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

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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 coefficient 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.

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