Nutrition is among one of the major aspects, which can be at the origin of reproduction difficulties in oyster hatcheries. In commercial hatcheries, broodstock conditioning requires large quantities of phytoplankton and the choice of the algal species is generally dictated by its suitability for mass-production at a low cost under the environmental conditions of the hatchery rather than by its optimal nutritional value for the oyster. This empirical approach is at the origin of deficiencies in the algal diet for the broodstock, which may affect various aspects of reproduction, including spawning success, egg quality, and the growth rate, sensitivity to stress and pathogens of the larvae. This project aims at the improvement of broodstock management in oyster hatcheries through a better understanding of the relation between broodstock nutrition and quality of early life stages, with the following specific objectives:
1. Document problems in current hatchery practice by comparison of nutritional aspects of reproduction under natural and artificial conditioning
2. Identify critical nutrients for broodstock nutrition
3. Define artificial diets to supplement these nutrients to live algae, taking into account the initial nutrient storage of broodstock
4. Improve cost-efficiency of broodstock conditioning
The first year activities, being the sampling campaign in nature and two broodstock conditionings have been done. The histological and histochemical observations, biochemical analysis and the glycogen metabolism were evaluated and a comparison between the artificial broodstock conditioning and the natural conditioning were made. The effects of both conditions on the production parameters and on biochemical composition of the eggs and D-larvae were also evaluated. Formulation of diets, verification of ingestion and assimilation were done and a supplementation feeding strategy for the next broodstock conditioning is proposed. The development of standardised stress and challenge tests are still in progress and will be tested on the output of the next spring broodstock experiment.
Nutritional deficiencies in algal diets, importance of nutrient storage and oyster requirements will be assessed through the characterisation of histological, histochemical and biochemical events during the reproductive cycle under natural and hatchery conditions. Four research groups with complementary experience in artificial diets, bivalve nutrition and broodstock conditioning, and bivalve reproduction will work on the problem of oyster nutrition in collaboration with three European hatcheries and one company specialised in larviculture diets. The hatcheries will contribute to validate the experimental results under their specific culture conditions.
Funding SchemeCSC - Cost-sharing contracts
15706 Santiago De Compostela