Impact of lobster size on selectivity of traps for southern rock lobster (Jasus edwardsii)

Abstract

Most lobster fisheries are characterized by high exploitation rates. This has led to substantial declines in the size structures of the populations over time as larger lobsters have been removed. Although both scientists and fishers have suggested that size related hierarchies could impact on lobsters entering traps, the effect of the size change on the selectivity of lobster traps as a population's size structure changes has not been investigated. This paper demonstrates that larger lobsters affect the entrapment of smaller lobsters and that this behaviour affects the selectivity of lobster traps. Both spatial and temporal (within season) factors were found to affect the selectivity plots. Spatial differences in selectivity were attributed to the broader size range of larger lobsters found in regions of faster growth. Temporal differences were attributed to the decline in larger lobsters over the course of a season caused by exploitation. There are also differences in trap selectivity between the sexes.