IMPROVING INDUCED SPAWNING OF SNOUT OTTER CLAM (Lutraria rhynchaena JONAS 1844)

Snout otter clam Lutraria rhynchaena, a bivalve species, is a delicious seafood and commercially maricultural species in the northern and the central provinces of Viet Nam. However, this species cannot be developed and expanded to meet the market demand due to insufficient seed supply. Normally, in the protocol of seed artificial reproduction for bivalve, the broodstocks are stimulated to release eggs and sperm. In the case of Snout otter clam, the induced spawning is often used high thermal shock by weak sunlight exposure, but its results are inefficient. Therefore, this paper aims to improve the induced spawning for seed artificial reproduction of Snout otter clam. Based on the ratio of fully developed veliger larvae stage of Snout otter clam in different induced spawning methods, high thermal shock by weak sunlight exposure (for control), low thermal shock by ice packs, and high pH shock by chemicals in filtered natural seawater. The methods of pH shock at 9.5 for 20 minutes and the low thermal shock at 15oC for 20 minutes were able to select for improvement of induced spawning of Snout otter clam due to the broodstock recovery ability, high ratio of the broodstocks to reproduce, high ratio of fully developed veliger larvae stage. Thus, these two methods of stimulation could be applied of the artificial reproduction of snout otter clam for commercial scale.