FISHERY BULLETIN: VOL. 80, NO. 3 



ergy per individual item. Two fortuitous conse- 

 quences of this size-dependent predation may be 

 important. First, the dietary overlap between 

 small juveniles and larger fish is minimized, 

 thus conserving food stocks for recently settled 

 individuals. Second, both siphons and palps are 

 capable of being regenerated. By consuming 

 only parts of benthic organisms, food sources are 

 not destroyed and may be cropped again in later 

 months by other individuals following regenera- 

 tion. This may be particularly important in the 

 case of English sole because juveniles are contin- 

 uously recruited to the bottom over a 9-mo period 

 (Krygier and Pearcy footnote 2). 



The four pleuronectiform fishes we studied 

 form a trophic continuum, ranging from gener- 

 alists feeding upon numerous benthic prey (P. 

 vetulus) to specialists relying on a few pelagic 

 food items {Psettichthys melanostictus). Isopsetta 

 isolepis and C. stigmaeus are intermediate in 

 their position on the continuum. Few published 

 results exist with which to compare ours. Cailliet 

 et al. (1979) investigated the food habits of Par- 

 ophrys vetulus, C. stigmaeus, and Psettichthys 

 melanostictus at an ocean station in Monterey 

 Bay. The fish they examined were all larger than 

 the ones for which we have data, but the same 

 basic trends emerge. They found that English 

 sole was a generalist, eating a wide variety of 

 benthic food items; sand sole relied almost totally 

 on mobile crustaceans for food; and speckled 

 sanddab fed on pelagic and epibenthic Crustacea 

 and occasional infaunal worms and molluscs. 

 Wakefield (footnote 3) has studied the adult food 

 habits of these three species as well as those of /. 

 isolepis collected at the Moolach Beach site. 

 Although the specific food items ingested differ 

 for recently settled juveniles and adults at this 

 site, the basic modes of feeding, e.g., infaunal 

 generalist or pelagic specialist, remained un- 

 changed at Moolach Beach as the youngest juve- 

 niles mature to adults. 



The greatest similarity among diets is between 

 those of Parophrys vetulus and /. isolepis. Both of 

 these benthophagous species have similar mouths 

 with small, asymmetrical jaws and small incisor 

 teeth. Both complete metamorphosis and com- 

 mence benthic feeding at the same size (18-20 

 mm SL). Qualitatively there is no difference in 

 their diet, although quantitatively butter sole 

 occasionally feed more heavily on mysids. Com- 

 paring fish of the same size (17-35 mm SL) on 29 

 May 1979, P. vetulus and /. isolepis fed on the 

 same prey items in the same proportions. If food 



should be limiting for these two species, then in 

 the absence of subsequent shifts in food prefer- 

 ence the potential exists for competitive inter- 

 action. While observing the feeding behavior of 

 P. vetulus in the laboratory, several butter sole 

 were placed in the aquaria along with the Eng- 

 lish sole. Isopsetta isolepis were observed to bite 

 the fins of P. vetulus and pursue them around the 

 tank. These were casual observations which 

 were only replicated over a 2-d period. Should 

 this aggressive behavior be substantiated by fur- 

 ther work, then interference competition be- 

 tween P. vetulus and /. isolepis in the Moolach 

 Beach area seems likely. On the whole, however, 

 English and butter soles do not settle at the same 

 time or place. Parophrys vetulush&s a protracted 

 benthic recruitment period, settling to the bot- 

 tom between November and July in estuarine 

 and coastal waters <30 m deep (Krygier and 

 Pearcy footnote 2). Isopsetta isolepis, on the other 

 hand, has a restricted settling period (May- 

 August) yet occurs over a broader depth range 

 (9-60 m)(Krygier and Pearcy footnote 2). If inter- 

 specific interactions were occuring between 

 English and butter soles, it is likely that they 

 would be limited to regions of overlap like Moo- 

 lach Beach in the summer months. 



ACKNOWLEDGMENTS 



We wish to thank E. Krygier, W. Pearcy, and 

 A. Rosenberg for making available to us their 

 collections of fish. C. D. Mclntire, C. B. Miller, 

 W. G. Pearcy, G. Boehlert, and W. W. Wakefield 

 have read and commented on the manuscript. 

 This work is a result of research sponsored by the 

 Oregon State University Sea Grant College Pro- 

 gram supported by NOAA, Office of Sea Grant, 

 U.S. Dep. of Commerce, under grant NA79AA- 

 D-00106. 



LITERATURE CITED 



Cailliet, G., B. S. Antrim, and D. S. Ambrose. 



1979. Trophic spectrum analysis of fishes in Elkhorn 

 Slough and nearby waters. In S. J. Lipovsky and C. A. 

 Simenstad (editors), Gutshop '78 fish food habits studies. 

 Proc. Second Pac. Northwest Tech. Workshop, October 

 10-13, 1978, p. 118-128. Univ. Wash. Press, Seattle. 

 CUSHING, D. H., AND J. G. K. HARRIS. 



1973. Stock and recruitment and the problem of density 

 dependence. Rapp. P.-V. Reun. Cons. Perm. Int. Ex- 

 plor. Mer 164:142-155. 

 Edwards, R., and J. H. Steele. 



1968. The ecology of 0-group plaice and common dabs at 



564 



