The Growth, Abundance and Diet of O-Group Sea Bass,Dicentrarchus Labrax, From the Severn Estuary

Abstract

Eggs of Dicentrarchus labrax (L.) have been collected from the mouth of rivers or inshore waters of salinity greater than 30 p.p.t. (Barnabé, 1978; Kennedy & Fitzmaurice, 1972). The main spawning period is between April and June (Kelley, 1979; Kennedy & Fitzmaurice, 1968), though ripe males have been reported as early as February and as late as mid-July (Kennedy & Fitzmaurice, 1972). The fertilised eggs 1·15—1·51 mm in diameter, are pelagic, take between two and five days to hatch and the prolarvae are 3·25—4·05 mm in length when they emerge (Barnabé, 1976; Bertolini, 1933, pp. 310–331; Lumare & Villani, 1973; Jackman, 1954). Postlarval stages have been recorded from the Bristol Channel in mid-June and mid-July (Russell, 1980) as well as off Plymouth between mid-March and mid-July (Russell, 1935, 1976; Russell & Demir, 1971). Although a few juveniles have been encountered, from the middle and lower reaches of estuaries, during their first summer (Kennedy & Fitzmaurice, 1972), it is not until the autumn/winter that relatively large numbers of o + bass have been reported from British estuaries (Claridge & Potter, 1983; Hardisty & Huggins, 1975; Hartley, 1940; Murie, 1903; Van den Broek, 1977; Wheeler, 1979). Juvenile bass have also been recorded from lagoons and coastal waters, during their first summer, indicating that these are important nursery areas (Arias, 1980; Barnabé, 1978; Chervinski & Lourie, 1972; Ferrari & Chieregato, 1981; Gandolfi, Rossi & Tongiorgi, 1981).