MKDVKl) KT AL.: STOMACH CONTKNTS OK SANDBAR SHARKS 



were also calculated for each of eight consecutive 3-h 

 time intervals of the day (P^ig. 2). The means ranged 

 from 1.05 to 14.92 g for fish, from 7.51 to 19.72 g for 

 crustaceans, and from 11.74 to 34.64 g for the total 

 wet weight of food in the stomachs. When 95% con- 

 fidence bounds were placed around the means, con- 

 siderable overlap of the confidence intervals was 

 observed (Fig. 2). However, the mean total wet 

 weight in the stomachs of sharks captured between 

 the time of 0130 and 0430 was considerably higher 

 than the other means, and the confidence interval for 

 the mean during this time period overlapped sub- 

 stantially with only two of the remaining seven inter- 

 vals. Similar results were obtained when food quanti- 

 ty was expressed as a percentage of shark body 

 weight. 



During the study one stomach was examined that 

 contiiined a total wet weight of 444.0 g of food 

 (10.3% BW (body weight)). This shark was not in- 

 cluded in the results presented above because the 

 quantity of food in the stomach was substantially 

 greater than for any other shark. It is mentioned 

 here because it does indicate that the stomach 

 capacity of this species is considerably greater than 

 the amount of food typically found in the stomach. In 

 an attempt to estimate maximum capacity, the 

 stomachs of 23 sharks were removed, ligated, and 

 filled with water to the point at which they were 

 about to burst. This point was determined by filling 

 several stomachs until they burst and noting the 

 changes that occurred in the stomach wall just before 

 the bursting point. The average maximum capacity 

 of the stomachs was found to be 13.0% of BW 

 (range: 8.04 to 19.8%). For sharks caught by gill nets 

 the mean quantity of food in the stomachs (0.96% 

 BW) was 7.4% of maximum capacity and the largest 

 quantity of food in a stomach (5.28% BW) was 

 40.6% of maximum capacity. 



DISCUSSION 



Several investigations conducted in other areas 

 have reported the sandbar sharks' diet to consist of 

 small crustaceans and fish (Bigelow and Schroeder 

 1948; Springer 1960; Clark and von Schmidt 1965; 

 Bass et al. 1973; Lawler 1977). With the exception of 

 squid in several stomachs, the prey items of the sand- 

 bar sharks captured in Chincoteague Bay, VA, were 

 also found to be small crustaceans and fish (Table 2) 

 and agree with those reported by Medved and Mar- 

 shall (1981) for this species in Chincoteague Bay. The 

 studies above provided little specific information con- 

 cerning the frequency of occurrence, size, relative 

 amounts, or physical state of the food items. In the 



NUMBER 



0130 0430 0730 1030 1330 1630 1930 2230 

 0430 0730 1030 1330 1630 1930 2230 0130 



TIME INTERVAL 



Figure 2. -Amount of food in the stomachs of sandbar sharks 

 caught by gill nets during various time intervals of the day. Dots in- 

 dicate mean wet weight in grams, and bars represent 2 standard 

 errors on each side of the mean. The number of stomachs examined 

 during each interval is given at the top of the figure. 



present study, small blue crabs that had recently 

 molted were, by far, the predominant food item in 

 terms of both weight and numbers. Small menhaden 

 were also found to comprise a significant portion of 

 the food consumed, but other species appeared to be 

 of minor importance in the diet of the sandbar shark 

 in the study area. 



The results of this study strongly suggest that the 

 feeding behavior of sandbar sharks in the study area 

 was characterized by relatively short periods of feed- 

 ing activity separated by substantially longer periods 

 of time during which stomach contents were digest- 

 ed and no additional feeding occurred. An indication 

 that this species may go relatively long periods of 

 time without feeding was the high percentage 

 (21.5%) of sharks that had a single food item in their 

 stomach that was in a late stage of digestion (stage 5 

 or 6). Based on the approximate duration of each 



399 



