Dynamics of reproduction in a captive shrimp broodstock: unequal contribution of the female shrimp and a hidden shortage in competent males

摘要

The major bottleneck in the breeding hi captivity of penaeid shrimp is the fact that females do notspontaneously undergo vitellogenesis, which thus has to be induced endocrinologically by eye-stalk ablatioa Partial compensation for the low responsiveness of the females to this treatment isobtained by the use of very large broodstock populations. This old problem was newly approachedin the current study by monitoring individual female life-spans and vitellogenic cycles in a smallpopulation of the Pacific white shrimp, Litopenaeus vannamei. Vitellogenic activity and spawningpeaked during the second month of the four-month trial and decreased thereafter due to the sharpfall hi the number of reproductively active females. Only about 75% of all the females in thebroodstock were reproductively active, and most of them spawned for the first time, or exhibitedfully vitellogenic ovaries, during the first two weeks post-ablation. Nevertheless, the bestperforming females, which comprised less than 20% of the female broodstock, matured morerapidly, exhibiting fully vitellogenic ovaries 4.1 +- 3.4 days after eye-stalk ablatioa These animalscontributed more than 50% of the total eggs and nauplii produced. The total number of vitellogeniccycles recorded from all reproductively active females was 305, but in less than a third of thesecycles were the females observed to be carrying spermatophores or sperm masses. Sincefemales--but not males--in captivity undergo accelerated reproductive cycles due to the endocrineinduction, it is suggested that the lack of mating consistently reported from maturation systems maybe due to the lack of sufficient ready-to-mate males.