PIRSA Aquaculture have indicated that they intend to develop a number of new aquaculture zones around the state over the next 5 years as well as revisit early assumptions of carrying capacity estimates developed in Innovative Solutions 1, in order to meet the anticipated expansion of the aquaculture industry within South Australia. This expansion is necessary to meet SA’s target of $2 billion in seafood production by 2015. It is also essential that PIRSA Aquaculture is prepared for successful propagation of southern bluefin tuna, which could see the farmed biomass of this species increase significantly in a few years, particularly in Spencer Gulf where existing aquaculture infrastructure and support services are in place.

The ability to obtain accurate estimates of spatial and temporal variability in the cycling of carbon and other macro-nutrients through the ecosystems in Spencer Gulf will provide important information about potential risks and impacts of increased aquaculture activities in the Gulf. This need will be met through the development of calibrated hydrodynamic and bio-geochemical models for Spencer Gulf that will also determine the carrying capacity of aquaculture areas, including the concurrent use of both supplementary and non-supplementary fed organisms within each area. Further, the development of strategies for long-term performance monitoring, management and mitigation are needed for the aquaculture areas in Spencer Gulf. These outcomes will further justify the South Australian government’s approach to sustainable aquaculture development as directed by the Aquaculture Act 2001.

The stated limits in the ability to deliver the above for other areas (e.g. shelf waters off Ceduna) or species (e.g. scallops) by the researchers will aid PIRSA Aquaculture to determine the future resource requirements for getting the other areas of South Australia up to the policy and regulatory standards set by this work in Spencer Gulf.

Ultimately, the need is to improve the quality of the product at this time of year when mature males occur and when sea temperatures reach their peak. If mature males are shown to contribute significantly to product quality issues at this time, then remedial measures can be investigated which are proportional to the scale of the problem.

Information on the extent of the impacts of maturation and/or harvest stress on product quality of YTK will help all involved in growing, buying and selling YTK in domestic and overseas markets.

Yellowtail Kingfish culture is a rapidly expanding industry in Australia, particularly in rural South Australia, where it is driving the increase in the ‘other’ category of aquaculture production from ~1100 tonnes valued at ~$9 million in 2002-03 to 2000 tonnes and $17 million in 2004-05 (ABARE, 2006). Regarding future production, CST alone are projecting an increase in annual production towards 8,000 T by 2015.

CST is the largest producer of Yellowtail Kingfish in Australia having produced over 1.25 M juveniles in 2007. The company operates two Yellowtail Kingfish hatcheries at Arno Bay and Port Augusta. The production of quality larvae from hatcheries underpins the production of farmed fish and low survival and high levels of malformations significantly increase costs.

Survival of Yellowtail Kingfish juveniles in Australian marine hatcheries is very low in comparison to many other marine species such as sea bass and bream produced in larger more mature industries, for example in Europe. Of particular note, several skeletal malformations have been reported in Australia and New Zealand, although few are well documented (Yellowtail Kingfish, Cobcroft et al., 2004).

There is also high variability in hatchery survival rates and the rate and severity of deformities among production runs and commercial hatcheries.

By way of illustration, the direct benefit to Clean Seas Tuna Ltd. of reducing malformations in Yellowtail Kingfish is estimated to be $1 million p.a. In this example a reduction in malformations from 40% to 20% (on 2.0 M juveniles before quality grading) could produce a further 400,000 good quality juveniles @ $2.50 (market value) = $1,000,000.

Controlling flukes of YTK is a major cost for producers, and the industry has identified improving the treatment of flukes as one of the top research priorities. Currently, the industry bathes fluke-infested YTK in hydrogen peroxide. Although this approach is currently efficacious, it is also costly, labour-intensive, and stressful for fish. An option to reduce the need to bathe frequently is to use in-feed therapeutic agents to kill or remove flukes. This project aims to develop palatable feeds containing medications that will significantly reduce burdens of flukes.

Changing bio-fouled nets is another costly practice for the industry. Antifoulants have the potential to not only reduce the frequency and cost of net-changing due to the need to maintain good water flow bringing dissolved oxygen to the caged fish, but also to potentially reduce the numbers of fluke eggs entangling on the nets, and therefore further reduce the numbers of infective fluke larvae settling on YTK within cages. The optimum compound to use from an assessment of three will be identified.

Commercial YTK may have experienced slower growth at Fitzgerald Bay than at Arno Bay; the cause is suspected to be due the higher salinity (39-42 ppt at Fitzgerald Bay, compared with 37 ppt at Arno Bay). It needs to be confirmed experimentally whether increased salinity slows growth, first in summer and, if not, then in winter.

Health issues affecting hatchery-reared, larval SBT are presently unknown. Before production begins, the development of health protocols and a surveillance program is required, as well as the collection of archival samples of larvae for future investigations. These investigations not only ensure the biosecurity of the hatchery but also the sea-based growout stage, whether associated with hatchery-produced or wild-caught stock. This project will also allocate a small amount of funds for early disease testing, if required.