Age and growth of the Atlantic chub mackerel

The Atlantic chub mackerel, Scomber colias Gmelin, 1789, is one of the main fisheries re-sources of Madeira Island. It is caught by a small and coastal purse-seine fleet that tradi-tionally operates around the island. From January 2002 to December 2003, monthly sam-ples of chub mackerel were collected from landings by this commercial fishing fleet. A to-tal 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 mar-ginal analyses. Estimated mean lengths at age and length von Bertalanffy growth curve pa-rameters, estimated by non-linear methods, showed no significant differences (p>0.05) be-tween sexes (L∞=50.08 cm TL, k=0.252 yr-1 and t0=-1.339 yr; males and females com-bined). 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 as-ymptotic weight, W∞=1523.7 g