We have demonstrated that oyster characteristics deemed valuable by industry can be improved by selective breeding. We and industry are convinced that substantial performance increases for commercial lines are achievable.
Thus far we have concentrated our efforts on a single trait (growth), but we have a number of family lines which permit the improvement of several traits simultaneously. We plan to continue selecting for increased growth rate and combine these advances with other desirable traits such as high meat yield and irradication of the deleterious curl-back trait. This will yield a much improved commercial product.
Modifications to our existing protocols need to be trialed to see whether substantial gains in time and savings of funds are possible in the development of a long-term breeding strategy for broodstock improvement. We need to:

1. continue the breeding program through at least three more generations, in both the mass selection and family lines, by producing, where possible, improved lines every year rather than every two years as currently. Performance assessment will continue through to the second year.
2. develop a selection index which uses all information about genetic merit over several commercial traits. This is the sum of the commercial gains an individual can transmit weighted by commercial value.
3. monitor grow-out performance at one year of age and two years of age, to determine if crosses can be made at one year of age rather than two years. This would speed selective improvement. We need to assess whether performance at one year is a good indicator of performance at market size (currently ~2.5 years).

If the Joint Venture company (JVC) proposed to commercialise our work is not established, then we will need to:

4. work with industry to conduct trials of particular lines in both Tasmania and South Australia under full commercial conditions.
5. develop sophisticated long-term breeding plans which yield on-going performance improvements while avoiding the deleterious effects of inbreeding. These plans will be based on analysis of data collected during the project, and require a major commitment from both technical staff and geneticists.
FRDC funding is thus required to complete the development program and, if the JVC is not established, to conduct the commercialisation trials and development of breeding plans. If the JVC is established, then we would provide it with broodstock for the trials but would expect it to develop its own long-term breeding strategy with input from and collaboration with our technical staff and geneticists.

A means of quantifying the optimal stocking density of oysters relative to their food resources (quantity and nutritional quality) is a necessary feature in the sustainable management of the oyster industry at a time of increasing demand both for a greater volume of production and improved production efficiency. This has been recognized by the industry as a major need for there to be further development of production. It is also urgent because of increasing scrutiny and regulation under principles of ecologically sustainable development. Maximal development can only be sustainable if local carrying capacity is well understood.

Of the various ways, in theory, of arriving at quantification of optimal densities, an approach which concentrates upon the oyster and its food, measured initially at the scale of the individual lease, is practical and feasible. Once this relationship is defined, it may then with confidence be extended to a variety of habitat conditions, since it will be based upon the fundamental physiological properties of the species.

This proposal aims to define these relationships via rigorous physiological determinations, coupled with appropriate field studies and modelling. The proposed product will be a tool of value to the oyster farmer and to those concerned with planning and approving the expansion of leases within coastal habitats.

A major problem facing Pacific oyster growers throughout southern Australia is maintaining consistent product quality. High levels of genetic variability in oysters cause considerable variation in several economically important traits such as growth rate and condition. Variation in growth rate causes extra work because of the need for frequent grading, while variation in condition within a batch may prevent growers from obtaining a market for their oysters. Even for those oysters which are of sufficient quality to reach the market, supplying oysters that vary in condition, or colour for example, creates a perception of poor quality control and undermines market confidence in the suppliers (and hence in the growers). This variability in product quality is currently unavoidable simply because of the intrinsic genetic variation in oyster stocks.

If genetically uniform oysters could be produced, then a major source of variation in product quality would have been removed from the oyster industry. All oysters grown from a batch of genetically identical spat should respond similarly in any given environment. Consequently, considerable improvements in consistency of product quality and appearance could be achieved. These genetically uniform oysters would still show some variation in (e.g.) growth rate and degree of condition due to differences in the environments they experience — for example, oysters which had been growing at the centre of a basket or lease may gain condition more slowly than those at the edge — however, because this variation would now be solely due to environmental factors, growers would be able to rapidly identify and control these factors. This would increase consistency of product quality still further.

A second major limitation to the oyster industry at present is a lack of stock which have been genetically selected to produce commercially desirable characteristics. Given the wide variation in environmental conditions under which Pacific oysters are grown in Australia (from cold, low-salinity waters off Tasmania, to warm, high salinity waters in S.Australia) considerable opportunity exists to breed oysters which have been genetically selected to perform well in a given environment. The Pacific oyster industry has recently engaged in a research programme which aims to selectively breed oysters that match grower and market demands more closely than present stocks. However, this programme uses conventional breeding techniques, and (commercial) benefits to growers cannot be expected for some considerable time.