The impact of hydraulic clam dredging and storm on a soft bottom community

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The direct effect of hydraulic dredging on an ocean quahog population and accompanying fauna in shallow waters (10 m depth) was investigated by comparing samples from dredge tracks and nearby undisturbed areas. The rate of the shell breakage of ocean quahog left in the track was 21%, and these shells were on average smaller than those caught. The dredge tracks disappeared shortly after dredging and the effects on benthic fauna other than ocean quahog were of short duration, with faunal densities attaining pre-disturbance levels in a few months after dredging in most cases. In April 2006 a heavy storm caused transport of large quantities of ocean quahogs from this area, the soft bottom at 10 m depth, up onto a hard substratum at lower depth. There the clams unable to burry down again and escape were easy prey for predators. A year later only empty shells and shell fragments were observed at this site, but no living clams.