Effects of sewage effluent discharge on the abundance, condition and mortality of hulafish, Trachinops taeniatus (Plesiopidae)

The effects of sewage effluent on the abundance, condition (length and repr oduction) and mortality of hulafish Trachinops taeniatus were investigated at multiple outfall and control locations on the central coast of New South Wales, Australia. Underwater Visual surveys found consistently fewer T. ta eniatus at locations where sewage was discharged compared to control locati ons. The condition of T. taeniatus was investigated by comparing mean lengt h and reproductive indices of fish from two outfall and two control locatio ns. Fish from the largest outfall location were significantly smaller in co mparison with fish from control locations. Gravid female fish from outfall locations had similar gonadosomatic indices but a significantly greater num ber of eggs and smaller size of eggs in comparison with fish from control l ocations. Mortality of T. taeniatus was investigated during 2-week, in situ , caging experiments at multiple locations and times and 80% of fish surviv ed, although mortalities of up to 73% per cage were recorded at one sewage outfall. T. taeniatus may be a suitable environmental indicator species of sewage pollution. (C) 1999 Elsevier Science Ltd. All rights reserved.