A methodology to develop aquaculture-based release strategies with an application to Metapenaeus dalli in the Swan-Canning Estuary: the Survival-Maximisation-at-Release Tool (SMART)

Abstract

Aquaculture-based enhancement, a method of releasing cultured organisms into the wild to boost fishery productivity, is becoming increasingly popular as a management option for restoring depleted fish stocks and increasing fishery yields. In the first section of this Thesis, I review and synthesise how the effectiveness of aquaculture-based enhancements can be optimised to maximise survival of released individuals. Two specific areas were identified that have a major influence on the short-term survival of released animals (i) “training” or acclimation in the hatchery to conditions in natural systems, e.g. habitats, water flows, natural (live) food and the smell and sight of predators through predator avoidance training and (ii) the development of a sound release strategy, involving the selection of site, time and size at release. The objective of the second section of this Thesis was to create a tool to inform the development of an optimal release strategy, by evaluating site selection and time of release for the release of post-larval Western School Prawns Metapenaeus dalli in the Swan-Canning Estuary. This was achieved by developing the Survival-Maximisation-At-Release-Tool (SMART), a quantitative tool that collated factors and variables considered to influence the survival of released M. dalli at potential sites around the estuary to determine a SMART score (0-100) for each potential release site and time (Month, Year, Day/Night). Statistical analyses on the resultant SMART scores determined that region of release was the most influential factor for the survival of released M. dalli, followed by year and then month. Due to the wide range of values for the salinity variable and sediment composition and predation factors among sites and time, these had the most influence on overall SMART score. Across the 16 nearshore sites sampled in five consecutive months in each of three years, the optimal site of release was at Deep Water Point in the Lower Canning Estuary during the night in January 2014. Recommendations for future improvements to the SMART methodology for releases of M. dalli were identified and mechanisms for adapting this tool for its application to other species and aquatic ecosystems are discussed. The SMART provides output that can be readily conveyed to diverse audiences (i.e. fishers, researchers, managers and the community) to enhance discussions on optimal release strategies