Space-time variation in catchability of southern rock lobster Jasus edwardsii in Tasmania explained by environmental, physiological and density-dependent processes

Abstract

Aseasonal catchability model for the rock lobster Jasus edwardsii, which had been developed previously for a population in a scientific reserve,was applied to catchability estimates over several years in northern and southern fishing regions off Tasmania, Australia. Catchability was estimated from commercial catch and effort data and fishery-independent estimates of exploitation rates. The seasonal catchability models describe the effects of water temperature, moulting and mating on catchability. They suggest that similar environmental and physiological processes underpin seasonal catchability in the two regions of the fishery, but that the relative importance of these factors varies considerably between the two regions. Physiological processes dominate the pattern of catchability in the north while water temperature contributes significantly to the model only in the south. Interannual variation in relative catchability was correlated with density-dependent processes. Full models described 72% of the total variation in catchability over 6 years in the south and 80% of the total variation over 4 years in the north.