Clam Siphon Tip Nipping by Fishes in the Estuarine Cape 

 Fear River, North Carolina 



Frank J. Schwartz 



Institute of Marine Sciences 



University of North Carolina 



Morehead City, North Carolina 28557 



ABSTRACT— Over two million fishes within 57 families and 173 

 species were collected between 1973 and 1978 in the Cape Fear 

 River, North Carolina. Sampling consisted of repetitive six-year, 22 

 station gill net (2,362 sets) and otter trawl (8,284 tows) efforts. 

 Stomachs of 82 species contained fishes. Diets of 14 species rep- 

 resenting nine fish families were found to include clam siphon tips, 

 primarily Mercenaria mercenaria. The 14 species comprised 39.7% 

 of the total catch (798,607), and examining 21,732 stomachs found 

 siphon nipping had occurred 453 times by 889 individuals (4.1%). 

 Nipping was most intense in 1976 and 1977, years when river wa- 

 ter temperatures were historically lowest, and shoal areas were subjected 

 to large expanses of ice flows. Sampling daily, weekly, and monthly 

 revealed that clam populations were patchy. Most "nipping" fishes 

 were less than 126 mm in standard length (x = 90 mm SL). Most 

 siphon tip feeding fishes were caught in September, August, and 

 October, and least in December. Nipping behavior was dominated 

 by croakers, hogchokers, southern kingfish, spot, pinfish, and fringed 

 flounders. 



Siphon tips of various molluscs have been noted in stomach contents 

 of bothid, coryphaenid, elasmobranch, gerreid, pholid, sciaenid, and 

 tetraodontid fishes (Joseph et al. 1982; McMichael and Ross 1983; 

 Modde and Ross 1983; Cyrus and Blaber 1983, 1984; Hughes 1985; 

 McMichael 1986; Cyrus 1988; Compagno 1990; Coen and Heck 1991). 

 Other animals (reviewed in Kamermans and Huiteman 1954) such as 

 crabs (Hines et al. 1990), shrimps (Kamermans and Huiteman 1994), 

 sea otters (Kvitek et al. 1991), walrus (Welsh and Martin-Bergmann 

 1990), and isopods and decapods (Bonsdorff et al. 1995) are also known 

 siphon tip nippers. 



Most siphon nipping observations have been reported following 

 food content analyses of a variety of organisms. The importance and 

 impact of siphon nipping was discussed by Armitage and Alevizon 

 (1980) and Kamermans and Huiteman (1994), who commented on the 

 poor caloric value of siphon tips. Few efforts have attempted to describe 

 the frequency of siphon tip nipping, or its effects on mollusc growth 



Brimleyana 24:33-45, April 1997 33 



