Buckel et al,: Foraging habits of Pomatomus saltatnx 



769 



a 



was only one estimate of summer-spawned 

 daily ration for each year). 



Discussion 



Dietary analyses 



Bay anchovy was the predominant fish 

 prey of both spring- and summer-spawned 

 YOY bluefish in both 1994 and 1995. A 

 previous gut contents analysis of NEFSC- 

 NMFS bottom-trawl-collected bluefish 

 (south of Cape Hatteras to Georges Bank) 

 was conducted by Morris^ from 1978 to 

 1980. Bay and striped anchovy dominated 

 the diet of the 292 YOY bluefish (110- 

 300 mm) that he examined; butterfish and 

 squid were also important prey. The mi- 

 gration of YOY bluefish onto the shelf is 

 thought to be controlled by declines in es- 

 tuarine temperature and day length (011a 

 and Studholme, 1972). Schools of bay an- 

 chovy migrate out onto the shelf beginning 

 in September and are concentrated off 

 New York, New Jersey, and the Delmarva 

 peninsula in the autumn (Vouglitois et al., 

 1987) in a similar pattern to that of con- 

 centrations of YOY bluefish (Munch and 

 Conover, in press). The timing of bluefish 

 estuarine emigration may be linked with 

 bay anchovy movements offshore. 



Invertebrates were an important part of 

 the diet of YOY bluefish in several regions. 

 In 1994, there was a large amount of gam- 

 marid amphipods in the diets of spring- and 

 summer-spawned bluefish in the SNE re- 

 gion. In addition, mysids contributed to the 

 diet of summer-spawned fish in the C-D and 

 SOC regions of the continental shelf in 

 1994. Diets of juvenile bluefish in estuar- 

 ies are usually dominated by fish prey, but 

 at times invertebrates, such as shrimp, are 

 a major prey (Friedland et al., 1988; 

 Juanes and Conover, 1995). This pattern 

 is likely a function of prey availability and prey size. 

 Bluefish prey selectivity was related to prey abun- 

 dance in the Hudson River (Buckel et al., 1999). Bay 

 anchovy schools and invertebrate swarms are likely 

 to have patchy distributions on the shelf; the diet of 



D 1995-Spring-spawned 

 \ 



Time intervals 



Figure 4 



Gut fullness ig prey/g bluefish I for spring-and summer-spawned blue- 

 fish collected from SNE, C-D. and SOC regions of the continental shelf 

 in 1994 (A, Bl and 1995 iC, D) versus time interval of collection. Sun- 

 rise fell between the 0600 and 0900 time inter\'al and sunset fell be- 

 tween the 1800 and 2100 time interval. Error bars are ±1 SE. 



2 Morris. T. L. 1984. Food of bluefish. Woods Hole Labora- 

 tory Reference Document 84-22, Woods Hole Laboratory, North- 

 Mar. Fish. Serv.', NOAA, 

 13 p. 



east Fisheries Science Center, Natl. 

 Woods Hole. MA 02543 MED/NEFC 84-26. 



bluefish at any location will be dependent on local 

 prey availability. 



Channeled whelk has not been reported previously 

 as a prey of bluefish. The foot of channeled whelk 

 with the operculum still attached was found in sev- 

 eral bluefish in the C-D region in 1995. This may 

 have been due to opportunistic feeding on whelk that 

 had shell damage related to some fishery activity. 

 However, whelk occurred in bluefish gut contents 

 over a fairly broad geographic area and not at a single 



