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Maturation |
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Although most hatcheries prefer to use gravid females obtained directly from the wild, these females are often in short supply and some operations opt for the alternative of inducing gonad development in captive shrimp. The facility with which broodstock will mature, copulate and spawn in captivity varies greatly between different species. Even in a carefully controlled environment some important species will not mature with regularity, so, in the absence of a proven alternative, the technique of unilateral eyestalk ablation is usually applied. P. indicus and P. japonicus mature, mate and spawn readily in captivity, P. monodon requires environmental and hormonal manipulation (Bray & Lawrence, 1992). In the most simple approach to maturation many hatcheries in south-east Asia obtain wild gravid females (usually P. monodon) and, after the initial spawning, induce four or five additional spawns by eyestalk ablation. Fertilization in such cases relies on sperm retained by the female throughout the inter-moult period. If females develop ripe ovaries but are not impregnated, it is possible to resort to artificial insemination to produce fertilized eggs (Bray & Lawrence, 1992). |
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