Abstract
Abstract—Seven combinations of aquatic plant extracts were tested to feed juveniles of H. scabra: Thalassia hemprichii, T. hemprichii with 3 % Spirulina, Sargassum latifolium, S. latifolium with 3 % Spirulina, Thalassodendron ciliatum, Syringodium isoetifolium and organic biofilm. A control test consisted in rearing epibenthic juveniles in tank without any food supply. The results showed that extracts of S. latifolium with or without Spirulina gave the best growth and high survival rates: the mean epibenthic volumes were 112 +/- 55 mm³ and 81 +/- 21 mm3 and the survival rates were 60 and 68 % respectively at the end of the experiment (8 weeks). Rearing densities of 150, 300, 450 and 600 individuals m m-2 were tested. The best survival rates (greater than 60 %) were observed in the batches with an initial density of 450 individuals m m-2 or less. The best growth rate was observed with an initial rearing density of 150 individuals m-². The study of biomass showed that the optimum level for the rearing density is 450 +/- 150 juveniles m m-2 . When the parameters of survival, growth rate and biomass (expressed in volume) are all taken into consideration, the optimum rearing density suggested for epibenthic juveniles of H. scabra is between 300 and 450 individuals m-2 . Keywords: Holothuria scabra, epibenthic juveniles, rearing, survival, growth
Highlights
Sea cucumbers, species of the families Holothuridae and Stichopodidae, are overexploited in different regions of the world (Battaglene, 1999b; Conand, 2001, 2004; Conand & Byrne, 1993; ToralGranda, 2006)
The survival rates of epibenthic juveniles fed over the eight week trial period varied from 34 to 66 % (50 individuals per tank at the beginning of the experiment; 17 to 33 individuals per tank towards the end) depending on the food tested while only 7 % of juveniles were alive in the control test (Fig. 1)
The results clearly demonstrate that both food availability and food types affects the survival of epibenthic juveniles of H. scabra (p = 0.0018), no difference was observed between seagrasses and alga (Fig. 1)
Summary
Species of the families Holothuridae and Stichopodidae, are overexploited in different regions of the world (Battaglene, 1999b; Conand, 2001, 2004; Conand & Byrne, 1993; ToralGranda, 2006). Aquaculture is considered as the best solution to decrease fishing pressure and restore natural stocks of sea cucumbers (Conand, 2001; Purcell & Kirby, 2006). Since 1990, several projects have been developed to assess the potential of sea cucumber for small-scaled aquaculture in the Indo-Pacific Ocean where Holothuria scabra Jaeger, 1833 seems the most promising species (Battaglenne, 1999a; James, 2004; Gamboa et al, 2004, Pitt & Duy, 2004). A sea cucumber mariculture project was launched in Toliara (South West of Madagascar) in 1999.
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