Handle with care: an analysis of the effects of appendage damage on the growth and productivity of the southern rock lobster (Jasus edwardsii)

The capture, handling and release of lobsters during commercial fishing operations can damage appendages and reduce the exploitable biomass available to fishers as moulting lobsters expend energy resources regrowing limbs at the expense of increasing in size. To assess the effect of different types of injuries on the growth of juvenile male and female lobsters, a Bayesian hierarchical approach was taken to fit the parameters of the von Bertalanffy growth equation to mark-recapture observer data from southern areas of the Tasmanian southern rock lobster (TSRL) fishery in Australia. While the effect of handling damage on the growth of females could not be distinguished from zero, the impact on males was marked, with damage to an antennae or legs estimated to have a similar proportional impact on growth of 7% (0-16%, 95% CI) and 7% (0-14%, 95% CI) respectively. Damage to both antennae and legs had a greater proportional impact on growth of 40% (24-57%, 95% CI). Despite handling damage causing reductions in predicted growth, less than 6% of undersize male lobsters displayed these types of injuries. With an estimated 4.51 ± 0.08 million lobsters discarded annually between 2001 and 2010 from southern areas of the TSRL fishery, this led to a predicted annual lost productivity and profitability of 1.6 tonnes and $72,905 respectively. This was less than 1% of the total allowable catch and revenue of the fishery in 2010. This result highlights the effectiveness of management measures and biology of the species in reducing excessive amounts of handling damage.