Sea Cucumber Larviculture

Brood stock, collected from the wild, is most commonly induced to spawn through thermal stimulation, by raising the seawater temperature in holding tanks by 3-5 °C for 1 h. S. japonicus broodstock is collected in spring, when mature (Hagen 1996). In general, H. scabra has a bi-annual peak in gonadoso-matic index, indicating two spawning periods a year, but closer to the equator a proportion of the population spawns year-round (Battaglene 1999). Fertilisation occurs spontaneously once the gametes are allowed to mix in seawater; the fertilised eggs are held in suspension by aeration and egg development is rapid. In H. scabra the larval life cycle is around 14 days at 28 °C, including the feeding or auricularia stage, the doliolaria or non-feeding stage and settling pentacula stage (Fig. 4). As with larval sea urchins, holothurian larvae are fed a mixture of microalgal species, with the number of algal cells provided gradually being increased over the larval life. H. scabra larvae grow well on a diet of the red microalgae Rhodomonas salina and the diatom Chaetoceros calci-trans (Battaglene 1999). Further refinement of larval culture techniques is required to improve larval survivorship in this and other species of sea cucumbers.

Fig. 4. The 14-day larval cycle of cultured sandfish (Holothuria scabra) at a water temperature of 28 °C. (Reproduced with permission from Battaglene 1999)
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