Stillwell and Kohler: Food habits of Carcharhinus plumbeus off U.S. northeast coast 



145 



A measure of stomach fullness was determined by 

 calculating the ratios of food volume to maximum liq- 

 uid capacity. The mean food volume ( 144 mL) was 5.5% 

 of the mean maximum capacity. Dividing the sample 

 by size-class showed that the percent stomach fullness 

 was 5.2 and 13.5 for adults and juveniles, respectively. 

 One stomach from a juvenile female was filled to 50.0% 

 capacity, while two others approximated 40.0%. Just 

 over half (53.0%) of the stomachs contained less than 

 10.0%. All adults had less than 10.0%, except for two 

 that ranged from 15.0 to 19.0%. 



Chincoteague Bay sample 



The Chincoteague sample was composed of pups and 

 young juvenile sandbar sharks captured at six fishing 

 stations located in the lower bay estuaries. The overall 

 mean fork length and body weight for these sharks 

 was 55 cm and 1.72 kg, respectively. The mean for 65 

 newborn pups (39 males, 26 females) was 50.7cm and 

 1.38 kg, while the mean for 29 (16 males, 13 females) 

 "older" pups and small juveniles was 63.7 cm and 

 2.48 kg. There was no difference in mean fork length 

 or body weight between the sexes within each size- 

 class. 



Food analysis Food items consisted of crustaceans 

 and fish. By frequency of occurrence, these contrib- 

 uted 82.0 and 13.8%, respectively. Crustaceans were 

 represented primarily by soft blue crabs (75.5%), with 

 the remainder (6.3% ) consisting of lady crabs and man- 

 tis shrimp. Fish prey consisted of small flounder, an- 

 chovy, Atlantic silver sides, mullet, and one smooth 

 dogfish (48cmTL) eaten in three pieces. A more com- 



plete prey list for young sandbar sharks captured in 

 Chincoteague Bay during the summer of 1983 is given 

 in Medved et al. (1985). Previous studies of young sand- 

 bar sharks along the Virginia coast also showed that 

 their diets consisted of small fish and crustaceans but 

 was dominated by soft blue crabs (Hoese 1962, Medved 

 & Marshall 1981; V.J. Lascara, Jonathan Corp., Nor- 

 folk VA, pers. commun. 1987). 



Food volumes Stomachs from 75 (79.8%) sharks con- 

 tained food varying from trace amounts to a maximum 

 of 125 mL. Nineteen stomachs (20.2%) were empty. 

 Stomachs from 236 sharks caught by gillnets in 

 Chincoteague Bay during the same time-period 

 (Medved et al. 1985) showed that 85.6% (202) held 

 food remains, while 14.4% (34) were empty. 



The mean food volume for sharks considered to be 

 newborn pups was 16.6 mL (1.2% of .fBW); for "older" 

 pups and small juveniles, it was 27.0 mL ( 1.1% of .fBW). 

 The whole sample mean was 20.0 mL or 1.2% of the 

 .fBW. 



Estimates of daily ration and annual food 

 consumption 



Daily ration Reviews are available of studies and tech- 

 niques for determining stomach evacuation rates 

 (Windell 1978, Fange & Grove 1979) and daily ration 

 (Davis & Warren 1971, Conover 1978, Mann 1978) for 

 several species of teleosts. Comparable types of stud- 

 ies for sharks are lacking in the literature, primarily 

 because the technology for maintaining sharks in a 

 healthy "normal" condition in the laboratory has not 

 been perfected (Gruber & Keyes 1981). A few excep- 



