of prey is also correlated with fish size, it can again 

 be concluded that selectivity increases with an 

 increase in densities of profitable prey 



Even though large fish at SG29 strongly 

 selected large-bodied prey, some small-bodied prey 

 showed no statistically significant change in fre- 

 quency over the entire size range of fish. These 

 small prey may still be "profitable" to capture by 

 large fish. Large fish at SG29 generally consumed 

 a wider variety of prey than small fish. The 

 number of large-sized prey species which in- 

 creased in frequency with fish size was greater 

 than the number of small-sized species which de- 

 creased with fish length. Thus, although large-size 

 fish consumed large-sized prey more often than 

 small fish, they also consumed a larger range of 

 prey sizes than did small fish. 



SUMMARY 



1. Dover sole off the Oregon coast in midsum- 

 mer of 1976 were polychaete-ophiuroid-mollusc 

 feeders, according to analysis of stomach contents. 

 Polychaetes and ophiuroids were more important 

 than molluscs and crustaceans as food in terms of 

 frequency of occurrence, weight, and numbers. 



2. Dover sole were selective feeders. Poly- 

 chaetes and ophiuroids were positively selected 

 and composed higher proportions offish diets than 

 of box core samples from the same location. Mol- 

 luscs were not generally selected. Crustaceans 

 were selected (SG29i or nonselectively consumed 

 (SGIO). 



3. Dependency of diet on fish size varied with 

 location. Dover sole sampled in a region of high 

 polychaete abundance (SG29) showed size-related 

 changes in diet. Dover sole sampled in a region of 

 relatively low polychaete abundance (SGIO) 

 showed few size-related changes in diet. 



4. When size-related changes in diet were ob- 

 served, prey body size was positively correlated 

 with predator length at which the prey taxon 

 showed a significant increase in frequency of 

 occurrence. 



5. Consumption of polychaetes by Dover sole 

 was a function of depth of prey taxon within the 

 sediment and size of the fish consuming the prey. 

 The mean depth of a prey taxon within the sedi- 

 ment was positively correlated with the predator 

 length at which the prey taxon showed a signifi- 

 cant increase in frequency of occurrence (SG29). 

 Where polychaetes were distributed closer to the 

 surface, few size-related changes were observed. 



762 



FISHERY BULLETIN: VOL. 79, NO. 4 



ACKNOWLEDGMENTS 



This study was funded by the NOAA Office of 

 Sea Grant, No. 04-5-158-2. We are especially 

 grateful to K. Jefferts, J. Dickinson, and M. 

 Richardson for identifying polychaetes, am- 

 phipods, and cumaceans, respectively, and to H. 

 Jones and E. Ruff for information on mollusc and 

 ophiuroid identification. We thank A. G. Carey, Jr., 

 who described infaunal abundances from box core 

 samples, and A. V. Tyler, who suggested statistical 

 approaches to this problem. 



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