Age, growth and feeding in the ballan wrasse Labrus bergylta Ascanius 1767

A study of the age, growth and feeding of the protogynous wrasse Labrus bergylta (Teleostei: Labridae) was made on 25 male and 316 female specimens taken from the southern coasts of the Isle of Man from October 1972 to October 1974. Age determination and back-calculations for length were made from the opercular bones. The oldest male and female specimens were 29 and 25 years old respectively. The growth curves showed only a slight increase in growth rate after sexual inversion, and a pattern of slow irregular increase, with no pronounced levelling off in old fish. The time of sexual inversion varied widely: intersexual specimens of 5 and 14 years were found. The youngest functional male was 6 years old. The weight/length relationships of males and females were very similar and the following equation, derived from all individuals, was used to calculate weights for age utilizing the back-calculated lengths:
The mouth, pharyngeal teeth and gut length to fish length ratio (0.622) suggested an omnivorous diet. Analysis of gut contents confirmed this, with decapod Crustacea, isopods and molluscs the dominant food items. There were seasonal changes in feeding intensity and composition of the diet, related to temperature changes, onshore-offshore migration patterns, availability of food items, and changes in habitat associated with maturation.