Behaviour of two small pelagic and demersal fish species in diverse hydraulic environments

Abstract

<jats:title>ABSTRACT</jats:title><jats:p>Increased hydraulic diversity could be a means to promote fish diversity in rivers, but little is known of the behaviour of fish in hydraulic environments. This study concerns the behaviour of two species of small native Australian freshwater fish in variable hydraulic environments and ecological habit, with regard for (a) whether the apparent differences in swimming ability are reflected in the behaviour of the species and (b) the influence of changing hydraulic conditions on their patterns of use. An artificial channel was constructed with three levels of discharge, and fish were allowed to swim freely for 3 h without human interference. Their movements and habitat choices reflected their swimming ability and ecological habit, in that the stronger swimming, pelagic common galaxias (<jats:italic>Galaxias maculatus</jats:italic>) spent most time cruising in the open channel, preferring the turbulent inflow, and the demersal flat‐headed gudgeon (<jats:italic>Philypnodon grandiceps</jats:italic>) remained in the shelter of boulders. In effect, the galaxias changed their behaviour with changes in hydraulic conditions, while the gudgeons continued to use their preferred habitat. This study, therefore, provides support for the use of hydraulic diversity as a tool to foster fish diversity. Copyright © 2010 John Wiley &amp; Sons, Ltd.</jats:p>