Growth of two species of tiger prawn, Penaeus esculentus and P. semisulcatus, in the western Gulf of Carpentaria

Abstract

Growth data were obtained for the two tiger prawn species P. esculentus and P. semisulcatus from a tagging experiment carried out in February 1981 in waters adjacent to Groote Eylandt in the western Gulf of Carpentaria. A von Bertalanffy growth curve was fitted to these data and least squares estimates of the parameters L_∞ and K and joint 95% confidence regions were calculated for males and females of both species. Tests on the residuals from the fitted curve were carried out to check the adequacy of the fit of the von Bertalanffy model, and differences in the parameters L_∞ and K between sexes and species were examined. An alternative von Bertalanffy-type model was used to test the consistency between the estimated L_∞ values and the carapace leilgths of the largest individuals observed in samples from the populations. For males of each species, the fit of the von Bertalanffy model was satisfactory, and the estimates of L_∞ were consistent with the largest observed carapace lengths in catch samples. For females, however, the fit of the von Bertalanffy model was not entirely satisfactory, especially for P. semisulcatus, for which additionally the estimated L_∞ was much higher than the largest carapace length in catch samples. Possible reasons for this lack of fit are discussed. Estimates of L_∞ all differed significantly, with the exception of P. esculentus males and P. semisulcatus males. No significant difference was found in estimates of K for P. esculentus males and females, and only a marginally significant difference in K between P. esculentus males and females and P. semisulcatus males. Presence of a bopyrid parasite in P. semisulcatus did not affect growth.