Impact of green crab (Carcinus maenas L.) predation on a population of soft-shell clams (Mya arenaria L.) in the Southern Gulf of St. Lawrence

摘要

A caging experiment was carried out on an estuarine mudflat in Pomquet Harbour, Nova Scotia, Canada from late May to early September 2001. Six replicate 0.83 m(2) cages were set up for each of the following treatments: low predator density cages with one green crab (Carcinus maenas), high predator density with five green crabs, exclosure cages with no crabs, and control cages with sections of the sides removed. In addition, six 0.83 m(2) sections of exposed mudflat served as further controls. Green crabs significantly reduced numbers of small (<17 mm) soft-shell clams (Mya arenaria), removing ca. 80% of the small clams within low and high predator cages. There was no significant difference in large (>17 mm) soft-shell clam densities for any of the treatments. Green crabs consumed small clams at a minimum rate of 3.1 clams/crab/day and a maximum rate of 21.8/clams/crab/day. Predation intensity did not vary with density of crabs within cages. [References: 35]