ROPES: FOOD HABITS OF FIVE CRAB SPECIES 



were almost equally carnivorous and herbivorous 

 (Table 3). Relatively soft-shelled, small crustaceans 

 (61%) and algae (67%) were found in the stomachs 

 of green crabs; while only 2% of hard-shelled foods, 

 such as pelecj'pods and crabs, were found. The mat 

 of algae that entangled the crabs probably provided 

 the foods seen in the stomachs and shelter from 

 large predatory crabs and fishes. Ropes (1968) 

 observed finger-sized holes, mats of algae, and Spar- 

 tina high on the marsh banks of Plum Island Sound 

 that were a refuge for small green crabs. This may 

 be a means of circumventing cannibalism, because 

 large green crabs typically occurred on the lower 

 level clam flats during high tide and migrated to the 

 subtidal zone during low tide. Ropes (1968) also 

 found that soft foods, such as Spartina and algae, 

 were important dietary components of small crabs. 

 The omnivorous food habit and existence of small 

 crabs in ecological niches apart from large predators 

 has probable survival value. 



Stomach analyses of the five crab species indicate 

 that their food habits have probable important im- 

 pact on the macrobenthic fauna of Pettaquamscutt 

 River; these results support similar findings of other 

 investigators of the food habits of crabs. The omniv- 

 orous food habit of the crabs has survival value, 

 minimizing their dependency on particular food 

 items. The carnivorous habit of blue, green, and lady 

 crabs, which have a tendency to include many small 

 pelecypods in their diet, suggests that recently 

 settled pelecypods may be rapidly eliminated or 

 severely reduced in numbers by predation. Clearly, 

 a management scheme that minimizes the effects 

 of crab predation on a bivalve fishery has a better 

 potential for success. 



ACKNOWLEDGMENTS 



I am indebted to helpful review of the manu- 

 script by Mark L. Botton, Fordham University, 

 N.Y. and Ray E. Bowman and William L. Michaels 

 of the Northeast Fisheries Center Woods Hole 

 Laboratory, National Marine Fisheries Service, 

 NOAA. 



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203 



