Atlantic chub mackerel (Scomber colias) spawning season, size and age at first maturity in Madeira waters

Abstract

The pelagic chub mackerel, Scomber colias Gmelin, 1789 is one of the most important fishery resources in the Madeira Archipelago. S. colias is caught by a small and coastal purse-seine fleet that traditionally operates around the islands. Monthly samples of chub mackerel were taken from commercial landings, between January 2002 and December 2005. Sex and maturity were assigned by visually inspecting the gonads of 1998 males (17.4-46.0 cm total length, TL; 0-5 yr) and 2108 females (18.0-41.2 cm TL; 0-4 yr) using a five-stages macroscopic maturity scale; 99 specimens with undetermined sex (13.0-26.8 cm TL; 0 yr) were also sampled. The analysis of monthly gonadosomatic indices and maturity stages proportions showed that gonad development started slowly in July-August and increased in October-December, for males and females. Spawning took place between January-April peaking in February-March. Maturity ogives were fitted to the observed proportions of mature males and females by using non-linear methods, to estimate size and age at first maturity: 22.12 cm TL at 1.05 yr for males and 21.55 cm TL at 0.82 yr for females