Growth, diet and condition of corkwing wrasse and rock cook on the west coast of Scotland

A study of seasonal and sexual variations of growth, diet, somatic condition (K-S) gonadosomatic condition (GSI) and hepatosomatic condition (HSI) of corkwing wrasse Crenilabrus melops (L.), and rock cook Centrolabrus exoletus was made on specimens taken from areas on the west coast of Scotland from May 1992 to February 1994. Capture throughout the year was by baited creel, 3-m beam trawl, fyke net or by anaesthetics applied underwater. Corkwing ranged in size from 31-212 mm and 0 . 3-131 . 2 g for males, and 31-203 mm and 0 . 3-103 . 5 g for females. Maximum corkwing ages were 6+ years for males, 7+ years for females. Male rock cook ranged in size from 43-165 mm, weighed 0 . 7-56 . 5 g, and had a maximum age of 8+ years; females ranged in size from 43-138 mm, weighed 0 . 7-39 . 3 g, and had a maximum age of 4+ years. Male growth rates were faster for both species. Male and female corkwing had low K-S values during the period of high GSI values; the trends for rock cook K-S values were more variable, but levels increased after the reproductive period. Maximum GSI values were 11 . 37 and 18 . 94 for male and female corkwing respectively, 9 . 63 and 16 . 63 for male and female rock cook. There was no seasonal HSI fluctuation for male corkwing, levels were higher during the reproductive period for female corkwing and male rock cook, lower during the same period for female rock cook. The diets of corkwing and rock cook were both dependent on epibenthos. Corkwing diet was dominated by gastropod molluscs. The management of sustainable fisheries for corkwing and rock cook is discussed in relation to the growth rates of the two species. (C) 1996 The Fisheries Society of the British Isles.