In 1999/00, Southern bluefin tuna farming production will reach A$220 million. The industry is fully reliant on whole baitfish, predominantly pilchards, as the optimum feed to promote tuna growth in the sea pens. Unfortunately, because of Australian catch quotas on this resource, only a small proportion of the quantity required by industry can be sourced in Australia - the remainder of the requirements are sourced from overseas. For the continued success of the tuna farming industry stability in feed resources must be sustained.
Final report
The project provided nutritional profiles for all types of baitfish used for feed in the Southern Bluefin Tuna (SBT) (Thunnus maccoyii) Aquaculture Industry, as well as for the only available commercially produced compound feed and SBT. Included are values for amino acid and fatty acid profiles for most bait types and proximate analysis for all bait types.
The nutritional profiles have been determined by taking baitfish samples that coincided with major shipments of baitfish in the industry or landings of local pilchards. Weston Food Laboratories, Sydney, Australia undertook all analytical testing.
Often replicate samples were taken and provided to other projects. These included projects researching the development of NIR (Near Infra Red) technology that has the potential to provide a quick screening method for the proximate analysis of baitfish “2001/249 Aquafin CRC - SBT Aquaculture Subprogram: development and commercial evaluation of manufactured diets” and investigating the relationship of residues in the flesh of baitfish and wild caught and farmed SBT “2003/227 Aquafin CRC - SBT Aquaculture Subprogram: development and validation of baitfish sampling methods to address international residue standards for southern bluefin tuna (Thunnus maccoyii)”.
The baitfish profiles produced have been of significant value as they have heightened the understanding of nutrition in SBT farming. This has led to other projects including “2004/211 Aquafin CRC - FRDC SBT Aquaculture Subprogram: nutritional profiles of baitfish 3: effects of harvest and post-harvest processes on quality of local pilchards for feeding SBT” and “2000/221.20 Aquafin CRC - FRDC SBT Aquaculture Subprogram: quality and nutritional evaluation of baitfish used for tuna farming project 2000/221 (extension)”. Both of these projects will significantly enhance the understanding of baitfish feeds used in the SBT industry.
A direct result of this project has been the development of a feed optimisation program “Formu-Bait”. This software combines the current nutritional understanding of SBT, nutrition and industry feeding strategies with the baitfish database generated by this project.
As part of the original objectives the project sought to determine seasonal variability in the nutritional profiles of key baitfish. This was not achieved due to the seasonal nature of SBT farming (December – September) and the limited period over which most baitfish is purchased or caught. However, there appears to be a seasonal trend in the local caught pilchards (Sardinops neopilchardus) which shows a slight increase in fat content of pilchards caught during the summer/autumn months. This trend may be the result of up-wellings that occur in the lower Spencer Gulf and East Great Australian Bight during this time of year providing food to the pilchards.
To take this project further there is a need to test more SBT and baitfish to build on the current database, particularly where gaps exist or unexplained variability is high.
Keywords: Baitfish profiles, aquaculture, nutrition, SBT farming.
