A SIMPLE METHOD FOR ESTIMATING GROWTH-PARAMETERS FROM MULTIPLE LENGTH-FREQUENCY DATA IN PRESENCE OF CONTINUOUS RECRUITMENT

The extended recruitment season for short-lived species such as prawns biases the estimation of growth parameters from length-frequency data when conventional methods are used. We propose a simple method for ov ercoming this bias given a time series of length-frequency data. The d ifficulties arising from extended recruitment are eliminated by predic ting the growth of the succeeding samples and the length increments of the recruits in previous samples. This method requires that some maxi mum size at recruitment can be specified. The advantages of this multi ple length-frequency method are: it is simple to use; it requires only three parameters; no specific distributions need to be assumed; and t he actual seasonal recruitment pattern does not have to be specified. We illustrate the new method with length-frequency data on the tiger p rawn Penaeus esculentus from the north-western Gulf of Carpentaria, Au stralia.