Age estimation, growth, maturity, and distribution of the bluemouth rockfishHelicolenus d. dactylopterus(Delaroche 1809) from the Rockall Trough

Abstract

This paper presents data on the age, growth, maturity, and distribution of Helicolenus d. dactylopterus (Delaroche 1809) from the Rockall Trough area. The results are based on a series of deep-water trawl surveys carried out on the continental slope west of Ireland and Scotland between 1992 and 1993. Ages ranged from 1 to 43 years for males and 1 to 37 years for females with most fish aged between 3‐14 years. The species was found to be sexually dimorphic with males attaining a greater length and weight (L£=37.2 cm; W£=747 g) than females (L£=31.0 cm; W£=700 g). Age and growth estimates were determined for both sexes and the Brody growth coeYcient for both sexes indicate that this species is relatively slow growing (male K=0.06; female K=0.09). Ripe female fish were only found in April and May in a specific area. Using total lengths 50% of male fish were mature at 26 cm (ages 15‐16) while 50% of female fish were mature at 23 cm (age 13). Catch data were sporadic but the largest catches were obtained on the southern slope of the Rockall Trough in April at a depth of 650‐950 m. The fish from this area had a much greater range of sizes than fish from the eastern slopes of the Rockall Trough. ? 1999 International Council for the Exploration of the Sea