REPRODUCTION AND RECRUITMENT OF NUCULOMA-TENUIS (BIVALVIA, NUCULOIDA) FROM LOCH-ETIVE, SCOTLAND

A population of the protobranch bivalve Nuculoma tenuis at a depth of c. 54 m in Loch Etive, West Scotland, was sampled monthly from September 1986 to October 1988. The density of N. tenuis in the samples, and the relative proportions of adults and postlarvae, varied markedly from month to month suggesting patchiness at the scale of the sampling. There was evidence for spatial segregation of adults and postlarvae. A seasonal reproductive cycle occurred, with a synchronised spawnout in winter; the exact timing appearing to vary in successive years by up to 2 months. Despite markedly seasonal spawning, no recruitment peak was evident in shell-length frequencies, and benthic postlarvae were present throughout the year. This corroborates Findings from an earlier laboratory study, suggesting a prolonged phase of meiobenthic development in this species.