Annual total mortality and population stucture of jackass morwong (Nemadactylus macropterus Bloch & Schneider) in eastren Australian waters

Abstract

Catch curves were analysed to estimate the annual total mortality of jackass morwong landed at the port of Eden between July 1976 and June 1979. The annual total mortality of females was lower in 1978-1979 than in the previous 2 years, reflecting the expansion of the trawl fishery in New South Wales to include previously unexploited deepwater grounds. Males were fully recruited to the commercially exploited population at an earlier age than females. It is suggested that the increased mortality in older males is due to an increase in natural mortality.