Biotic and Abiotic Factors influencing Recruitment and
Subsequent Mortality of Soft-Shell Clams in Eastern and
Beal, Dr. Brian F. and Fegley, Dr. Stephen R.
September 30, 1996
National Marine Fisheries Service, Northeast Region, One
Blackburn Drive, Gloucester, MA 01930-2298. PHONE:
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.