Growth and motality parameters of the snowy grouper, Epinephelus niveatus (Valenciennes) (Osteichthyes: Serranidae), off southeastern Brazil

Abstract

The snowy grouper, Epinephelus niveatus (Valenciennes) is a commercially important demersal fish from southeastern Brazil, inhabiting coraline and rocky substrates of the outer shelf and upper continental slope. Age, growth and natural mortality of this species were studied through catch sampling from August 1996 to August 1997. The data analysis was based on readings of the scale's age rings of 229 specimens in the size range of 33.0 — 93.4 cm TL. Scales were found to grow on an isometric proportion with fish length and there is an annual periodicity in age ring formation, which takes place on November-December. Back-calculated mean total lengths ranged from 27.5 cm at the end of age group I and 92.4 cm at the end of age group XII. The growth equation in total length (cm) is Lt = 148.4 [1 - e ^{-0.069 0 + 2.97}).1, with the corresponding one in weight (kg) being W_t = 45. 7 [1 - e ^{- 0.069 (1+ 2.97)}] ^2.904 obtained from the weight/length regression equation: in W = - 10.698 + 2.904 ln L. The annual natural mortality coefficient was M = 0.170. The snowy grouper has low growth coefficient (K = 0.069), high ratio K/M = 2.5, and great longevity (t_max = 46.4 years) characteristics typical of carnivorous species of the fifth trophic level. There was found to be a similarity in the growth parameters between the southern Brazil and southern Florida (USA) snowy grouper populations.