Effects of chronic bottom fishing on the benthic epifauna and diets of demersal fishes on northern Georges Bank

摘要

Feeding by demersal fishes on benthic invertebrates constitutes an important link between fishery resources and continental shelf habitats. However, concurrent sampling of demersal fish diets and benthic invertebrate prey fields has been limited, particularly in relation to chronic bottom fishing disturbance on continental shelves worldwide. Here, we quantified differences in the epibenthic invertebrate and fish communities between sites with contrasting levels of disturbance from mobile bottom fishing gear for 2 gravel regions of Georges Bank in the northwest Atlantic. The main objectives were to compare a suite of biological indices for epibenthic invertebrates, demersal fishes, and fish diets across year and level of fishing disturbance. The fishes selected for diet comparisons included winter skate Leucoraja ocellata, little skate L. eri-nacea, Atlantic cod Gadus morhua, haddock Melanogrammus aeglefinus, winter flounder Pseudopleuronectes americanus, and longhorn sculpin Myoxocephalus octodecemspinosus. Three baseline benthic epifaunal indices, species richness, abundance (no. l~(-1)), and biomass (g l~(-1)), were lower in the heavily fished areas; however, evenness was higher in these areas. The lengths of haddock, Atlantic cod, and winter flounder tended to be larger at the undisturbed sites. Fish stomach contents differed significantly among habitats for 3 benthivores: haddock, winter flounder, and longhorn sculpin; diets were more highly correlated with the benthic fauna within than among sites, which indicated site-specific feeding. In several cases, prey that contributed to the diet dissimilarity between sites were benthic epifauna most sensitive to the impact of bottom fishing disturbance; thus, the availability of epibenthic prey was determined by this disturbance.