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Fishery Bulletin 92(3), 1994 



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collection period 



stomach volume 



benthic biomass 



Figure 6 



Trends in the percent contribution of the rhynchocoel 

 Cerebratulus lacteus to the total stomach volume of winter floun- 

 der, Pleuronectes americanus, compared to the rhynchocoel's 

 percentage contribution to total benthic macrofaunal biomass 

 at NY6, the station most affected by sewage sludge disposal 

 and its cessation, in the New York Bight apex. 



The limited predation on C. lacteus could be re- 

 lated to its possession of defensive toxins in its tis- 

 sues or to secretion of mucus that is strongly acidic, 

 both of which can be offensive to potential predators 

 (Kern, 1985; McDermott and Roe, 1985). Paradoxi- 

 cally, rhynchocoels are collected for fish bait in some 

 areas and eaten by other fishes. It is possible, how- 

 ever, that this rhynchocoel's large size (>100 cm in 

 length and >2 cm in width; Gosner, 1971), not its 

 reported toxicity, is responsible for its limited use as 

 prey for the small-mouthed winter flounder. 



The underutilization of the small bivalve mollusc 

 N. proximo (Table 3) is probably the result of its lack 

 of availability as this species burrows into the sedi- 

 ment. The other molluscs common in the area, such 

 as P. morrhuanus,A. islandica, Ilyanassa trivittata, 

 and Ensis directus, are probably either too large or 

 deeply buried to be suitable prey for winter floun- 

 der. However, N. proximo, as well as these other 

 molluscs, except P. morrhuanus, were noted as prey 

 in the diets of winter flounder elsewhere (Kurtz, 

 1975; Gilbert and Suchow, 1977; Klein-MacPhee, 

 1978; MacDonald et al., 1982; Worobec, 1982). The 

 molluscan contribution to winter flounder diets in 

 Narragansett Bay, Rhode Island, was also considered 

 negligible (Bharadwaj, 1988). 



Cessation of sewage sludge disposal 



The cessation of sewage sludge disposal was expected 

 to result in a substantial change in abundance of dis- 



posal-sensitive species in the benthic 

 macrofaunal community. Any macrofaunal 

 changes because of cessation were expected 

 to be reflected in some predation variables 

 (Spies, 1984; Cross et al., 1985; Environmen- 

 tal Processes Division, 1988). However, the 

 only significant changes in the benthic com- 

 munity detected after cessation from 1987 to 

 1990 were in the overall abundance of a few 

 pollution-tolerant or pollution-sensitive taxa, 

 such as the polychaete Capitella sp. or am- 

 phipods at station NY6, nearest to the former 

 disposal area. The abundance of other domi- 

 nant benthic species at NY6, such as P. 

 affinis, N. incisa, and C. americanus, did not 

 change to any significant degree (Reid et al., 

 in press). 



The pollution-tolerant Capitella sp. has 

 been a consistent, but variably abundant 

 (hundreds to tens of thousands of individu- 

 als/m 2 ), member of the degraded benthic com- 

 munity at station NY6 since at least the early 

 1970s (Caracciola and Steimle, 1983). Its 

 density in the macrofauna declined drasti- 

 cally (<100 individuals/m 2 ) after the cessa- 

 tion of sewage sludge disposal (Reid et al., 1991). 

 Predation by winter flounder on this prey is prob- 

 ably related to the response of Capitella sp. to cessa- 

 tion of disposal. 



There were increases in abundance of contami- 

 nant-sensitive amphipods, especially Photis pollex 

 and U. irrorata, at station NY6 after disposal abate- 

 ment began in 1987. Although contributions of am- 

 phipods to winter flounder diets were generally less 

 than V'/r of total stomach volumes (and thus not in- 

 cluded in Table 3), numerical increases in amphipod 

 abundance in the macrofaunal community coincided 

 with increases in their frequency of occurrence in 

 winter flounder stomachs. The general increase in 

 the numerical abundance of one amphipod, U. 

 irrorata, in benthic samples at NY6, especially after 

 cessation, was accompanied by a corresponding in- 

 crease in their occurrence in winter flounder stom- 

 achs (Fig. 5). However, a similar predation relation- 

 ship for this prey was somewhat evident at station 

 NYU, which was minimally affected by sludge dis- 

 posal and cessation (Fig. 5). At both stations, the fre- 

 quency of occurrence off/, irrorata in the diets closely 

 paralleled seasonal (winter-spring) peaks in abun- 

 dance, including reduced predation during an appar- 

 ently poor recruitment year at NY11 in 1988 (Fig. 

 5). If the effects of the sludge were more general and 

 included some effect at NYU, the pattern of preda- 

 tion on this species, which increased in abundance 

 after cessation, could be associated with this cessation. 



