METAMORPHOSIS AND CHANGES IN LIFE PATTERN S IN SOLE POPULATIONS - A REVIEW OF DATA COLLECTED DURING A 5-YEAR SURVEY (1986-1990) IN THE VILAINE ESTUARY (FRANCE) AND PROSPECTS FOR RESEARCH

Interannual comparisons of settlement processes of young sole on a nur sery area show that the first cohorts to arrive are mainly composed of metamorphosing soles whose inshore migration is controlled by the the rmohaline conditions of the estuary. Their spatio-temporal distributio n patterns are similar whatever the survey year. Most of the metamorph osing soles exhibit a vertical migratory behaviour, accumulating on th e bottom during the day, and dispersing throughout the water column at night. Soles which do not act in this way, have a feeding rhythm weak ly linked to the tidal cycle. Owing to the time and spatial discrepanc ies between the distribution of sole and of the gelatinous predators i n the estuary, the mortality rate in sole due to predation is slight. Finally, a conceptual model on relationships between the physiological processes occurring during metamorphosis and the environmental parame ters of the estuarine areas is proposed.