Observations on the breeding and growth of the giant freshwater prawn Macrobrachium rosenbergii (de Man) in the laboratory

Abstract

Three male and 20 female prawns, Macrobrachium rosenbergii (de Man), were observed for 390 days. They were maintained in brackish water (5%. salinity) at 28°C which was recycled continuously through a percolating biological filter. Illumination was artificial and did not exceed 10 lm/ft 2 (approx. 0.1 m 2) at the water surface. Mating readily occurred in the experimental tanks (48 × 28 × 25 cm deep). Eggs were incubated for 20 days; the mean number of larvae per brood was 24 000 (range 50–98 100). Over 750 000 larvae were hatched during the experiment. Larger females had proportionately larger broods and larvae from seven broods were cultured to the post-larval stage at intervals throughout the experimental period, which demonstrated their viability. The increase in length of the adults at each moult was constant (arithmetic growth) and did not alter when ova were maturing in the ovary. Prawns achieved larger mean length increments after the environmental conditions were improved. The moulting frequency was very variable and, with one exception, did not change proportionately with length or age of the prawns. Females grew from 115 to 205 mm and males from 145 to 230 mm total length. Three females spawned more than four times in successive intermoult periods, and one produced viable larvae five times in succession. Two of the males sired viable larvae four and seven times respectively during one intermoult period.