If the Midwest is to achieve its potential of 40,000 tonnes of annual finfish production in the longer term it initially needs incremental development. At the moment it is surrounded by large risks. In order to progress, some of these risks need to be fully identified and then removed, reduced, managed or mitigated. This project is needed to address the removal of those barriers to commercial development that have been identified during the current MFA project (eg parasites) and optimising some key inputs (larval and genetics) to production to improve the commercial viability of a larger scale industry
There is a need for a genetic management strategy to ensure that the captive broodstock comprise a genetically diverse population in order to avoid inbreeding and to provide good opportunities for future genetic selection. There is also the need to more fully understand what genetic variation exists in wild yellowtail kingfish from within WA to both ensure that broodstock populations are representative of this diversity and to make management decisions regarding integration into national breeding programs.
High incidences of malformations continue to impact heavily on the price of juvenile kingfish. There is a need therefore, to reduce the incidence of such malformations to reduce the cost of juvenile production and improve the quality of fish being put to sea.
Sea-caged yellowtail kingfish in Western Australia have a high prevalence of the myxozoan parasite Unicapsula seriolae. It has been recorded in the Jurien Bay fish in 2008/9 and has been monitored closely from development in the current MFA yellowtail kingfish project. This parasite results in myoliquefaction in the same species of fish in Queensland. Its impact on a potential yellowtail kingfish commercial aquaculture industry in WA needs to be assessed and management practices developed and implemented to reduce its impact.
Final report
Sub-Project 1: Genetics
DNA analyses were used to develop a mating strategy to avoid inbreeding among the limited number of existing captive broodstock in WA. A genetic management workshop was carried out in with ACAAR and WA Industry and used to inform attendees about basic genetic management principles and to collect information relevant to the formulation of the strategy. A genetic management database for tracking fish, collection of water quality data, recording treatments, pedigrees, relatedness and fish traits was developed and tested. The same database has been further enhanced and rolled out to ACAAR and two barramundi hatcheries (Project 2009/730) offering a simple but effective genetic management tool for both of these species.
Sub-Project 2: Larviculture
Our study comparing different rotifer feeding strategies demonstrated that up to 65% fewer rotifers can be used in the production of juvenile YTK than are currently being used in commercial hatcheries, without any negative impact on growth or survival. This is the result of efficient prey capture at low prey densities, even from a young age. This reduction in rotifer usage translates directly to the same percentage reduction in rotifer operating costs. We were unable to determine whether these different strategies had an effect on larval malformation rates, due to the small size of the larvae at the end of the rotifer feeding phase. The results of this research are now being implemented at ACAAR and a manuscript describing this research has been submitted to the ISI Journal, Aquaculture Research. Detailed biochemical composition analyses were performed on rotifers and Artemia enriched on various diets and a blend of diets used in the commercial hatchery production of cobia. These analyses revealed some significant differences in certain aspects of the nutritional composition of both live feed types.
