FEEDING BEHAVIOR AND BIOLOGY OF YOUNG SANDBAR SHARKS, 



CARCHARHINUS PLUMBEUS (PISCES, CARCHARHINIDAE), IN 



CHINCOTEAGUE BAY, VIRGINIA* 



Robert J. Medved^ and Joseph A. Marshall^ 



ABSTRACT 



During the summers of 1977, 1978, and 1979 the feeding behavior and biology of young sandbar 

 sharks were investigated in Chincoteague Bay, Virginia, using catch data obtained from rod and reel 

 fishing. Mean catch per unit effort for the study was 1.02 sharks per hour, but yearly differences in 

 catch per unit effort were found. Sandbar sharks were not caught before the first week in June 

 despite substantial fishing effort prior to this time, both in 1977 and 1978. Catch per unit effort was 

 higher at night than during the day but was not related to tidal current stage or speed. Captures were 

 made at surface, mid, and bottom fishing depths. During the day, catch per unit effort was highest at 

 the bottom fishing depth but did not differ among the three depths during the night. The blue crab, 

 Callinectes sapidus, was found in 41.3'7e of the stomachs examined; 20% of the stomachs were empty, 

 and the remainder contained various crustaceans and fishes. The proportion of empty or nearly 

 empty stomachs was greater for night captures than for day captures. Yearly differences in sex ratio 

 existed and the total length distribution of sharks measured suggested the presence of relatively 

 distinct size classes. 



The natural history of the sandbar shark, Car- 

 charhinus plumbeus, has received considerable 

 attention and is relatively well known. Tag re- 

 turns (Casey 1976) and analysis of commercial 

 shark fishery records (Springer 1960) have pro- 

 vided valuable information on the distribution 

 and long-term movements of this species. These 

 studies show the sandbar shark to be an abun- 

 dant, migratory shark distributed in the western 

 North Atlantic from Cape Cod, Mass., to West 

 Palm Beach, Fla., during the summer and from 

 the Carolinas into the Gulf of Mexico in the 

 winter. From spring until late fall, young sand- 

 bar sharks spend much of their time along the 

 mid-Atlantic coast in nursery areas consisting of 

 shallow bays and sounds. In late fall the young 

 move farther offshore and south to wintering 

 grounds between North Carolina and Florida. 

 According to Casey (1976), the young may repeat 

 this cycle for up to 5 yr and then begin to occupy 

 areas farther offshore and undertake longer 

 north-south migrations. Other studies have made 

 contributions concerning growth (Wass 1973), 



^Contribution No. 1, Wallops Island Marine Science Center. 



^Department of Biology, West Virginia University, Morgan- 

 town, W. Va.; present address: Graduate School of Oceanography, 

 University of Rhode Island, Kingston, RI 02881. 



^Department of Biology, West Virginia University, Morgan- 

 town, WV 26506. 



reproduction (Taniuchi 1971), and general ecol- 

 ogy (Bigelow and Schroeder 1948; Clark and von 

 Schmidt 1965; Bass et al. 1973; Lawler 1977). 



One area in which information is lacking, not 

 only for this species but for sharks in general, 

 concerns feeding behavior. Although work has 

 been conducted on the prey items of sharks 

 (Bigelow and Schroeder 1948) and the role of 

 various sensory modalities in locating prey (Hob- 

 son 1963; Kleerekoper 1969; Myrberg et al. 1976; 

 Hodgson and Mathewson 1978; Kalmijn 1978), 

 these areas have received little attention and are 

 little understood. Other areas of feeding behavior 

 such as food requirements and feeding activity 

 have received even less attention. 



The specific objective of this study was to 

 determine patterns of feeding activity of young 

 sandbar sharks in relation to the time of day, 

 tidal cycle, and vertical positions within the 

 water column. Because information on sandbar 

 sharks in nursery areas is scarce, data concern- 

 ing the food items, abundance, sex ratio, and age- 

 class composition of this species in Chincoteague 

 Bay are also presented. 



METHODS 



This study was conducted from early May 

 through late August during 1977 and 1978 and on 



Manuscript accepted April 1981. 



FISHERY BULLETIN: VOL, 79, NO. 3, 1981. 



441 



