The biology and exploitation of John dory, Zeus faber (Linnaeus, 1758) in the waters of England and Wales

Abstract

John dory have become an important by-catch for trawl gears in the western English Channel (ICES division VIIe). English and Welsh LPUE data indicated the John dory stock was centred to the south and west of the British Isles, but extended north into the Irish Sea and east into the southern North Sea during quarters three and four. The growth and exploitation pattern of John dory in the English Channel are described using length samples of commercial landings, discards, and research vessel samples taken between April 1994 and March 1996. In the English Channel the seasonal peak in landings during quarters three and four coincided with the period of recruitment. Recruitment was at a length of approximately 23 cm, most commercial landings were in the length range 23-39 cm, and the maximum observed length was 59 cm. A seasonal growth model fitted to quarterly length data indicted that recruitment took place at age 1+. The mean length of first maturity was estimated at 26 cm in males and 34.5 cm in females, and suggested that the eastern English Channel (ICES Division VIId) was a seasonal nursery ground for John dory. Some options for stock conservation are discussed.