Spawning induction of three tropical sea cucumbers, Holothuria scabra, H. fuscogilva and Actinopyga mauritiana

Abstract

Tropical sea cucumbers, Holothuria scabra, H. fuscogilva and Actinopyga mauritiana were collected from the wild, held in insulated containers and transported by a combination of sea, air and road transport for up to 12 h. Methods for obtaining reliable supplies of fertilised eggs from wild-caught broodstock were investigated. Of the 779 H. scabra collected, 4.5% eviscerated during transport, compared with 11.0% of the 181 H. fuscogilva and none of the 52 A. mauritiana. Experiments conducted in 20-l containers, with and without sea water and temperature control, determined that H. scabra survived for over 80 h, H. fuscogilva for 8 h and A. mauritiana for 20 h, in static seawater at 29 °C. Spawning of H. scabra in Solomon Islands can be induced throughout the year, but only in 3 months for H. fuscogilva (from August to October), and 2 months for A. mauritiana (from October to November). The peak spawning period for all three species was during the dry season: August–November. Collection, transport and thermal stress was an effective spawning induction method for H. scabra and A. mauritiana. Induced egg production in H. scabra was greatest in September, when 35% of broodstock spawned. Spawning appeared to be entrained to a lunar cycle in H. scabra, and occurred more readily during the afternoon and early evening. Addition of dried Schizochytrium sp. induced spawning in H. fuscogilva and was far more effective than thermal induction. Females of all three species were highly fecund and capable of multiple spawning. The mean number of fertilised eggs was: 1.9 million (±0.6 S.E., n=17) for H. scabra; 2.6 million (±0.2 S.E., n= 5) for H. fuscogilva and 2.6 million (±0.1 S.E., n=6) for A. mauritiana. The techniques for inducing spawning identified in this study allowed the collection of fertilised eggs for experimental and pilot-scale mass production of juvenile sea cucumbers. Further research should target improved spawning induction through the conditioning and holding of captive broodstock.