MEPS 144:63-72 (1996)  -  doi:10.3354/meps144063

Changes in hermit crab feeding patterns in response to trawling disturbance

Ramsay K, Kaiser MJ, Hughes RN

Bottom trawling leads to the death, injury or exposure of benthic fauna, thus creating a potential source of food for predators and scavengers. We examined the behaviour of 2 sympatric species of hermit crab, Pagurus bernhardus and P. prideaux, in response to beam trawl disturbance. Catch numbers, body size and stomach contents of the 2 species were analysed from a treatment wayline before and after it was fished with a 4 m commercial beam trawl and from 2 adjacent unfished control waylines. Catch numbers of P. bernhardus were significantly higher on the treatment wayline 2 and 3 d after fishing, whilst on the fourth day they 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 treatment 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 than those from the control area. No such difference occurred for P. prideaux. The diets of the 2 species were similar, including crustaceans, polychaetes and molluscs, although the ranked importance of each type of prey differed between the 2 hermit crab species. There was an increase in the proportion of crustaceans and polychaetes found in the stomachs 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 neither move into the trawled area nor respond to the additional food source if already there, even though they have similar dietary characteristics to P. bernhardus.

Hermit crabs · Feeding · Beam trawling · Fishing impact

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