SEASONAL AND AGE VARIABILITY IN THE REPRODUCTIVE-PERFORMANCE OF PENAEUS-SEMISULCATUS BROODSTOCK - OPTIMIZING BROODSTOCK SELECTION

The knowledge of the inherent reproductive patterns of wild prawn (shr imp) populations is essential in predicting the expected performance o f hatchery broodstock. In response to problems of variable hatchery pe rformance of penaeid broodstock at some times of the year, the inheren t seasonal variability and the effects of broodstock age on reproducti ve performance of Penaeus semisulcatus were examined. The investigatio n of these effects, using a penaeid for which the detailed reproductiv e ecology was well known, provided a proxy from which to describe the general case likely applicable to other farmed species. During the thr ee-year study, assessments were made for broodstock of known but incre asing age collected from the wild overall seasons (at 2-monthly interv als), and from the two distinct age-cohorts present in the same season . The reproductive performance of the broodstock was assessed at each stage of the maturation and spawning process, Measures of maturation r ate, spawning rate, fecundity, hatch rate, larval survival rate, and l arval production rate were obtained. Inherent temporal patterns in the measures of reproductive performance were found for the main annual c ohort of the wild stock, The rates of spawning, egg production, naupli i production and protozoeae production were lowest in autumn when fema les were 6 months old, increased through to a spring peak (at 12 month s old), and then declined by early summer by which time females were 1 4 months old. Broodstock survival, egg hatching and metamorphosis of n auplii to protozoeae were unaffected by time of year. Trials with two age-cohorts present in the same season enabled us to separate the effe cts of age and season. Twelve-month-old broodstock outperformed B-mont h-old broodstock, regardless of season. Age was the best predictor of reproductive performance. An optimal age of 12 months for best reprodu ctive performance was identified. This information can be used to sele ct broodstock for hatchery production. The findings may be applicable to other species of farmed penaeids. (C) 1997 Elsevier Science B.V.