144 



Fishery Bulletin 91(1), 1993 



FLATFISH 



GOOSEFISH 



BLUEFISH 



GADIDS 



SCOMBRIDS 



OTHER TELEOSTS 



ALL TELEOSTS 



ELASMOBRANCHS 



CEPHALOPODS 



MISCELLANEOUS 



10 



20 



30 40 



PERCENT 



50 



60 



70 



Figure 2 



Major food categories consumed by 321 juvenile and adult sandbar sharks Carcharhinus 

 plumbeus from the U.S. northeast coast, 1972-84. 



probably linked to prey density, since 7 of the 11 stom- 

 achs containing squid were from sharks captured off- 

 shore where squid are most abundant. It is also pos- 

 sible that the four sharks captured nearshore with 

 squid in their stomachs had moved inshore after eat- 

 ing the squid. 



Areal comparisons Flatfish and cephalopods were the 

 only food groups to show significant differences (P<0.05, 

 X 2 test) in importance between the areas. Flatfish oc- 

 curred most often in nearshore stomach samples, prob- 

 ably as a result of their high summer abundance in 

 shoaler waters along the coast (Bigelow & Schroeder 

 1953). Cephalopods occurred more often in stomachs 

 offshore because of their high abundance off the U.S. 

 northeast coast (Lange & Sissenwine 1980, Lange 

 1982), and hence their availability probably accounts 

 for their appearance in the stomachs examined in this 

 study. 



Nearshore there was significantly (P<0.05, x 2 test) 

 more predation on elasmobranchs and goosefish by fe- 

 male sharks than by males. Offshore, juvenile males 

 consumed significantly (P<0.05, x 2 test) more 'Other 

 Teleosts' than females. 'Other Teleosts' was the only 

 food group in this area for which there was a differ- 

 ence between sexes. Overall, there was no difference 



in predation rates on the major 

 food groups with respect to shark 

 size (juveniles or adults). 



Food volumes Overall, 49% of 

 examined stomachs contained 

 food. Wass ( 1973) found that 45% 

 of stomachs from sandbar sharks 

 captured by hook-and-line off 

 Hawaii contained food remains. 

 In other studies, averages have 

 been lower, but up to 29%* have 

 been observed for the sandbar 

 shark (Springer 1960, Bass et al. 

 1973, Lawler 1976). 



Our findings show that stom- 

 ach content volumes ranged from 

 trace amounts to a maximum 

 of 3102 mL, with a mean of 

 144 mL. The mean for adults was 

 175.4 mL and 125.2 mL for juve- 

 niles. Stomachs from adult and 

 juvenile females contained more 

 food (184.0 and 165.0 mL) on the 

 average than their male counter- 

 parts (125.0 and 97.0 mL); how- 

 ever, differences were not signifi- 

 cant at the oc=0.05 level (Mest). 

 The ratio of stomach content 

 volume to mean body weight (.vBW) varied between 

 different groups of the population, from a low of 0.30% 

 for adult males to a high of 0.83% for juvenile males 

 offshore. The mean for adults and juveniles was 0.33% 

 and 0.55%, respectively, with an overall sample mean 

 of 0.42%. Means for adults of both sexes were similar 

 for the whole sample and nearshore, ranging from 0.30 

 to 0.36%. Juvenile males and females from nearshore 

 differed the most, with percentages of 0.42 and 0.66, 

 respectively. The highest stomach content values were 

 from an adult and a juvenile female. Stomach con- 

 tents in these sharks amounted to 5.35 and 5.34% of 

 their body weight, respectively. The adult's stomach 

 contained a whole smooth dogfish and gadid remains. 

 The stomach from the juvenile contained 10 yellowtail 

 flounder Limanda ferruginea and a small goosefish. 

 The flounders (x size=13.4cm) may have been con- 

 sumed as natural prey or obtained as culls from a 

 trawl catch. However, other sandbar sharks caught in 

 the area on the same day contained only 1 or 2 flounder, 

 suggesting that this juvenile female was more success- 

 ful in obtaining natural prey. 



Overall mean stomach volume in terms of liquid 

 capacity for the sharks in this study was 2.62 L which 

 was 7.7% of the *BW (34.0kg). For adults, the mean 

 was 5.15 L, amounting to 10.0% of their .tBW (52.3 kg). 



