A Study on the Factors Influencing the Growth and Survival of Juvenile Sea Cucumber, Holothuria atra, under Laboratory Conditions

Abstract

In recent years the sea cucumber fishery has emerged as a lucrative business in Mauritius. However, few studies on these marine detritivorous animals have been carried out in the island either in the wild or for aquaculture. The aim of the present study was to investigate the influence environmental factors such as salinity and temperature and biological factors such as stocking density and feed type on the growth and survival of juvenile sea cucumbers Holothuria atra. The study was conducted from mid-October 2006 to end of January 2007 period. For the experiment, 150 juvenile H. atra of similar size and weighing (27-30 g) were collected from Le Morne and Albion Lagoons. The experiments were carried out in round polyether tanks of 2 m³ with an area of 1.5 m² at Albion Fisheries Research Centre. The juveniles H. atra (6 specimens per tank in duplicate) were reared at salinity 25, 30 and 35 ppt; temperature 26, 28 and 32°C; and were given two feed types (crushed algae and a formulated feed (85% crushed algae and 15% fish feed)). For studying stocking density duplicate tanks containing 6, 12 and 18 specimen (per sq m) were used. At one-week intervals, the sea cucumbers were starved for 24h and then weighed. The wet weight was used as an index for its growth performance over the experimental period. The highest specific growth rate (SGR) and survival were obtained at temperature of 28°C (1.43 ± 0.15 g and 100% respectively). At temperature 32°C, the SGR was a lower (0.78 ± 0.12 g) and a survival of 67%. Specific growth rate and survival was lowest in stocking density 18 (0.12 ± 0.23 g & 69% respectively). At salinity of 25 ppt there was decrease in SGR during the experimental period (-4.61 ± 0.29 g). Feeding H. atra with crushed algae produced little increase in growth (0.18 ± 0.16 g) while feeding with formulated feed the specific growth rate was notable (0.97 ± 0.14 g). Under the conditions of the experiments, growth and survival of juvenile H.atra were greatest at 35‰ salinity, temperature 28ºC, and a formulated feed made from algae and dried fish feed and density of 6 specimens per m².

Keywords: Holothuria atra; Salinity; Temperature; Stocking density; Feed type; Specific growth rate (SGR); Survival