Two experiments involving up to 53 families using this approach were conducted early this year. Moreover, regardless of cohort origin, the pediveligers transferred within the first 24 hours of reaching competency yielded a much higher percentage of settled spat than the pediveligers that were subsequently transferred.īecause up to eight families of larvae are mixed in one tank, the authors now employ DNA pedigreeing to identify the fate of each lineage during the hatchery phase. Surprisingly, the settlement of pediveliger larvae on collectors was much more successful than that of pediveligers in large-volume tanks. For settlement on collectors, the fully competent pediveligers of a cohort were subsequently transferred back to 400-liter tanks. However, on day 2 of larval culture, an equal number of larvae from up to eight families were moved together into a 5-MT tank for larval culture and termed a cohort. In the spawning method that finally proved successful, families were created by mixing gametes from one set of parents only and incubating the embryos in a 400-liter tank. These numbers were of course far too small for a genetics research program, so the system was modified. Only 22 percent of the families metamorphosed into spat, with 142 the highest number of spat recorded in any family. Although typical commercial stocking densities up to 6 larvae per milliliter were used, the volume of sea water proved too small to rear larvae successfully. In an initial round of spawnings in November 2004, the authors produced 41 families and tried to culture them individually in a 400-l tank from incubation to spat stage. In contrast, the genetics research aimed at rearing each family separately during larval culture to simplify the collection of family-specific data. In standard commercial production, the larvae resulting from mass spawnings are cultured in large 5- or 10-metric tons (MT) tanks. Once a broodstock oyster spawned, its gametes were drained and mixed with those of one other broodstock of the opposite sex, thereby resulting in a single family without cross-contamination. Each chamber was supplied with sea water that could not overflow into adjacent chambers. To achieve this, the authors manufactured a spawning table consisting of 10 separate spawning chambers. Therefore, it became necessary to develop a spawning method that allowed the mating of a single female to a single male to reliably produce families. However, since mass spawnings resulted in an unknown number of families with no control over mating pairs, the method was totally unsuitable for genetics research. Due to its simplicity, the procedure was deemed sufficient for the commercial operation. When the spawning started, eggs and sperm from all the broodstock were allowed to mix in an uncontrolled manner. During a typical mass spawning, approximately 30 male and 15 female broodstock were placed on a spawning table. However, the need to modify commercial hatchery techniques to suit the specific requirements of genetics research has already resulted in sometimes unexpected improvements in hatchery management at the Atlas Pacific farms.įor example, the hatcheries traditionally relied on mass-spawning broodstock to produce larvae. The development and implementation of a properly researched selective-breeding program obviously demands patience and a long-term view. maxima, and the consistency and quality of pearl production. If successful, the result will be gains in the growth and survival of P. This will then be followed by the implementation of a selective-breeding program to identify superior breeding strains. maxima, as well as the identification of a suitable founder population.Īt the same time, the molecular tools needed for DNA analysis of the species will be developed. This involves a study on the heritability of growth, survival, and traits relating to pearl quality in P. The initial phase of the estimated four-year project is focused on acquiring fundamental genetic information. and the School of Marine Biology and Aquaculture at James Cook University started a collaborative project aimed at launching a selective-breeding program for P. These pearls, which reach up to 20 mm in size and range in color from silver to yellow and gold, are produced by the biggest of all pearl oyster species, the silver- or gold-lip pearl oyster ( Pinctada maxima). has emerged as one of the major producers of the much desired South Sea pearls. Cendana Indopearls, the Australian-based company Atlas Pacific Ltd. Silver-, gold-lip pearl oysters yield much-desired South Sea pearls Using a new spawning table system with separate chambers, gametes can be collected from individual broodstock.
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