location of egg-bearing females and larval settlement, with the goal of determining if declines in settlement are related to changes in environmental conditions. A suite of satellite-tracked drifters, postlarval settlement collectors, and air-lift sampling efforts were used to capture information on lobster larval dispersal and young-of-the-year settlement in the Rhode Island and Massachusetts portions of LMA 2. Drifter-generated tracks identified coastal current patterns and linked hatching areas to potential inshore recruitment regions. Settlement collector results confirmed low settlement throughout the region. Temperature data were coupled with settlement patterns and compared to historical regional temperature records. Results of this study will elucidate environmental factors likely influencing the decline and lack of recovery of the LMA 2 lobster fishery.
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