The effects of diets on reproductive performance of eyestalk ablated and intact mud crab Scylla serrata

Abstract

The reproductive performance of female mud crabs was evaluated as affected by various diets. Dietary treatments were as follows: D₁ — natural diet (mussel meat, squid, trash fish); D₂ — combination of natural and formulated diets; D₃ — formulated diet. Pond-sourced broodstock, with initial body weight of 300–400 g, were tagged in their carapace then stocked in three units of 10 m³ broodstock tanks at eight females per tank. Half of the females were ablated and the other half were intact. Spawnings were monitored and berried females were transferred to individual 500-l tanks for incubation of eggs. Four experimental runs were conducted. Broodstock response in terms of number of spawnings, spawnings with hatching, fecundity, egg fertilization rate, total zoea produced and broodstock survival was enhanced in females fed the mixed diet (D₂) compared to those fed the natural diet (D₁) or the formulated diet (D₃). Larval quality measured as larval stage index followed the same trend. Results further showed that intact females fed diets D₁ and D₂ gave higher numerical values in reproductive performance and zoea growth index than ablated females while ablated females fed diet D₃ performed better than their intact counterparts. This may be attributed to presence of essential nutrients and vitamins A, C, E in the formulated diet. Latent period from gonadal maturation to first spawning was shortened by eyestalk ablation. Use of a combined diet would ensure the production of good quality eggs and large numbers of zoea with the best chance of completing the larval stages and thus, would serve as an appropriate starting point in establishing a viable mud crab aquaculture.