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: log W = -5.3249+3.2107 log L.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.
An investigation was made to compare the reproductive strategies of Crenilabrus melops, Labrus bergylta, Labrus ossifagus, Centrolabrus exoletus and Ctenolabrus rupestris. Fish were collected monthly and measurements were made of length, weight, age and colouration. Histological sections of the gonads were also prepared. Labrus bergylta and L. ossifagus are protogynous, the former monandric and the latter diandric, and a distinct colour change is associated with sex‐inversion in L. ossifagus. The other three species are gonochoristic and only C. melops exhibits sexual dimorphism which involves body colouration and size of the urino‐genital papilla.
All five species undergo normal annual cycles of reproduction which compare with those described for other teleost species, but some differences were noted relating to the different reproductive strategies. L. bergylta females reached sexual maturity at the late age of six to nine years following earlier abortive maturation.
In C. melops two types of male were found: the normal (type 1) males and a minority group (about 20%) termed type 2 males, which have complete female secondary sexual characteristics. Type 2 males also have very large testes and attain sexual maturity two years earlier than type 1 males. Their role in reproduction is unknown.
Sexual inversion in L. bergylta and L. ossifagus occurs by atrophy of the oocytes and the gradual development of spermatogenetic cysts throughout the gonad. Primary and secondary testes can be distinguished histologically and male L. ossifagus with primary testes do not seem to take part in reproduction.
With 4 plates and 3 figures in the text)The burrows of the Red band fish, Cepola rubescens L. are described from casts taken in situ using polyester resin. Observations of behaviour and spatial distribution are presented and the coloration, morphology, age, gonad condition and diet of captured specimens are discussed.
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