Biotic and Abiotic Factors influencing....
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GRANT NUMBER:  NA46FD0328           NMFS NUMBER:   93-NER-012

REPORT TITLE:  Biotic and Abiotic Factors influencing Recruitment and Subsequent Mortality of Soft-Shell Clams in Eastern and Southwestern Maine

AUTHOR:  Beal, Dr. Brian F. and Fegley, Dr. Stephen R.

PUBLISH DATE:  September 30, 1996

AVAILABLE FROM:  National Marine Fisheries Service, Northeast Region, One Blackburn Drive, Gloucester, MA 01930-2298.  PHONE: (978) 281-9267


Soft-shell clams, Mya arenaria L., have been harvested commercially from the intertidal along the Maine coast since the mid-1800s.  Historically, 45% to 65% of all clams landed in Maine are harvested in the two eastern countries (Hancock and Washington) where, because of geographic proximity to the Bay of Fundy, twice-daily 4-9 m tides expose vast expanses of clamming habitat compared to coastal regions in more southerly regions of the state.  Between 1982 and 1992, landings in the eastern region declined by 90% while, concommitally, landings in south western Maine increased by 15% over the same time interval. To better understand the factors that may have contributed to the apparent resource decline in eastern Maine, we conducted parallel manipulative experiments at six intertidal mudflats in eastern and southwestern Maine from April to November 1995 to determine biotic aspects of the dynamics of newly settled soft-shell clam populations.  At each of the twelve sites, we initiated a long-term experiment (Experiment I) to examine the interactive effects of tidal height (high vs. low) and predator exclusion netting on clam recruitment using a generalized randomized block design.  In April, at each location, 240 four-inch plastic plant pots were filled with "mason" sand and buried flush with the sediment. These 2,880 experimental units remained undisturbed for seven months when the contents of each were sieved using an 1,180 u screen.

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