PHABSIM modelling of Atlantic salmon spawning habitat in an upland stream: testing the influence of habitat suitability indices on model output

This paper reports the findings of research designed to assess the ability of PHABSIM to predict Atlantic salmon Salmo salar spawning habitat in the Girnock Burn, a tributary of the River Dee in northeast Scotland. It used an 18-year spawning data record to assess: (a) the ability of PHABSIM to predict between-year differences in the availability of habitat at the study site; (b) the ability of PHABSIM to predict patterns of relative suitability across the site; and (c) the influence of different Habitat Suitability Indices (HSIs) on the model's predictions with respect to (a) and (b).

Predictions of between-year and within-site habitat availability based on 'utilization' and 'preference' HSIs developed in the Dee catchment corresponded significantly (chi-squared and regression tests, P < 0.05) with the use of the site by spawning fish. However, predictions based on utilization HSIs developed in streams in southern England did not correspond significantly with patterns of site use. Results of the study indicate that PHABSIM is capable of predicting Atlantic salmon spawning habitat in upland streams such as the Girnock, but that the use of appropriate HSIs is critical. Copyright (c) 2005 John Wiley & Sons, Ltd.