Steimle et al.: Predator-prey relationships of Pleuronectes americanus 



617 



Predation influence on benthic populations 

 and energetics 



Strong selective predation by winter flounder on cer- 

 tain benthic macrofaunal taxa can influence the 

 population dynamics of these prey and be a factor in 

 interpreting benthic community change relative to 

 disposal abatement. This affect may be evident in 

 the predation-abundance patterns for Capitella sp., 

 although the decline in the abundance of this spe- 

 cies could be a result of its short life span as well as 

 predation. 



A short life span is not a factor for P. affinis as it 

 lives for up to two years (Steimle et al. 1990). How- 

 ever, since winter flounder are visual predators 

 (Klein-MacPhee, 1978; Bharadwaj, 1988), P. affinis 

 may be at greater risk to predation because it is rela- 

 tively large (up to 7.5 cm in length and 0.5 cm in 

 width) and lives in vertical burrows with its fanned, 

 setaceous cephalic cage (head and bristles) usually 

 exposed. It also actively probes the sediment surface 

 with feeding palps that may attract predator atten- 

 tion (J. Vitaliano, personal observ.; P. Ferri 1 ). The 

 persistent abundance and strong predation on P. 

 affinis by winter flounder (Fig. 3) and other preda- 

 tors at station R2 (Steimle and Terranova, 1991; 

 Steimle, in press) is interesting in that it suggests 

 that this prey must be very productive in this area 

 to sustain heavy predation pressure. This sugges- 

 tion is supported by results of a previous study of 

 the secondary production of this species that found 

 it to be almost twice as productive near R2 as at NY6 

 and NYU (Steimle et al., 1990). 



The results of this study are subject to potential 

 biases inherent in most stomach content analyses, 

 such as differential digestion of different prey types 

 (MacDonald et al., 1982). Partial digestion of prey 

 can underestimate a prey's contribution to diets 

 based on stomach volume. Thus, the estimated pro- 

 portional contribution to diets of some soft-bodied 

 prey will be conservative. This study also assumes 

 that the stomach contents of fish represented feed- 

 ing at or very near where the benthic infauna samples 

 were collected (Steimle, in press) and that if a large 

 proportion of the prey was consumed in nearby ar- 

 eas, the benthic community structure did not differ 

 substantially from that at the actual benthic collec- 

 tion site. Some preliminary data from peripheral 

 benthic stations sampled during the study suggest 

 that this assumption was valid, although there were 

 substantial changes in community structure in some 

 parts of the trawling zones (Fromm, personal observ.). 



Ferri. P., U.S. Environmental Protection Agency. Narragansett, 

 RI 02882. Personal Commun.. 1992. 



In summary, diets of winter flounder in the New 

 York Bight apex 1) were dominated by a few prey 

 species, typically polychaetes, an anthozoan, and 

 small crustaceans; 2) showed a preference for the 

 energy-rich polychaete Pherusa affinis; 3) suggested 

 there was underutilization or "avoidance" of molluscs 

 and rhynchocoels; and 4) showed that apparent re- 

 sponses of some benthic macrofaunal species 

 (Capitella sp. and U. irrorata) to cessation of sludge 

 disposal and natural fluctuations in abundance were 

 reflected in corresponding changes in their use as prey. 



Acknowledgments 



We thank S. Fromm, C. Zetlin, and R. Koch for their 

 contribution to data processing and graphics, and D. 

 Packer, S. Chang, D. Mountain, and others for help- 

 ful comments and suggestions. 



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