Crescimento e mortalidade de Penaeus subtilis (Decapoda, Penaeidae) na plataforma continental Amazônica

Abstract

The present paper determines the growth parameters and mortality of Penaeus subtilis in the Amazonian continental shelf. Data from biometric samples obtained on board industrial trawlers from 2000 to 2004 were utilized. The growth parameters and natural mortality were estimated using the computer sofware FiSAT II. It has been found that females grow more than males and are always present in greater proportion in catches (61%). Asymptotic lengths were estimated at 231 mm (k = 1,6 year-1) and 205 mm (k = 0,94 year-1) and the values of total mortality were 5,2 year-1 and 5,5 year-1, for females and 1,83 year-1 males respectively. Estimates of natural mortality were: 2,53 year-1 for females e 1,83 year-1 for males. The values of longevity for females (1.88 years) seem reasonable, but for males (3.19 years) they are very high due to the low value of k and the fact that the formula used (3/k) is only an empirical approximation. The estimated values for the growth performance index Ø’ for females (1,54) are compatible with the auximetric grid proposed for peneids, but for males (1,2) they are also very low. For females, the estimated fishing mortality (F) was 2,67 year-1, for a survival rate of 60%, and for males 3,67 year-1, for a survival rate of 40%.