The annual pattern of condition and maturity in bass, Dicentrarchus labrax, in waters around England and Wales

Morphometric data on bass, Dicentrarchus labrax L. (Pisces: Percoidei), sampled around the coasts of England and Wales between 1982 and 1990, have been analysed to elucidate seasonal patterns of feeding, body condition and gonad maturity. The somatic condition and fat reserves of bass in the Irish Sea and southern North Sea improved more rapidly during the spring and summer than in bass further to the south. In winter, however, fat reserves were higher and there was more food in the stomachs of bass caught in the western English Channel. The onset of maturity was related to fish length. Male bass became mature for the first time at 32-36 cm total length, but though many females showed signs of gonad growth at this size, no female <42 cm was found with mature (ripe or spent) gonads. Gonad development in adult bass of both sexes began in October and, from January until June, most males >36 cm had ripe testes. The period during which ripe eggs could be expressed from the ovaries of female bass was briefer, with spawning apparently peaking in April. It is concluded that the migration of adult bass to the north in spring and southwards and westwards in autumn has both growth and reproductive benefits related to sea temperature, and that the more limited movements of bass <42 cm, which remain in relatively cold, inshore waters in winter, results in an inhibition of gonad maturity in females.