Food Resource Utilization By Five Species Of Benthic Feeding Fish In Passamaquoddy Bay, New Brunswick

摘要

Feeding relationships of various fish species, and their relationship to the composition of the surrounding sediments, were observed for one year at two sites in the lower Bay of Fundy region. The fishes were the ocean pout (Macrozoarces americanus), winter flounder (Pseudopleuronectes americanus), plaice (Hippoglossoides platessoides), cod (Gadus morhua) and witch flounder (Glyptocephalus cynoglossus). After reducing the size of the data matrix by removing redundant variables (prey items), interspecific diet overlap and the degree to which stomach contents reflect benthic composition were assessed using discriminant functions analysis. Variables were ranked by their power to discriminate among pairwise comparisons of groups: fish species and benthic samples. Many amphipods were utilized to a greater extent than their abundances in the sediments would suggest. Many annelids were underutilized. Each fish species has developed specialized feeding behaviours, digestion techniques and morphologies to segregate food resources. All species tend to increase prey intake at those places and times when benthic abundance of prey common to their diets increases. Visual predators (flounders) show different functional responses towards increased prey abundances than non-visual predators (ocean pout). In some cases availability is determined by prey size rather than prey abundance.;Only a few prey species show benthic density changes as a result of predation. Benthic populations may be held at an early successionary, highly productive stage by extreme physical conditions. Large fluctuations in temperature, salinity and current could provide a force regulating benthic species abundance that is at least as important as fish predation.