The biology of Calocaris macandreae [Crustacea: Thalassinidea]

Abstract

Previous work on the biology and distribution of Calocaris is discussed briefly. The distribution in Northumberland waters is considered in relation to depth and bottom sediment.Quantitative monthly samples show that population numbers remain very stable throughout the year. A well marked egg-laying period occurs in January-February when relatively few eggs (average 38) are attached to the pleopods. Eggs are carried for 8–9 months and hatch in September-October. By a combination of size-frequency distribution and gonad-developmnt classification the age-groups in the population are interpreted. After passing through a phase of testes development and spermatophore formation individuals lay their first batch of eggs at the end of the 5th year. The ovaries regenerate over a 2-year period and a second egg-laying takes place at the end of the 7th year with a possible third at the end of the 9th year. The incidence of soft individuals in the samples together with observed changes in the coverage with epifaunistic growths indicate that after entering the 5th year a single annual moult cycle begins with a slowing down in growth rate.Population numbers, fecundity and larval survival are discussed. Both the survival curve and the apparent lack of serious predation suggest that the population reaches senescence