AGE STRUCTURE OF FEMALE GIANT TIGER PRAWNS PENAEUS-MONODON AS INDICATED BY NEURONAL LIPOFUSCIN CONCENTRATION

Fluorescent lipofuscin granules were found in the brains of both wild and pond-reared, mature, female giant tiger prawns Penaeus monodon. Li pofuscin concentrations, measured via image analysis of fluorescence m icrographs, were significantly higher in the brains of 15.3 mo old pon dreared prawns than in those 8.0 mo old. Cluster analysis of lipofusci n concentrations and morphometric data, when calibrated using the know n-age pond-reared prawns, suggested that individuals from a wide range of ages, corresponding to 3 semi-annual cohorts at roughly 12, 18 and 24 mo of age, were present in the sample of mature wild females from the Cairns region of northern Queensland, Australia, in September 1993 . As expected from earlier studies and as indicated here by discrimina nt function analyses, these apparent cohorts were more readily differe ntiated using lipofuscin concentration than either carapace length or weight. Use of lipofuscin concentration as a proxy measure of age sugg ested that growth of sampled prawns was similar to that previously rep orted for the species obtained using conventional methods. Lipofuscin concentrations were generally low and individual variation relatively high in this species, as is apparently the case for other prawns. Howe ver, this study suggests that age pigment can be useful for population age structure assessment in penaeids. The mixture of ages present in the wild female P. monodon population may indicate a potential source of variation in broodstock quality for future investigation.