Characterization of Two Substocks of Penaeus kerathurus (Forskål, 1775) Using the Life-History Parameters

Abstract

The growth parameters were determined separately for the two sexes of Penaeus kerathurus, as well as for the two (northeastern and southern) substocks of the species in Tunisia. Seasonal sampling from catches of this species in the coastal and the offshore waters was carried out during the period between 2010 and 2012 for the northeastern substock and between 2010 and 2014 for the southern substock in order to collect length frequency distribution data. The modal decomposition of these distributions by the Bhattacharya’s method and refined by the NORMSEP method made it possible to calculate the mean size of each identified mode, which was attributed an age value by referring to the date of spawning and the date of sampling. Based on these data, the L∞ (cm) and K (yr–1) growth parameters for both sexes of the species were calculated using the Von Bertalanffy model. The results showed that females had a higher L∞ value than males, but the growth coefficient K was higher in males than in females for both stocks. Furthermore, the growth parameters in the northeast and in the south of Tunisia were different. A generalized linear model (GLM) test showed that the growth rate, natural mortality, and performance index of Penaeus kerathurus positively correlated to the sea surface temperature.