Buckel and Conover: Movements, feeding, and daily ration of Pomatomus saltatrix 
677 
Bluefish collected by gill net and surface trawls 
had diets that were similar to those of bluefish cap- 
tured with beach seines (Table 1-3). This finding 
suggests that YOY bluefish feed nearshore and then 
move offshore or that prey types in offshore shoal 
feeding areas do not differ from prey nearshore (or 
both). However, bluefish captured by surface trawls 
in 1993 had a larger amount of bay anchovy in their 
diet than did bluefish captured with beach seines 
during the previous week. This finding may reflect 
increased availability of bay anchovy in offshore sur- 
face waters than in nearshore environments. 
Implications 
This study provides an improved understanding of 
the temporal and spatial patterns of bluefish feed- 
ing ecology in the Hudson River estuary. Knowledge 
of the temporal and spatial scales at which preda- 
tors forage is required for a variety of predator-prey 
studies. Densities of predator and prey at scales rel- 
evant to predator foraging should be used for calcu- 
lations of prey-type selectivity (O’Brien and Vinyard, 
1974), in encounter rate models (see Brandt and 
Mason, 1994), in functional and numerical response 
calculations (Peterman and Gatto, 1978), and in cal- 
culations of a predator’s growth or impact (Brandt 
and Kirsch, 1993; Petersen, 1994). 
Empirical data on the diel changes in spatial over- 
lap of fish and their prey and the timing of foraging 
activity is often lacking from spatially explicit mod- 
els of fish feeding and growth. For example, Brandt 
and Kirsch ( 1993) used estimates of prey density from 
offshore nighttime collections. If the sampling design 
for estimating the densities ofYOY bluefish and their 
prey in the Hudson River were constrained to only 
offshore or night (or both), the peaks in feeding ac- 
tivity that occur during day and crepuscular periods 
in the nearshore would be missed. Clearly, a detailed 
understanding of the spatiotemporal movement and 
feeding patterns of predators and prey are necessary 
to produce realistic models of feeding and growth 
(Mason and Patrick, 1993). 
Acknowledgments 
This work would not have been possible without the 
help of many volunteers, including T. Anderson, J. 
Brown, B. Childers, B. Connelly, A. Divadeenam, A. 
Ehtisham, L. LeBlanc, D. Lewis, C. Lobue, A. 
Matthews, N. Murray, R. Pantol, A. Parrella, B. 
Puccio, K. Reynolds, F. Scharf, J. Schell, K. 
Stansfield, G. Stone, and especially F. Edwards, D. 
Gardella, T. Hurst, and N. Steinberg. We thank them, 
as well as R. Cerrato, M. Fogarty, and E. Schultz, for 
statistical and programming advice, and M. Wiggins, 
for suggestions with surface trawl methods. K. 
McKown and B. Young provided advice and data 
which aided in site location. We also acknowledge 
personnel from Westchester County, NY Parks and 
Recreation, for access to Croton Point Park and per- 
sonnel from Washington Irving Yacht Club for the 
use of their boat storage and ramp facilities. Critical 
reviews of the manuscript were provided by R. 
Cerrato, R. Cowen, M. Fogarty, G. Lopez, and N. 
Steinberg. This research was funded by a research 
grant from the Hudson River Foundation for Science 
and Environmental Research Inc. and by the Na- 
tional Oceanic and Atmospheric Administration 
award number NA90AA-D-SG078 to the Research 
Foundation of SUNY for the New York Sea Grant 
Institute. 
Literature cited 
Boisclair, D., and W. C. Leggett. 
1991. If computers could swim or fish could be programmed: 
a response to comments by Hewett et al. (1991). Can. J. 
Fish. Aquat. Sci. 48:1337-1344. 
Boisclair, D., and F. Marchand. 
1993. The guts to estimate fish daily ration. Can. J. Fish. 
Aquat. Sci. 50:1969-1975. 
Brandt, S. B., and J. Kirsch. 
1993. Spatially explicit models of striped bass growth in the 
mid-Chesapeake Bay. Trans. Am. Fish. Soc. 122:845-869. 
Brandt, S. B., and D. M. Mason. 
1994. Landscape approaches for assessing spatial patterns 
in fish foraging and growth. In D. J. Stouder, K. L. Fresh, and 
R. J. Feller (eds. ), Theory and application in fish feeding ecol- 
ogy, p. 211-238. Univ. South Carolina Press, Columbia, SC. 
Buckel, J. A. 
1997. Impact of bluefish (Pomatomus saltatrix) predation 
on estuarine and continental shelf fishes. Ph.D. diss., 
State Univ. New York, Stony Brook, NY, 199 p. 
Buckel, J. A., and D. O. Conover. 
1996. Gastric evacuation rates of piscivorous young-of-the- 
year bluefish. Trans. Am. Fish. Soc. 125:591-599. 
Buckel, J. A., N. D. Steinberg, and D. O. Conover. 
1995. Effects of temperature, salinity, and fish size on 
growth and consumption of juvenile bluefish. J. Fish Biol. 
47:696-706. 
Burrows, M. T., R. N. Gibson, L. Robb, and C. A. Comely. 
1994. Temporal patterns of movement in juvenile flatfishes 
and their predators: underwater television obser- 
vations. J. Exp. Mar. Biol. Ecol 177:251-268. 
Caulton, M. S. 
1978. The importance of habitat temperatures for growth 
in the tropical cichlid Tilapia rendalli Boulenger. J. Fish 
Biol. 13:99-112. 
Clark, C. W., and D. A. Levy. 
1988. Diel vertical migrations by juvenile sockeye salmon 
and the antipredation window. Am. Nat. 131:271-290. 
Conover, D. O., and B. E. Kynard. 
1984. Field and laboratory observations of spawning peri- 
odicity and behavior of a northern population of the Atlan- 
