Abundance indices for main commercial fish species caught by trawl from the south-eastern Australian continental shelf from 1918 to 1957

Abstract

Per-haul records of catches by steam trawlers on the south-eastern Australian continental shelf from 1918 to 1957 were examined for the main commercial species tiger flathead (Neoplatycephalus richardsoni), jackass morwong (Nemadactylus macropterus), redfish (Centroberyx affinis), latchet (Pterygotrigla polyommata) and chinaman leatherjacket (Nelusetta ayraudi). Catch rates in weight per haul per species were standardised to annual indices of abundance using a log-linear model. Standardised annual index trends for flathead, latchet and leatherjacket indicate a strong to severe decline during the period covered by the data. All species showed seasonal patterns, but the peak season varied depending on the species. The distribution of standardised catch rate by area also differed greatly by species, and no single area showed consistent differences across all species. Day trawls caught more flathead, redfish and latchet, while night trawls caught more morwong and leatherjacket. Moon phase had less influence on catch rates than other factors. The correlation of annual index trends to a number of annual mean environmental factors was examined and no strong correlations were found.