Age, growth and mortality of dog snapper Lutjanus jocu (Bloch & Schneider, 1801) in the northeast coast of Brazil

Abstract

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 t 0 = -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 t 0 = -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. R E S U M OIdade e crescimento do Lutjanus jocu foi determinada através da leitura de marcas de aposição em otólitos sagittae. 216 indivíduos, capturados no entorno da montanha oceânica Sirius e na plataforma continental do Ceará (05°03's; 36°02'w) até a Bahia (09°01's; 35°12'w) tiveram seus otólitos extraídos. Marcas opacas que provavelmente formam-se anualmente foram observadas em otólitos inteiros (n=210) e em otólitos seccionados (n=197) apresentando peixes com idades entre 0 a 20 e 25 anos respectivamente. O modelo de crescimento de Bertalanffy ajustado por métodos não lineares dos mínimos quadrados aos dados de idade e comprimento resultou em valores de L∞= 77,22 cm, K= 0,110 and t 0 = -3,73. Medidas incrementais da 1ª a 20ª marca opaca em otólitos seccionados (n=39) foram usadas para retrocalcular os comprimentos e as respectivas idades resultando em valores de L∞= 71,20 cm, K= 0,112 e t 0 = -4,32. Leitura de otólitos seccionados de L. jocu é uma técnica confiável para a determinação da idade e crescimento desta espécie, que apresentou longevidade de média a alta com crescimento lento. A taxa de mortalidade total (Z) estimada através da curva de captura foi 0,134 correspondendo a 87,5% de sobrevivência anual. A mortalidade natural (M) calculada pelo método de Ault et al. (1998) foi 0,12 para uma longevidade de 25 anos.

Age and growth of the dog snapper Lutjanus jocu (Bloch & Schneider, 1801) in Abrolhos Bank, Northeastern Brazil

“…For instance, our readings of whole otoliths for fish between 0 and 6 years tended to overestimate age estimates when compared to those of sectioned otoliths. We were unable to distinguish growth rings for fish older than 6 years when reading whole otoliths, and this fact was also reported by (Rezende & Ferreira, 2004). Therefore, readings of whole otoliths were further dismissed, and we only present age estimates based on sectioned otoliths.…”

“…6). However, based on other studies from this species (Claro et al, 1999;Rezende & Ferreira, 2004), we assumed that age rings are annual.…”

“…Otoliths of younger fish grow primarily in length, but from 8 years on there is a noticeable increase in thickness (Rezende & Ferreira, 2004), compromising the count of rings without sectioning. For instance, our readings of whole otoliths for fish between 0 and 6 years tended to overestimate age estimates when compared to those of sectioned otoliths.…”

“…The spawning season of L. jocu is winter to spring; maturity is reached from 30.5 cm in females and 26.6 cm in males (Freitas et al, 2011). Other biological aspects of the species have been studied in Brazil, such as age and growth by Rezende & Ferreira (2004) and diet by Monteiro et al, (2009). According to the latter authors, L. jocu feeds on many families of crustaceans, mollusks, and teleosts.…”

Baía de todos os santos: aspectos oceanográficos

“…Em relação ao vermelho, os parâmetros foram L∞=31,2 cm e k=0,17, e o tamanho máximo observado foi de 42 cm e a idade de 17 anos (Leite Jr. et al, 2005). O dentão também é uma espécie de crescimento lento e de vida longa (L∞=77,22 cm, k=0,11) (Rezende e Ferreira, 2004). …”