374 



Stomach contents of juvenile cobia, 



Rachycentron canadum, 



from the northern Gulf of Mexico 



James S. Franks 



Gulf Coast Research Laboratory 



PO Box 7000 



Ocean Springs. Mississippi 39566-7000 



Nikola M. Garber 



Gulf Coast Research Laboratory 



PO Box 7000 



Ocean Springs. Mississippi 39566-7000 



Present address: Bowling Green State University 

 3 I 3 Harshman-Bromfield 

 Bowling Green, Ohio 43403 



James R. Warren 



Gulf Coast Research Laboratory 



PO Box 7000 



Ocean Springs, Mississippi 39566-7000 



The cobia. Rachycentron canadum, 

 is a monotypic member of the fam- 

 ily Rachycentridae. It is a migra- 

 tory pelagic fish that occurs world- 

 wide in tropical, subtropical, and 

 warm temperate seas, except in the 

 central and eastern Pacific Ocean 

 (Shaffer and Nakamura. 1989). In 

 the western Atlantic, the cobia oc- 

 curs from Massachusetts and Ber- 

 muda to Argentina i Briggs, 1958) 

 but is most common in the Gulf of 

 Mexico (Migdalski and Fichter, 

 1983), ranging from Key West, 

 Florida, along the Gulf coa 

 Campeche, Mexico I Dawson. 1971 ). 



Some individual cobia an 

 sonal migrants, moving from win- 

 tering grounds near the Florida 

 Keys into the Gulf of Mexico dur- 

 ing spring, generally entering 

 northern Gulf waters from April 

 through May and returning to the 

 wintering grounds during late fall 

 and early winter (Franks et al.. 

 1991; Biesiotetal., 1994). The tim- 

 ing o nigrations may relate 



to the availability of important prey 

 species (Darracott, 1977). 



A few observations on the food 

 habits of adult R. canadum from 

 the Gulf' Gulf of Mexico i have been 

 reported. Knapp (1951) listed the 

 stomach contents of 24 cobia taken 

 near Port Aransas, Texas, and 

 Miles (1949) briefly discussed the 

 foods of 11 cobia from Aransas Bay. 

 Texas. Reid (1954) mentioned the 

 stomach contents of a single adult 

 taken in the vicinity of Cedar Key. 

 Florida, and Boschung (1957) re- 

 marked on the prey in four cobia 

 collected off coastal Alabama. 

 Christmas et al. 1 reported the prey 

 of 11 adult cobia taken off Missis- 

 sippi. A brief review of reported 

 foods of cobia was presented by 

 Shaffer and Nakamura (IV 

 Stomach contents of 287 cobia 

 caught by hook and line in the 

 northern Gulf of Mexii 

 ational fishery, mostly adults taken 

 off Mississippi, were reported by 

 Meyer and Franks i L996). None of 



these studies identified which prey, 

 if any, were specifically consumed by 

 juvenile cobia, rather, these observa- 

 tions were reported either for adults, 

 for a size range comprising both ju- 

 veniles and adults, or for cobia "in 

 general." This paper represents the 

 first study describing specifically the 

 diet of juvenile R. canadum. 



Knowledge of the feeding habits 

 of juvenile cobia is necessary for 

 understanding the role of diet in 

 the recruitment processes of this 

 economically important species and 

 is a necessary prerequisite for man- 

 agement of this resource. The spe- 

 cific objective of this study was to 

 analyze quantitatively the diet of 

 juvenile cobia from the northern 

 Gulf of Mexico. 



Methods 



Juvenile cobia were collected by 

 trawl during fisheries resource sur- 

 veys conducted in the northern Gulf 

 of Mexico by the National Marine 

 Fisheries Service (NMFS), South- 

 east Fisheries Science Center, 

 Pascagoula, Mississippi. Fish were 

 collected in July (n=7 ) and Septem- 

 ber i«=40> 1993 and in March (n=2) 

 1994 north of lat. 28°32'N and be- 

 tween long. 85"40'W and long. 

 93°55.4'W (Fig. L). Most of the 

 specimens (71%) were collected 

 during September 1993 off Missis- 

 sippi and Alabama. Bottom water 

 depth ranged from 9 to 6 m. 



Collection gear included a 28-m 

 high-profile fish trawl with 0.6-cm 

 codend mesh; a 19-m "western jib" 

 shrimp trawl with 4-cm codend 

 mesh: a 17-m "mongoose" shrimp 

 trawl with 4-cm codend mesh; and 



I R S. 

 Waller. 1974. Investigations oi 

 Gulf Coasl Ri 

 Laboratory, P.O. Box 7000. ( )cean Springs, 



00. Completion Rep 

 IT S, Bur Comm. Fish, Proj. 2-128-R, 105 

 P- 



ited 13 Decembi 

 Fishen Bulletin 



