MKI)\ Kli KTAL : STOMACH CONTENTS OF SANDBARSHARKS 



Table 1. — Number of sharks caught for stomach 

 content analysis during different time intervals 

 and by the two capture methods. 



Time interval 



Rod and reel Gill net Total 



2230-0130 

 0130-0430 

 0430-0730 

 0730-1030 

 1030-1330 

 1330-1630 

 1630-1930 

 1930-2230 

 Total 



19 

 11 

 20 

 21 

 27 

 39 

 18 

 23 

 178 



33 

 27 

 20 

 27 

 27 

 39 

 30 

 33 

 236 



52 



38 

 40 

 48 

 54 

 78 

 48 

 56 

 414 



animals that were measured and weighed: Wt = 

 0.0123 (FL)-^'^'" (v = 369, R- = 0.97). Water 

 temperature during the fishing periods ranged from 

 20.0° to 27.3°C {n = 172, x = 25.1) but 90% of the 

 temperatures were between 23.9° and 26.4° C. 



Fifteen different food types were identified in the 

 stomachs (Table 2). A relatively large number of 

 stomachs (« = 74, 17.9%) were empty, and unidenti- 

 fiable fish remains occurred in others (n = 21, 5.1%). 

 The blue crab was the most frequently occurring 

 food item and was found in 279 (67.4%) of the 

 stomachs examined and in 82.1% of the stomachs 

 containing food. Of the food remains that could be 

 positively identified as individual blue crabs (n = 

 309), 88.0% of the crabs had recently molted and 

 were soft. The crabs that could be measured ranged 

 in size from 1.0 to 14.0 cm between the two points of 

 the carapace (n = 136, x = 7.4). Although exact 

 numbers were difficult to determine, it appeared 

 that less than half of the blue crabs were consumed 

 whole. The only other prey frequently found was the 

 Atlantic menhaden, which occurred in 55 (13.3%) of 

 the stomachs examined and in 16.2% of the 

 stomachs with food. Of the 61 cases where it was 

 possible to determine if the fish was consumed whole 

 or in part, 28 (45.9%) of the menhaden were whole 

 and ranged in size from 5 to 10 cm total length (TL) 

 (x = 7.3). The estimated sizes of the partially eaten 

 menhaden ranged from 5 to 17 cm TL (x = 8.6). All 

 other prey items were found in < 6.0% of the 

 stomachs examined. 



The distributions of stage-of-digestion values 

 assigned to the food items in the stomachs of sharks 

 caught by the two different fishing methods are 

 shown in Figure 1. The distribution for sharks 

 caught by rod and reel indicated that 71.8% of the 

 food items were in either the first or last stage of 

 digestion. In contrast, food items in the stomachs of 

 sharks caught by gill nets were divided more evenly 

 among all the stages of digestion. The two capture 

 methods also differed in the proportion of sharks 



Table 2— Stomach contents found in a sample of 414 sand- 

 bar sharks. 



Stomach content 



No. of 



stomachs 



found in 



Percent of 



stomachs 



found in 



Blue crab, Call nee ties sapidus 



Empty 



Atlantic menhaden, Brevoortia 



tyrannus 

 Summer flounder, Paralichthys 



dentatus 

 Unidentified fish 

 IVIantis shrimp, Squilla emprisa 

 American eel, Anguilla rostrata 

 Spot. Leiostomus xanthurus 

 Atlantic silverside, Menidia 



menldia 

 Smooth dogfish, Mustelus canis 

 Northern pipefish. Syngnathus 



fuscus 

 Anchovy, Anchoviella mitchilll 

 Squid, Loligo pealei 

 Bluefish, Pomatomus saltatrix 

 Calico crab, Ovalipes ocellatus 

 Mummichog, Fundulus 



heteroclitus 

 Northern seahorse. 



Hippocampus hudemius 



279 



74 



55 



24 

 21 

 18 

 15 

 14 



9 



7 



6 

 5 

 5 

 3 



1 



1 

 1 



67.4 

 17.9 



13.3 



5.8 

 5.1 

 4.4 

 3.6 

 3.4 



2.2 

 1.7 



1.5 

 1.2 



1.2 

 0.7 

 0.2 



0.2 



0.2 



caught with empty stomachs. The percentage of the 

 178 sharks caught by rod and reel with empty 

 stomachs (22.5%) was significantly higher than that 

 found for the 236 sharks caught by gill nets (14.4%; 

 ^-test, P = 0.015). 



Of the 414 stomachs examined, 203 contained a 

 single food item. A stage-of-digestion value of 5 or 6 

 was assigned to 89 (43.8%) of these items, indicating 

 that many sharks went at least the time equivalent of 

 5 stage-of-digestion units between meals (48 to 60 h 

 for crustacean prey or 60 to 75 h for fish prey). 



Multiple food items were found in 137 stomachs. 

 The difference between the stage-of-digestion values 



NET ROD-REEL 



^ 50-, N = 338 N = 195 



iiiiiii Li 



1 2 3 4 5 6 



2 3 4 5 6 



STAGE OF DIGESTION 



FiGt_iRE 1.- Distributions of stage-of-digestion values assigned to 

 food items present in the stomachs of sharks caught with gill net 

 and rod and reel. 



397 



