Lake Huron Fish Community Structure Based on Gill-Net Catches Corrected for Selectivity and Encounter Probability

Abstract

This paper describes the depth distributions and numeric abundance of fishes in the Canadian waters of Lake Huron based upon size‐corrected results of experimental netting from 1958 through 1968. Gill‐net catches were corrected for encounter probabilities based on the positive correlation between fish size and swimming speed and for retention probability offish of different sizes once they encounter the net. A 3‐parameter gamma function was used to fit net‐selectivity curves for 13 Great Lakes species. Comparison of raw with corrected catches for Georgian Bay showed that the former exaggerated the relative abundance of deep‐water coregonines Coregonus spp. in the deepest strata and overrepresented the abundance of yellow perch Perca flavescens and lake chub Couesius plumbeus in the shallowest waters. Corrections resulted in status changes for several species that are major segments of the fish community. Nearly two decades after the collapse of the top‐level native piscivores, Georgian Bay retained much of the character of the fish fauna prevailing before establishment of exotic species. Deep‐water coregonines dominated the community at depths below 50 m. The main basin and North Channel supported major populations of rainbow smelt Osmerus mordax and alewives Alosa pseudoharengus; rainbow smelt abundance increased with depth. Deep‐water coregonines formed a substantial proportion of the fauna in all basins of the lake, Smaller benthic and littoral‐zone species were well represented in the shallower areas (less than 20 m deep) and were gradually dominated by rainbow smelt, alewives, and coregonines as depth increased. The three basins differed in fish species composition to a greater extent than would be predicted on the basis of their bathymetries. None of the larger species of piscivores characteristic of North American oligotrophic lakes were present in large numbers during the term of this study.

Composition, abundance and diversity of the Family Cichlidae in Oyan Dam, Ogun State, Nigeria

“…The feeding habit of the fish (piscivorous) could be responsible for its size. Some researchers have used fish size to estimate the relative probability that fish of various sizes will encounter the nets (Rudstam et al 1984;Spangler and Collins 1992). Comparatively, the food consumed by the populations of H. fasciatus in Tarkwa bay and the Lagos lagoon in Nigeria (Ugwumba 1988) consisted principally of fish.…”

Development of a fish-based index of biotic integrity (FIBI) to assess the quality of Bandama River in Côte d’Ivoire

“…Nets were set overnight (5.00 p.m-7.00 a.m) and during the following day (7.00 a.m-12.00 p.m). Indeed, gill-net selectivity depends on the probability that the fish meets the net and the probability that the fish was caught and retained in the net (a function of the circumference of the fish's head and of the mesh size of the gill-net) (Spangler and Collins, 1992). Many fish assemblage descriptors were considered as possible index metrics.…”

Lack of size selectivity for paddlefish captured in hobbled gillnets

“…Similarly, the EFL-girth relation for 58 preseason males (r 2 = 0.74; P < 0.001) was used to predict girth measurements for 65 other preseason males. For many species, maximum gillnet selectivity corresponds to G:P ratios centered around 1.1-1.4 (e.g., Spangler and Collins, 1992;Van Den Avyle et al, 1995) and some authors have concluded that the optimum girth is about 1.25× the mesh perimeter (e.g., Hamley, 1980). We created frequency-distributions of G:P ratios in each mesh to see whether the ratios fell within expected ranges.…”