Steimle et al.; Predator-prey relationships of Pleuronectes amencanus 



615 



70 

 60 

 50 

 40 

 30 

 20 

 10 

 



9 10 11 12 1 

 86 I 



23456789 10 11 12 1234567 

 87 I 88 I 



collection periods 



benthic biomass 



stomach volume 



Figure 4 



Trends in the percent contribution of the pollu- 

 tion-tolerant polychaete Capitella sp. to total 

 stomach volume of winter flounder, Pleuronectes 

 americanus, compared to the polychaete's percent- 

 age contribution to total benthic macrofaunal bio- 

 mass at NY6, the station most affected by sewage 

 sludge disposal and its cessation, in the New York 

 Bight apex. 



Figure 5 



Trends in the frequency of occurrence of the am- 

 phipod Unciola irrorata in the diet of winter floun- 

 der, Pleuronectes americanus, compared to its nu- 

 merical abundance in the benthic macrofaunal 

 community at two stations in the New York Bight 

 apex variably affected by sewage sludge disposal 

 and its cessation in December 1987. 



With the exception of P. affinis and per- 

 haps C. irroratus, there is limited evidence 

 of prey preference by winter flounder. This 

 is consistent with the results of many quali- 

 tative winter flounder feeding studies that 

 report a diverse diet, but also with limited 

 evidence of a prey species' preferences (Tyler, 

 1972; Klein-MacPhee, 1978; Keats, 1990). 



However, several dominant members of the 

 benthic macrofaunal community at the three 

 study stations were not commonly consumed 

 by winter flounder. This underutilization 

 may be related to prey size, burrowing depth, 

 defense or escape mechanisms, or a variety 

 of other factors (Main, 1985). For example, 

 there was limited predation on C. lacteus, a 

 major contributor to benthic biomass at sta- 

 tion NY6. This nonproportional consumption 

 or possible "avoidance" of this species is evi- 

 dent in the difference between the propor- 

 tional consumption and abundance levels at 

 this station (3.0% stomach volume vs. 45.3% 

 benthic biomass) and the strong negative K ( 

 Table 3); this difference at NY6 was fairly consistent 

 over the study period (Fig. 6). Proportional preda- 



Station NY6 



50 



40 

 30 

 20 

 10 



#/0.1 sq m 



4 - ' ' I >■ 



7 8 91011121 234567 8 91011121 2 3 4 5 6 7 8 91011121 23456 789 



I 86 I 87 I 88 I 89 I 



collection periods 



% Ireq occurrence 



# per square meter 



Station NY11 



#/0.1 sq m 



q i i r ix^ I I I I I I I I I I I I I i I i I I I I I I i xi ^ — i i i i i ; l^ I Q 



7 8 9101112 12 3 4 5 6 7 8 9101112 12 3 4 5 6 7 8 9101112 123456789 



I 86 I 87 I 88 I 89 



collection periods 



% freq occurrence 



# per square meter 



-1.15; 



tion or slight underutilization of this prey was evi- 

 dent at the other stations where it was less abun- 

 dant and K ranged from +0.08 to -0.40 (Table 3). 



