STOMACH CONTENTS OF 



YOUNG SANDBAR SHARKS, CARCHARHINUS PLUMBEUS, 



IN CHINCOTEAGUE BAY, VIRGINIA' 



Robert J. Medved,^ Charles E. Stillwell,^ and 

 John J. Casey» 



ABSTRACT 



nurinp the summer of \WA the stcmiach contents of 414 sandbar sharks captured by j^ll nets, and nnl and 

 reel fishing gear in Chincoteague Bay, Virginia, were examined. The blue crab, CaUinectes mpidui<, occur- 

 red in 67.4% of the stomachs and Atlantic menhaden, Brevoortia tyrannus, occurred in 13.3% of the 

 stomachs. Other species of small crustaceans and fishes were found in < 6.0% of the stomachs, and 17.9%i of 

 the stomachs were empty. Data collected concerning the amount, stage of digestion, and number of food 

 items in the stomachs indicated that feeding occurred during relatively short periods of time separated by 

 long pericKis during which food was digested and no additional food was consumed. Sharks caught in gill 

 nets were found to be in various stages of the feeding cycle and were more representative of the entire 

 population than those caught by rod and reel. In the stomachs of these sharks, crustaceans accounted for 

 nearly twice as much of the mean weight of food as did fish. The mean quantity of food in the stomachs was 

 0.96% of body weight (BW) and the maximum quantity was 5.28% of BW. The quantity of food in all 

 stomachs was significantly less than the estimated maximum stomach capacity (13.0% BW). Sharks caught 

 between 0130 and 0430 were found to contain considerably more food in their stomachs than sharks caught 

 during other times of the day. The data collected from this study when combined with information concern- 

 ing gastric evacuation will provide the basis for food consumption estimates in this species. 



Traditionally the management of commercially 

 valuable fisheries has been based on single-species 

 production models and the concept of maximum sus- 

 tainable yield (Hennemuth 1979). Although general- 

 ly accepted as an objective of management, the esti- 

 mation and application of maximum sustainable yield 

 have not provided satisfactory results and have, in 

 fact, led to significant declines of some traditional 

 and highly valued fisheries (Edwards and Henne- 

 muth 1975; Hennemuth 1977; Holt and Talbot 

 1978). The poor results of single-species models in 

 allocating fishing quotas may be due in part to the 

 fact that they assume no interactions of the target 

 species with other components of the ecosystem. In 

 recent years it has become clear that this assumption 

 is unrealistic and that variables such as competition, 

 predation, and abiotic factors should be considered in 

 any assessment of fishery productivity and potential 

 yields to man. It has been pointed out(Gulland 1978, 

 1983; Mercer 1982) that the future success of our 



iMARMAP Contribution No. MED/NEFC 84-02. 



^University of Rhode Island, Graduate School of Oceanography, 

 Narragansett, RI; present address: Northeast Fisheries Center 

 Narragansett Laboratory, National Marine Fisheries Service, 

 NOAA, South Ferry Road, Narragansett, RI 02882. 



^Northeast Fisheries Center Narragansett Laboratory, National 

 Marine Fisheries Service, NOAA, South Ferry Road, Narragansett, 

 RI 02882. 



attempts at managing fishery resources will depend, 

 to a large extent, on our ability to develop multi- 

 species production models that adequately account 

 for interactions among species. An important compo- 

 nent of these models is predator-prey interactions. In 

 fact, collection of data on the diets of the major 

 predators is considered absolutely necessary for the 

 progress of multispecies assessment techniques 

 (Hennemuth 1980^; Mercer 1982). Considering their 

 position as one of the most abundant apex predators 

 in the sea, predation by sharks undoubtedly plays a 

 major role in the exchange of energy in the marine 

 environment. In fact, a study by Jones and Geen 

 (1977) has indicated that the spiny dogfish, Squalus 

 acanthias, in British Columbia waters annually con- 

 sumes over 5 times the commercial catch of herring 

 and up to 44% of the total stock. The impact that 

 sharks have on commercial fisheries can only be 

 determined by knowing the diversity of prey items 

 and the biomass of each consumed. While numerous 

 publications on sharks incorporate lists of items 

 found in their stomachs, very little is known about 

 daily ration and the amounts of food consumed an- 

 nually. 



■•Hennemuth, R. C. 1980. Research needs for multispecies 

 fisheries. Office of Technology Assessment Workshop, Seattle, 

 WA., 21-23 April. 



Manuscript accepted October 1984. 



FISHERY BULLETIN: VOL. 83, NO. 3, 1985. 



395 



