Evaluating the stock enhancement of eastern king prawns into a south-east Australian estuary

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Copyright: Setio, Christopher
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Abstract
Eastern king prawns (EKP, Penaeus plebejus) have high commercial and recreational value and thus are a target species for stock enhancement in eastern Australia. As the intermittent closure of the mouth can limit tidal flow and EKP recruitment, an ICOLL on the east coast of Victoria was selected for a trial EKP stocking project, which was undertaken between 2012-2015. Incorporating the responsible approach to stock enhancement, the trophic ecology and bioenergetic requirement of the target species, the suitability of the estuary for stock enhancement and the success of the trial release were investigated. First, the diet and trophic ecology of EKP (and opportunistically, school prawns; SP, Metapenaeus macleayi), were quantified. Gut content analysis revealed that bivalves, crustaceans and to a lesser extent detritus, were the dominant dietary items for both species. Similarly, stable isotope analysis indicated that both EKP and SP were generalist foragers. Bioenergetics modelling revealed the daily energy requirement for estuarine EKP was 217 J g-1 day-1. Prawn metabolic rate was significantly lower at 18'C than at 21'C and 24'C, meaning that prawns will grow slower in winter. After the trial stocking program, genetic analysis determined that over 50% of EKP caught after the first release were stocked individuals. The genetically identified prawns grew rapidly at ~16 mm total length per week, indicating ideal conditions for growth within the estuary. Survival of stocked EKP could not be determined, but was inferred from anecdotal reports of high catch rates post stocking. The suitability of the estuary for stocking was further supported by pre-release surveys of wild prawn densities, primary productivity estimates, and the distribution of seagrass habitat. Overall, this indicated that the trial stocking of EKP was successful, as stocked individuals were capable of surviving and growing post release and contributing to the local recreational fishery. This trial marine stocking program has created the appropriate protocols for the continuation of large scale marine stock enhancements in eastern Australia. Furthermore, this study emphasizes the importance of pre- and post-stocking assessments on both the target species for stocking and release location.
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Author(s)
Setio, Christopher
Supervisor(s)
Suthers, Iain
Smith, James
Taylor, Matthew
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Publication Year
2016
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Thesis
Degree Type
Masters Thesis
UNSW Faculty
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