Biological modeling of translocation as a management tool for a rock lobster fishery

Translocation is a form of sea ranching and involves shifting animals between regions to increase yield or to address sustainability issues. We used a sex and size structured model with yearly time steps to examine the use of translocation for management of the Tasmanian rock lobster (Jasus edwardsii) fishery, which is a fishery characterized by spatial heterogeneity in biology and depletion through fishing. Cohorts of undersize lobsters were translocated from four sites of origin to four release sites to explore outcomes under a range of growth rates. Results of translocations were contrasted against estimated yield and egg production if the lobsters had been left at their original site. Gains in yield of greater than 100% of existing yield appear possible through many scenarios, although gains were largest when distances between sites were greatest (from SW to NW Tasmania). Short-distance translocations from deep to shallow water have been proposed to alter market traits of lobsters, but gains in yield from this type of operation appear trivial. Egg production was increased at the release site for all scenarios, indicating that translocation could complement the current policy of rebuilding northern egg production. Translocation appears to offer an alternative management option for increasing yield and could be integrated with other spatial management tools such as regional size limits.