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.Lipofuscin concentrations, measured via image analysis of fluorescence micrographs, were significantly higher in the brains of 15.3 mo old pondreared prawns than in those 8.0 mo old.Cluster analysis of lipofuscm concentrations and morphometric data, when calibrated using the known-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, Austraha, in September 1993.As expected from earlier studies and as indicated here by discriminant function analyses, these apparent cohorts were more readily differentiated using hpofuscin concentration than either carapace length or weight.Use of lipofuscin concentration as a proxy measure of age suggested that growth of sampled prawns was similar to that previously reported 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.However, this study suggests that age pigment can be useful for population age structure assessment m 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.