THE POPULATION-DYNAMICS OF METAPENAEUS-ENSIS (CRUSTACEA, DECAPODA, PENAEIDAE) IN A TRADITIONAL TIDAL SHRIMP POND AT THE MAI-PO MARSHES NATURE-RESERVE, HONG-KONG

The population dynamics of Metapenaeus ensis in a traditional tidal sh rimp pond (locally known as gel wail at the Mai Po Marshes Nature Rese rve, Hong Kong, were studied over a 29-month period. The population of M. ensis was dominated by either one or two age groups throughout the year. Life span was < 16 months. M. ensis is sexually dimorphic in te rms of size, with females growing faster and attaining a larger maximu m size than males. The sex ratio did not differ significantly from 1:1 . The prawns do not mature and reproduce in the gel wai so that the po pulation is sustained by postlarval immigration which begins in June a nd ends in December, with peaks in August and November. The gel wai po pulation of M. ensis is characterized by slower growth, lower maximum attainable size, shorter life span, reproductive sterility and an inco mplete life cycle, as compared with 'natural' populations in the coast al waters of Hong Kong.