KOSLOW; FEEDING SELECTIVITY OF NORTHERN ANCHOVY SCHOOLS 



such conditions, the predator may form a "search 

 image" for a particular prey item (Tinbergen 

 1960; also as discussed by Beukema 1968). How- 

 ever, planktivorous fish in marine systems typi- 

 cally have a wide variety of prey items available to 

 them. Furthermore, the relative densities of dif- 

 ferent zooplankters available to the fish will vary 

 constantly due to vertical and horizontal patchi- 

 ness of the plankters' distribution, the movements 

 of the school, and the very differences from front to 

 back of the school created by its feeding. Thus, 

 under most natural conditions, it may not be 

 feasible for planktivorous marine fish to form 

 "search images" and to select particular prey 

 items based upon their relative abundance in the 

 environment. 



Further quantitative field studies on the feed- 

 ing of marine schooling fish should enhance our 

 understanding of the role of these planktivores in 

 pelagic ecosystems. Particular questions to be 

 addressed include 1) the role their feeding plays in 

 regulating the structure of marine plankton 

 communities, and 2) the degree to which fish 

 populations themselves are regulated by inter- 

 and intra-specific predation upon the early life 

 stages. It should also be possible to study 3) the 

 relation between planktonic conditions and the 

 distribution and schooling behavior of planktiv- 

 orous fish, which is no doubt linked to their 

 availability to commercial fishing operations. 



ACKOWLEDGMENTS 



I gratefully acknowledge the cooperation in the 

 field of Roy Everingham and the EBBCO (Ev- 

 eringham Brothers Bait Company) bait fleet and 

 the ship time donated by J. Hunter and E Smith of 

 the National Marine Fisheries Service. I am grate- 

 ful to D. Goodman, J. Hunter, J. Isaacs, D. Lange, 

 and A. Larson for their careful readings of the 

 manuscript and especially to M. Mullin for his 

 continued support of this work. The comments of 

 J. Steele and an anonymous reviewer contributed 

 substantially to this paper. 



This research was supported by U.S. Depart- 

 ment of Energy Contract DE-AM03-76-SF00010 

 and NSF Grant OCE76-02035. 



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