Habitat evaluation as a fisheries management tool

Abstract

The application, rationale and process of habitat evaluation methods are discussed in the context of present day fisheries management. The need to consider habitat features at site and catchment level is stressed.Development of habitat evaluation techniques for assessing brown trout habitat in Welsh streams is reported, and examples of these approaches are given: qualitative (visual assessment), semi-quantitative (a combination of subjective and quantitative measurements) and quantitative (measurements on transect system). Habitat attribute-fish population models were based on functional linear regressions and multiple regression (for the quantitative method). Quantitative models explained up to 80% of the variance in abundance of medium sized (10-20cm) trout in hard water (>25mgI-' CaCO,), but were less effective when data from soft waters were included. Testing of the qualitative and semi-quantitative methods on independent data demonstrated that the latter was more effective in predicting habitat quality.Survey costs varied considerably but, although the more precise methods were more costly per site. they were the most cost-effective because fewer sites were required for a given level of precision.The problems associated with soft-water sites are discussed in terms of factors affecting site carrying capacity; and selection of methods is briefly considered in the light of current management practise.

Analyse des modèles de prédiction des populations de salmonidés en rivière

“…channel morphology/flow conditions and instream habitat) and the larger-scale catchment attributes such as geomorphology, topography, land-use and climate (MILNER et al, 1985).…”

“…For this exercise, the source of variables (as described by MILNER et al, 1985) was subdivided to differentiate between variables pertaining to the following catégories :…”

“…Thèse models form the basis of the latest version of HABSCORE, a system which enables prédictions of salmonid abundance to be made from information on stream habitat features. An early version of HABSCORE is in operational use in the Welsh Région of the National Rivers Authority (NRA) (MILNER et al, 1985 ;WINSTONE, 1993) where it is proving to be of practical value.…”

Le développement des modèles d'habitat pour les salmonidés d'eau courante et leur application à la gestion piscicole

“…The potential applications of fisheries habitat models fall into the areas of enhancement, conservation and impact assessment (MILNER et al, 1985). Their potential has been demonstrated by the routine use of the salmonid fishery management tool HABSCORE (MILNER et al, 1985 ;NRA, 1991).…”

“…Their potential has been demonstrated by the routine use of the salmonid fishery management tool HABSCORE (MILNER et al, 1985 ;NRA, 1991). This is a System which (in its original form) facilitated the évaluation of salmonid stream habitat in upland streams in Wales.…”