Post harvest weight loss has important implications for abalone quota management

Regulations forming part of the abalone quota management system in Victoria, Australia, require that abalone processors notify fisheries authorities of quantities of abalone consigned from commercial divers within 25 hours of landing. The regulations also require that the abalone are to be landed whole in the shell, and transported and stored in sealed bins until one half hour after official notification. Whilst the bins cannot be opened prior to notification, the 25 hour limit for notification provides a window of opportunity to make potential gains through weight loss in those abalone destined for canning. This arises because notified weights, rather than weights estimated upon landing, are used to decrement the quota allocations of individual divers. I investigated the potential for post-harvest weight loss by subjecting abalone to three experimental treatments selected to simulate a range of possible transport and storage regimes. My results demonstrated that substantial weight loss can occur in whole abalone during both ambient and refrigerated storage. Loss of weight in abalone during storage results from the release of water and body fluid associated with physiological responses to hypoxic stress caused by exposure to air. In Victoria, about 60% of the landed catch is used to produce canned product. At present, weight losses during storage are not accounted for in setting the Total Allowable Catch and divers supplying abalone for canning have to harvest more abalone to achieve their quotas than those supplying abalone for live export. Losses in weight of 10-20% observed during this study equate to 350,000-700,000 more abalone harvested than if beach weights were deducted from quotas. These additional quantities of abalone harvested may exceed desired fishing mortalities for long-term population sustainability.