Suitability indices for juvenile 0+ roach [rutilus rutilus (l.)] using point abundance sampling data

A habitat suitability model is derived for juvenile 0+ roach [ Rutilus rutilus (L.)] in the river Great Ouse (UK) using data collected by point abundance sampling by electrofishing. A total of 1718 point samples was used in the analysis. Of these, 392 contained juvenile roach. Polynomial equations describing habitat suitability are derived from depth, mean substratum particle diameter and water velocity data, and an index of plant cover suitability is described. Optimum conditions for roach are a depth of 1 m with a coarse (particle diameter 15–20 mm) substratum and negligible velocity, in the presence of floating and submerged broadleaved plant cover. The model is capable of discerning between null (fish absent) and non‐null (fish present) points in the original data set. It is shown that sampling effort may be reduced by approximately 60% without altering the model's predictions.