Seafood CRC: improving hatchery production of Yellowtail Kingfish larvae and fingerlings
CST is moving to the capacity for a 5,000 ton per annum sustainable YTK business by 2020. To underpin this growth in the YTK industry it is critical that the hatchery production efficiency and quality of fingerlings produced are improved.
This project will direct investment in skilled personnel and resources to increase our understanding of critical factors that can be manipulated for improved yield of YTK juveniles and lower production costs by refined culture conditions to achieve reliably higher survival, higher swimbladder inflation rate and lower incidence of skeletal deformities.
The project fits within the Seafood CRC outputs and milestones, as follows, toward the outcome of a 'substantial increase in the production and profitability of selected wild-harvest and aquaculture species'.
1.1 (Output) Technically verified new aquaculture production systems on a commercial scale
1.1.2 (Milestone) Key researchable constraints identified and characterised in at least two new production systems
1.1.3 (Milestone) Key researchable constraints successfully addressed in at least two new production systems
Three significant issues were identified in YTK larval rearing over the last 3 years that present bottlenecks to hatchery production efficiency. These include:
1. low survival (potentially linked to high microbial load in live feeds and larval cultures, sinking of older larvae, variable temperature which is constrained by ‘outside’ rearing conditions under ambient natural sunlight)
2. low swimbladder inflation rates (associated with changed husbandry conditions; upwelling, mister fans, skimming efficiency, algae pastes, larval health/nutrition)
3. high rates of jaw deformity (potentially linked to quality and quantity of enriched rotifer and Artemia diets, temperature)
The project addresses all three issues, with a focus on applying results from previous research at medium and commercial-scales (light intensity and quality, and temperature, live feed regimes) and investigating larval nutrition and photoperiod at a small-scale.
Final report
Clean Seas Tuna is the largest commercial hatchery producer of Yellowtail Kingfish fingerlings in Australia. Following three years of research (2007-2010) into larval rearing issues, the company still experienced variability in results between the two hatcheries, Port Augusta and Arno Bay, between runs within hatcheries, and between individually stocked larval tanks (even those stocked from the same egg batch). 2009 was particularly challenging compared to the previous two years with an increase in skeletal malformations (jaw deformity from 20-25% to > 50%), decrease in survival (from >10% to 8%), and decrease in swimbladder inflation (from 99% to 80%). This 1 year project built on and applied, at a commercial scale, the results of the previous projects (SfCRC 2007/718 and 2009/749). The project was designed to support improved Standard Operating Procedures and test promising alternative rearing conditions, identified in previous research (especially temperature and artificial light), at a medium-scale in Arno Bay and Proof-of-Concept (commercial-scale) in both hatcheries. Funding was requested to invest in skilled personnel, upgrade systems, support key national collaboration, and provide operational costs at partner organisations.
Seafood CRC: Commercial production of all-female reproductively sterile triploid Giant Tiger prawns (Penaeus monodon): Assessing their commercial performance in ponds.
The Australian prawn industry needs a mechanism by which to confer genetic protection of seedstock with elite genotypes so that their commercial benefits can be made available to the entire domestic industry through the sale of elite seedstock for on-growing. To-date triploidy is the only available technology that is near commercialisation that provides a high level of genetic protection through reproductive sterility.
Triploidy has the added benefit of resulting in female populations, with females naturally growing larger than males. This attribute should provide further improvements on harvest yield beyond the performance provided from the elite genotypes alone. If this project demonstrates that total harvest yields are substantially improved through stocking triploids as predicted, triploid induction technologies will be of direct benefit to (and can be utilised by) the entire Australian industry as wild spawned females are also larger than males. This provides direct benefits to the industry independent of accessing the elite genotypes being produced by the four largest Australian prawn producers, providing immediate benefits for any Australian farm or hatchery producing seedstock.
Final report
Several Australian companies currently have breeding programs producing domesticated and selective-bred Penaeus monodon lines. The most advanced of these lines have demonstrated high commercial pond performance over several generations. However, there is a risk for the breeding program companies, due to on-sale or on-rearing of their selected postlarvae. To avoid this problem, genetic protection for the selectively bred prawns is required; however, to-date there is no commercial method for fail-proof genetic protection of prawns. Triploid induction is the only methodology that has been trialled experimentally that shows promise of genetic protection in prawns. However, there are limited reports of triploid induction in Black Tiger Prawns and no studies have reared the larvae through to harvest age and conducted rigorous performance measurements for this species.
This project aimed to develop a technique that would be suitable for commercial triploid induction (which gives each individual an extra set of their own chromosomes; a process that occurs sporadically in nature) of whole spawnings of the Giant Tiger Prawn. A methodology was developed to induce whole spawn triploidy with temperature and chemical shocks. However, hatch rates from this system were consistently low. Despite this a chemical induced triploid family with a high induction rate and reasonable larval survival was produced at a commercial hatchery, allowing rigorous tank-based performance assessments to be carried out.
The overall performance of triploids was comparable to other penaeid prawn species with some exceptions. In triploids, survival was lower, and females were significantly larger. Furthermore, there were more males than females with a 1:1.625 sex ratio and reproductive age triploids were unable to produce viable offspring. This demonstrates that triploidy would provide the industry with a method of genetic protection for Black Tiger Prawns, however significant challenges in maintaining high hatch rates, survival rates and induction rates of the triploids when inducing whole spawnings on a commercial scale still remain.