Movements, abundance, age composition and growth of bass, Dicentrarchus labrax, in the Severn Estuary and inner Bristol Channel

Abstract

The movements, abundance, age composition and growth of bass, Dicentrarchus labrax (L.), in the Severn Estuary and inner Bristol Channel have been described from regular samples offish taken from power-station intake screens between 1972 and 1977. Bass began to move into the estuary during late August or September and reached peak abundance between September and early November. The tendency for fish to move seawards in the late autumn and winter may be related to declining water temperatures in the estuary. Likewise, differences in abundance between years appear to be related to annual differences in temperature. Although the populations were dominated by the 0 + age class, successively decreasing numbers of the next four age classes and occasional 5 + fish were also present. Respective mean standard lengths of bass in the estuary at the end of their first to fifth years of life were approximately 65 mm (≡ 4·5 g), 130 mm (≡ 37·9 g), 190 mm (≡ 121·1 g), 250 mm (≡ 280·4 g) and 290 mm (≡ 441.5 g). Growth occurred predominantly between May and September, with the mean standard length of 1 + fish increasing from approximately 65 mm (≡ 4·5 g) to 130 mm (≡ 37·9 g).