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The Effects of Temperature and Predators on the Abundance of the Soft‐Shell Clam, Mya Arenaria, in New England
Author(s) -
Glude John B.
Publication year - 1955
Publication title -
transactions of the american fisheries society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.696
H-Index - 86
eISSN - 1548-8659
pISSN - 0002-8487
DOI - 10.1577/1548-8659(1954)84[13:teotap]2.0.co;2
Subject(s) - fishery , abundance (ecology) , biology , predation , population , fishing , ecology , range (aeronautics) , predator , shellfish , fish <actinopterygii> , aquatic animal , materials science , composite material , demography , sociology
Explanation of the recent decrease in production of the soft‐shell clam in New England is the objective of the Fish and Wildlife Service Clam Investigations. Experimental clam farms failed unless protected from green crabs, Carcinides maenas. Laboratory experiments proved that Carcinides is a serious predator. Clam abundance decreased 50 percent in 4 years in study areas even though fishing intensity was very low and reproduction was adequate. Population decrease occurred principally in places where green crabs had become abundant, and in size groups which are attacked by crabs. Clam population on commercial flats decreased from 1949 to 1954 and recent year classes are scarce or absent. Green crabs became abundant during this period. Scientific records and interviews of fishermen indicate a northeastward extension of the range of the green crab since 1940 and great increase in abundance in Massachusetts, New Hampshire, and Maine. This extension was accompanied by decrease in clam production. An increase in the abundance of green crab in the northern part of its present range is correlated with the current warm cycle. Winter temperatures are important to survival of green crabs since they and their eggs are reported to be killed by a combination of low temperature and low salinity. Warm winters allow more crabs to survive. Predation was accepted as the principal reason for the decrease in soft clams in Massachusetts and Maine. The future of the soft clam industry depends on the temperature cycle or on development of measures for controlling green crabs.