Sewage sludge disposal and winter flounder, red hake, and american lobster feeding in the New York Bight

Abstract

Little is known of the effects of sewage sludge disposal on fish and shellfish feeding. This paper presents the results of a 39-month study on the effects of sewage sludge disposal and its abatement on feeding of three species in the New York Bight. Feeding variables were measured in winter flounder, red hake and American lobster at three sites along a gradient of sludge influence. Post-abatement changes in benthic habitats included reduced sediment total organic carbon (TOC) and metal contamination, and increased summer bottom water dissolved oxygen (DO) and changes in the abundances of some benthic infaunal species at the study sites. Statistically significant diet changes were only evident in winter flounder, however. The limited sample sizes and relatively high variability of the results for red hake and lobster gave the tests on the percentage of empty stomachs a relatively low power (1− β = < 0·20) for detection of change, or greater than 80% chance of incorrectly accepting the null hypothesis at a 95% confidence limit (and detectable effect size) even with percentage of empty stomach changes of up to 52% for these two species. There were, however, changes in the frequency of occurrence of certain artifacts or minor, pollution-sensitive prey in the diets that can be associated with sludge disposal abatement. The importance of these changes to predator health was not assessed.