Oyster spat field curriculum4/1/2023 A variance component analysis revealed that among the factors studied, 45 percent of the observed variance was due to variation among families. The families were monitored at three sites – Normandy at Baie des Veys, Brittany at Rivière d’Auray, and the Atlantic Coast in the Marennes-Oléron Bay at Ronce – previously known to show different survival rates for juvenile oysters. Due to the resulting variable larval survival and settlement success, heritability estimation of the spat survival in the field was determined using 17 half-sib families, which corresponds to 43 full-sib families. For each set, six males were crossed with four females each following a nested, half-sib design. In 2001, 72 biparental families (G1) were produced in three sets of 24. Within this program, a multisite field experiment was designed to assess the usefulness of selecting for improved survival of oyster spat during its first summer period. Morest, a national multidisciplinary program coordinated by Ifremer, was initiated in France to understand the causes of the summer mortalities in Pacific oysters and propose solutions. A combination of environmental and internal parameters provide a more likely explanation. However, in most cases, the mortality cannot be explained by a single factor. Factors such as temperature, pathogens and physiological imbalances have been suggested to explain the summer mortality phenomena. gigas has been reported for many years and is a major production problem. In France and other countries, summer mortality in C. gigas juveniles, family-based selective breeding has been initiated to improve growth and yield. Recently in the United States, Australia, and New Zealand, where hatcheries are a major source of C. However, the limited extent of hatchery propagation and various technical difficulties and biological characteristics of the species have hampered the development of selective breeding programs. Consequently, significant gains could be obtained by selective breeding of diploid oysters. Several quantitative genetics studies have suggested that significant heritable variation exists for traits of aquaculture interest in oysters, such as disease resistance and growth. Triploid oysters have become increasingly important, as they yield better production performance than their natural diploid counterparts, mainly as a consequence of their high level of infertility. To date, the most significant genetic advance for the production of this species resulted from the development of polyploids. Temperature, pathogens and physiological imbalances linked to summer mortalities Field tests of the Morest Pacific oyster families took place in the Marennes-Oléron Bay and two other sites in France.ĭespite its growing economic importance, aquaculture production of Pacific oysters ( Crassostrea gigas) has not benefited much from genetic improvement.
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