CHANGES IN HERMIT-CRAB FEEDING PATTERNS IN RESPONSE TO TRAWLING DISTURBANCE

Bottom trawling leads to the death, injury or exposure of benthic faun a, thus creating a potential source of food for predators and scavenge rs. We examined the behaviour of 2 sympatric species of hermit crab, P agurus bernhardus and P. prideaux, in response to beam trawl disturban ce. Catch numbers, body size and stomach contents of the 2 species wer e analysed from a treatment wayline before and after it was fished wit h a 4 m commercial beam trawl and from 2 adjacent unfished control way lines. Catch numbers of P. bernhardus were significantly higher on the treatment wayline 2 and 3 d after fishing, whilst on the fourth day t hey were no longer significantly different. Numbers of P. prideaux did not vary significantly between control or treatment waylines or with time. After fishing, the size distribution of P. bernhardus on the tre atment wayline became skewed towards larger size-classes of crabs. For 3 d after fishing, P. bernhardus collected from the treatment wayline had significantly higher stomach content weights per unit body mass t han those from the control area. No such difference occurred for P. pr ideaux. The diets of the 2 species were similar, including crustaceans , polychaetes and molluscs, although the ranked importance of each typ e of prey differed between the 2 hermit crab species. There was an inc rease in the proportion of crustaceans and polychaetes found in the st omachs of P. bernhardus from the treatment wayline 1 d after fishing. These results suggest that P. bernhardus migrate into recently trawled areas because they are able to benefit from feeding on the damaged or disturbed fauna generated by beam trawling. P. prideaux apparently ne ither move into the trawled area nos respond to the additional food so urce if already there, even though they have similar dietary character istics to P. bernhardus.