Factors influencing individual movements and behaviours of invasive European barbel Barbus barbus in a regulated river

Abstract

Riverine fish are often adversely affected by impoundments that reduce longitudinal connectivity and impede movements, while river fishery performance is often enhanced by introductions of non-indigenous fishes that diversify angling opportunities. The influence of factors (including impoundment) on the movements of European barbel Barbus barbus, a fish frequently introduced for angling, was tested in the continuous reach of the lower River Teme and Severn, western England. Following capture by electric fishing and angling, the movements of 18 fish were followed for 12 months using acoustic telemetry. Weirs at the upstream end of both river reaches impeded fish movements; only three fish traversed the Teme weir and no fish traversed the Severn weir. Net movements were mainly upstream in spring and downstream in autumn, and the daily movements of fish were asynchronous between individuals. Total (home) ranges varied considerably between individuals; those of fish initially captured by angling were significantly smaller than those captured by electric fishing. This potentially relates to fish with smaller total ranges being more vulnerable to angling via higher spatial encounters. The results reveal considerable individual variation in the movement of B. barbus and emphasises how river regulation can impact the dispersal and behaviour of river fishes.