AGE, GROWTH AND MORTALITY OF DOG SNAPPER LUTJANUS JOCU (BLOCH & SCHNEIDER, 1801) IN THE NORTHEAST COAST OF BRAZIL

Abstract

The age and growth of Lutjanus jocu was assessed through readings of growth marks in sagitta otoliths. From August 1996 to March 2000, fish were sampled (n=3.539) in the northeast portion of the Brazilian Exclusive Economic Zone. Sagitta otoliths were extracted from a sub sample of 216 individuals caught around the oceanic bank Sirius (03°59' s; 35°59' w) and over continental shelf from Ceará (05°03's; 36°02'w) to Bahía States (09°01's; 35°12'w). Opaque bands, presumed to be annual, were observed on whole (n= 210) and sectioned (n= 197) otoliths, showing ages from 0 to 20 and from 0 to 25 years respectively. The von Bertalanffy growth model was fit to length-at-age data resulting in the values of L∞= 77.22 cm, K= 0.110 and t0=-3.73. Incremental widths from the first to twentieth opaque band on sectioned otoliths (n = 39) were used on back calculation of length-at-ages and the estimated values were L∞= 71,20 cm, K= 0.112 e t0=-4.32. Otolith reading from sections is a reliable technique for aging L. jocu, which presented medium to high longevity and slow growth. Total mortality (Z) estimated by the catch curve was 0.134 corresponding to an annual survival rate of 87.5%. The natural mortality (M) estimated by the Ault et al. (1998) methodology was 0.12 for 25 years of longevity.