The suitable dietary levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were determined for larval mud crab during the Artemia feeding period. Two feeding experiments were carried out in one liter plastic beakers, each containing 30 larvae (first stage zoea) and later fed Artemia enriched with different levels of DHA (0-2.9%) and/or 1.2-2.2% of EPA on a dry basis were used from the zoea 3 stage. The survival rate, carapace width of the first crab and total days to reach each stage of larval development were measured.
The crab fed unenriched Artemia containing 1.3% EPA alone showed the best survival rate and highest molting rate. A high survival rate and large carapace width of the first crab were also observed in the crab fed DHA-enriched Artemia containing traces to 0.46% DHA (plus 1.3-1.7% EPA). However, DHA levels in Artemia of more than 0.46% (plus 1.7% EPA) resulted in low survival rate, especially when the Artemia contained 2.9% DHA, due to mortality linked to molting failure prior to the megalopa stage.
These results suggest that the larval mud crab definitely needs EPA for survival, while DHA was required for the growth of the carapace and the suitable levels of EPA and DHA in Artemia were about 1.3-2.5% and 0.46%, respectively.