chemical barriers (Hanks, 1961) were used to 

 control i^redation by green crabs. These devices 

 were usually installed in an area during early 

 spring and maintained until late fall because green 

 crabs feed for G to 7 months of the year. 



The entire ijopulaition of crabs may not be feed- 

 ing actively at any one time in Plum Island Sound. 

 Few ovigerous females were cauglit by dredging, 

 but many of these samples were taken when, ac- 

 cording to Broekhuysen (1936), ovigerous females 

 would be scarce. Nevertheless, this study and un- 

 published records of green crabs caught by the 

 staff of the Bureau of Commercial Fisheries indi- 

 cated that ovigerous females were generally less 

 active than nonovigerous crabs. A total of 124 fe- 

 males and 4 males were caught in three collections 

 from the outflow of a hydraulic dredge that was 

 excavating channels in the Merrimack River basin 

 during June 1953 ; 94 percent of the females were 

 ovigerous. At the same time traps and a scallob 

 dredge fished near the area caught 24 males and 31 

 females, but only one of the females was ovigerousl. 

 Apparently ovigerous females are generally int- 

 act ive and buried in the bottom substrate where 

 the scallop dx-edge does not catch them. 



The inconsistent feeding habits of each sex in 

 the two areas sampled suggested that some aspect 

 of their behavior may also be dissimilar. Male 

 green crabs actively seek females that are about to 

 molt, as they can mate only with soft-shelled indi- 

 viduals. It is not completely known how males se- 

 lect females that are about to molt, but Broekhuy- 

 sen (1936) believed that as female crabs approach 

 ecdysis they become passive to the advances of 

 male crabs. Upon finding such a female, the male 

 picks her up and holds her upside down beneath 

 his body. The female may be carried by the male 

 for several days befoi-e the female molts and mat- 

 ing takes place. While seeking and holding a fe- 

 male, the male's search for food probably is 

 restricted. 



To obtain indirect evidence of readiness for 

 mating, I counted female green crabs in the pre- 

 molt condition (data combined for 1955 and 1956) 

 and found 4.8 percent at Plum Island River and 

 0.5 percent at Lufkins Flat. ^Males in the Plum 

 Island River area, then, may have been more ac- 

 tively seeking mates than feeding because molting 

 females were more available there. The time spent 

 seeking and holding a mate may have contributed 



to the observed differences in the feeding habits 

 between the sexes at Plum Island River. 



These observations do not contradict Dear- 

 born's ' conclusion that male and female green 

 crabs have similar food habits, because he held 

 each crab in a separate container. In the absence of 

 mates, male crabs probably had feeding habits 

 similar to *:hose of nonmolting females, and were, 

 thus, like the crabs caught at Lufkins Flat. 



Female green crabs were probably more destruc- 

 tive than males to the soft-shell clam population in 

 Plum Island Sound. At least, relatively more fe- 

 male crabs were caught at both sample areas dur- 

 ing the fall, when Smith (1955) found newly set- 

 tled jiivenile Mya abundant. An abundance of 

 small-sized food, at a period in the crab's life his- 

 tory when molting, mating, low temperatures, and 

 salinity were minor factors limiting the popula- 

 tion's feeding habits, undoubtedly contributed to 

 the decline of the clam fishery in Plum Island 

 Sound. 



SUMMARY 



1. The green crab is an omnivore, but pelecypods 

 formed a dominant part of the diet of crabs col- 

 lected from Plum Island Sound, Mass., and 

 vicinity. 



2. Green crabs exhibit raptorial feeding abili- 

 ties, aided by accessory organs which direct them 

 to sources of food. The abundance, size, and kind 

 of foods influence feeding. 



3. Pelecypods were most frequent in crabs 30 to 

 59 mm. wide even though all sizes contained essen- 

 tially the same kinds of food. 



4. The feeding habits of green crabs were regu- 

 lated by the time of day and the tides. The greater 

 frequency of food in crabs caught during low tide 

 and just after sunrise suggests that feeding is 

 heaviest at night and at high tide. 



5. Activity, and presumably feeding as well, 

 probably were restricted at water temperatures 

 below 7° C. 



6. Low salinity apparently did not influence 

 feeding. 



7. Female crabs were relatively more numerous 

 than males in the fall and, thus, were probably 

 more destructive of pelecypods in Plum Island 

 Sound. 



' Footnote 1. 



FEEDING HABITS OP GREEN CRAB 



201 



