Age and growth of the Atlantic chub mackerel Scomber colias Gmelin, 1789 off Madeira Island

• Autor(a) principal: Vasconcelos, Joana
• Data de Publicação: 2011
• Outros Autores: Dias, Manuel A., Faria, Graça
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.3/1228
• topic: Average Percent Error Index; Length-weight Relationship; Otolith Age Reading; Scomber japonicus; Madeira Island

The Atlantic chub mackerel, Scomber colias Gmelin, 1789, is one of the main fisheries resources of Madeira Island. It is caught by a small and coastal purse-seine fleet that traditionally operates around the island. From January 2002 to December 2003, monthly samples of chub mackerel were collected from landings by this commercial fishing fleet. A total of 2212 sagitta otoliths were extracted for age readings from 1068 males (17.4-41.7 cm total length, TL), 1066 females (18.0-41.2 cm TL) and 78 undetermined (13.0-26.8 cm TL). A single reader aged the fishes using surface-read whole otoliths aiming to build annual age-length keys. Age readings precision and reader consistency were assessed by using the average percentage error index (APE ≤ 1.52). Ages were validated up to 4 years using marginal analyses. Estimated mean lengths at age and length von Bertalanffy growth curve parameters, estimated by non-linear methods, showed no significant differences (p>0.05) between sexes (L∞=50.08 cm TL, k=0.252 yr-1 and t0=-1.339 yr; males and females combined). Length-weight relationships were estimated aiming to convert growth in length to growth in weight. No differences between sexes were found in length-weight parameters (P>0.05). For sexes combined, total weight (TW, g) = 0.00218.LT 3.40 and the estimated asymptotic weight, W∞=1523.7 g.