Seasonal distribution patterns of fishes within the Bathurst Harbour estuary, southwestern Tasmania

Abstract

The distribution of fishes within the Bathurst Harbour estuary was surveyed by gillnet on five occasions and by seine on three occasions, between October 1988 and July 1989. Fish distributions did not noticeably change within the estuary in response to seasonal changes in salinity. A number of fishes were, however, possibly prevented from entering the estuary during February 1989 because of low oxygen concentrations then prevailing. The assemblage of Bathurst Harbour fishes collected by gill net was unusual in being dominated by sharks and skates, with all of the common species also being distributed in water depths >50 m along the continental shelf. Thus it has many characteristics typical of a deep water assemblage. Included amongst the Bathurst Harbour fishes was a previously unknown of species of skate which may be restricted to the estuary. By far the most common of the larger fishes was the white-spotted dogfish Squalus acanthias this species comprised 86% of the total gill net catch. Despite these large catches, a tagging study in which a very high proportion (25%) of tagged dogfish were recaptured indicated that the total population in the estuary was not exceptionally large, being in the order of only 2900 animals. Tagged dogfish roamed widely through the estuary.