The Sydney Rock Oyster breeding program is transitioning from mass selection to a multi trait family breeding program guided by geneticists at CSIRO. What does this mean?
Mass selection is a process whereby a population of oysters are selected for one or two traits, for example fast growth and QX disease resistance. Each year, survivors of QX disease, and fast growing animals will be selected from the population and induced to spawn. The progeny form the next mass selected population, and the process repeats whereby survivors and fast growers within the next generation are selected for spawning. This technique has made substantial gains in growth and disease resistance over the past 20 years (see Science and Extension). However, there is little control over which male fertilises which female, and therefore after several generations the risk of inbreeding increases.
By contrast, family breeding is a multi trait, full sibling model. Oysters are managed in their separate families, and controlled fertilisations allow us to know which family is used to select a male and a female to cross. This model allows us to capture pedigree information of each family, and therefore control inbreeding. It also allows us to incorporate multiple traits, and quantify the heritability of each trait through time using quantitative genetic tools. This allows for significantly faster gains in selected traits at each generation.
We are selecting Sydney Rock Oysters for weight, QX disease resistance, WM resistance, condition, and shell shape. The relative gain in each trait at each generation is quantified using an Estimated Breeding Value (EBV) and therefore we can accelerate gains by selecting families with the highest EBVs for traits of interest. Family breeding is used in salmon, cattle, wheat, merino sheep, and the poultry industries to name a few.
Working in partnership with NSW DPI Fisheries, SOCo owns and manages the data which is housed and analysed on a CSIRO database and server, and manages the agreement with CSIRO through funding provided by the FRDC and Oysters Australia IPA.
NSW DPI Fisheries is the operational breeder, who undertake the family production runs each Oct/Nov at Port Stephens Fisheries Institute. The DPI also runs the performance trials of each of the families in several estuaries to test for disease resistance, growth and condition. Each November the expectation is that 40 + families will be created, i.e. one Year Class. Every family is performance tested, added to the pedigree database and added to the founder population, incorporating genetic information from several year classes and several origins (going back to 2006).
Traits which we chose to keep and improve in the gene pool for the long term breeding plan are disease resistance, growth, and condition index. These traits have been targeted by SOCo based on industry priorities and what is genetically possible. Heritability of gains of each trait are assessed using performance trials managed by NSW DPI Fisheries in several estuaries. For instance oysters from each family are deployed in the Georges River and the Clarence River to quantify survival during QX disease. Survival data determines the strength of each family, i.e. level of QX resistance. For condition, trials are done in Wallis Lake and Port Stephens, measuring shape, meat and whole weight.
Selection of broodstock that has gone into the breeding program over the past 10 years has incorporated wild lines from twelve estuaries including Clarence River (for a new QX mass selected line), Nambucca, Camden Haven, Hastings, Port Stephens, Wallis Lake, Hunter, Hawkesbury & Georges River (for the original and a new QX line), Shoalhaven, Turros and Merimbula. Incorporating wild stock from a diversity of estuaries is an important factor in assuring genetic diversity while capturing key commercial traits.
There is limited performance data for Winter Mortality disease resistance. Performance trials for WM disease resistance among families will begin in 2017 and provide better knowledge of selecting for resistance to this disease.
As is the nature of any breeding program, making gains in one trait can cause reductions in another; there are trade-offs. SOCo makes selection decisions to maintain as good a balance as possible to achieve steady gains each year, based on what is genetically achievable and sustainable.
SOCo manages the commercial lines of broodstock in seven NSW estuaries: Camden Haven, Manning, Wallis, Karuah, Shoalhaven, Clyde and Wagonga. Currently there is one mass selected line still used commercially due to industry feedback on the quality and demand: a WMR line. This line was originally selected for fast growth and resistance to Winter Mortality disease. However, due to OsHv-1 virus in the Georges River, which enforced biosecurity closures on broodstock held in the Georges River for selection of this trait, the new generation of stock has not been bred from survivors which may impact its performance in a Winter Mortality event. Therefore SOCo, with help from the NSW DPI will undergo performance trials in 2017 using a cohort of this stock to investigate its level of resistance.
Family lines are now commercially available. Genetic integrity is of utmost importance. SOCo conducts regular inspections, manages broodstock whereabouts, and hatchery broosdtock supply. SOCo will communicate with hatcheries and the industry on the predicted gains, and selection objectives for every commercial family cross. See our 'Broodstock and Family Lines' page for up to date information on currently available lines, and 'Hatcheries and Nurseries' page for hatchery information.
SOCo channels its resources into increasing hatchery production, broodstock care and conditioning, and breeding decisions that reflect industry priorities and ensure the longevity of the program. We aim to increase hatchery production to at least 30 million spat each year over the next 5 years. SOCo’s long term vision for the future is to make the breeding program commercially viable, sustainable, and industry owned.