The ecology of trout within the Lough Neagh catchment

Abstract

The response of biological indicators to human induced stress will form an integral part of the future monitoring of European rivers. The brown trout Salmo trutta L. is part of one group of indictors that will be used to assess the ecological health of freshwaters and to identify areas in need of rehabilitation. In order to undertake appropriate corrective measures within these areas, an understanding of the possible pathways of degradation from different land use factors is required.

This study examines the impact of different land use on trout populations within
the Lough Neagh catchment area as well as adding to the current knowledge of trout
migratory strategies within the area.

Physical habitat, water chemistry, invertebrate and trout populations were sampled across 1 o different land use types, within four areas of the Lough Neagh catchment. Significant differences in stream habitat were observed across several land use types with artificial and complex cultivation areas consistently showing signs of degradation. Land use was found to be a good descriptor of differences in stream habitat. Invertebrate communities were also found to change with land use with the lowest BMWP and ASPT scores found within agricultural areas.

Trout densities were reduced on a site specific scale along an increasing eutrophic gradient, however significant differences were observed on a catchment wide scale through analysis of historical data. Trout growth was correlated to increasing water depth, % boulder and drifting Ephemeroptera, Plecoptera and Trichoptera taxa. Migratory trout growth differed significantly between catchments, with evidence presented of a potential link between stream size and migration timing.

Date of Award	Sept 2006
Original language	English