Table 5. — Number of green crabs caught in the morning 

 and afternoon at Plum Island River and Lufkins Flat 

 during 1956 



OTHER FACTORS THAT INFLUENCE 

 FEEDING HABITS 



TEMPERATURE 



The food consuinptiou of the green crab may be 

 ailected by extremes in water temperature. Green 

 crabs were presumed to be influenced by advei-se 

 temperature if less than lialf of the stomaclis had 

 food ; if more than half of the stomachs with food 

 were also nearly empty; and if no other factors 

 were suspected to have prevented feeding. 



The number of crabs containing food clearly de- 

 clined in eight samples from the intertidal zone 

 (table 6) ; seven samples were collected when the 

 water temperatures were 11.5° C. and lower, and 

 the crab stomachs contained only shell fragments; 

 and one sample was collected when the water tem- 

 perature was 26° C. Two other samples were bor- 

 derline examples because slightly more than half 

 of the crabs had recently fed. If the sample on 

 August 26, 1955 is excluded, the total of 9 samples 

 included 696 crabs; 208 contained food, but of 

 these 129 (62 i^ercent) were nearly empty. Thus, 

 only 79 (38 percent) had eaten when the tempera- 

 tures were 12° C. or less. 



Eleven intertidal samples contained crabs that 

 had clearly been feeding when the water tempera- 

 tures were 9° C. or higher (table 6). The total of 

 11 samples included 619 crabs; 431 contained food, 

 and only 82 (19 percent) of these were nearly 

 empty. Therefore, 349 of the crabs (81 percent) 

 had eaten when the temiJeratures were 9° C. or 

 higher. 



T.iBLE 6. — Water temperatures and the percentage frequency 

 of occurrence of food in green crabs from the intertidal 

 zone, 1954-55 



Date 



195i 



Sept. 16 -. 



Sept. 23 -- 



Oct. 5 



Oct. 19 



Oct. 22 



Nov. 2 



Nov. 5 



Nov. 18 



Dec. 6 



Dec. 8 -.- 



Dec. 22 - 



1%S 



Jan. 12 



Jan. 27 



Feb. 16 



Apr. 18 



May 19 



July 23 



Aug. 26 



Oct. 21 - 



Oct. 21 



Nov. 23 



' No observation. 



Most crabs caught in the subtidal zone were 

 collected when the water was wann. A few excep- 

 tions indicated feeding at temperatures lower than 

 12° C. Table 7 includes the dates when the water 

 temperatures at the dredge sites were less than 

 12° C. More than 50 i>ercent of the crabs sampled 

 on or near these dates contained food and less than 

 half of the stomachs containing food were clas- 

 sified as nearly empty. These data suggested that 

 temperatures as low as 7° C. do not suppress feed- 

 ing. Activitj-, and presumably feeding as well, 

 probably ceased at some temperature below 7° C. 

 because on November 23, 1955, when the water 

 temperature was 2° C, no green crabs were caught 

 in the subtidal zone at either sampling area. 



Table 7. — Low water temperatures and the percentage fre- 

 quency of occurrence of food in green crabs from the sub- 

 tidal zone at Plum Island River and Lufkins Flat, 1964-56 



Plum Island River ° C. 



Nov. 5, 1954 9.0 



Nov. 7, 1955 10.0 



May 11, 1956 10.0 



Oct. 6, 1956... 10.0 



Oct. 19, 1956 10.0 



Nov. 15, 1956.- 7.5 



Lufkins Flat 



Apr. 18, 1955 11.5 



Oct. 21,1955 10.5 



Nov. 7, 1955 10.0 



May 11, 1956 8.0 



Oct. 20, 1956 9.5 



Nov. 5, 1956 7.0 



Percent Percent Percent Number 



FEEDING HABITS OF GREEN CRAB 



195 



