The role of coastal areas in the life history of sole (Solea solea, L.) in the Bay of Biscay

Abstract

The importance of shallow-water and the estuarine environment for the sole (Solea solea L.) of the Bay of Biscay is evaluated. Like many estuarine-dependent species, the Bay of Biscay sole is an offshore spawning population. Spawning takes place at depths varying between 50 and 100 m in early spring. Post-larval stages and early juveniles arrive in the inshore shallow areas where they continue their growth for about two years. Mature fish emigrate offshore during winter to participate in the reproduction process. The shallow areas and the estuaries are an essential habitat for the juveniles of this species since no 0 or I-group juveniles have been observed in deep waters. The survey of sole juveniles in the bay of Vilaine (Northern part of the Bay of Biscay) reveals an ontogenic offshore migration characterized by seasonal changes. Juveniles as they grow move to deeper waters but in summer the individuals are in shallower areas than during winter. The ability of the individuals to react against environmental conditions increases with age. Stressful conditions affect the young individuals shortly after settlement. The I-group juveniles are able to detect even short term environmental fluctuations. They respond frequently by an offshore migration in order to reach deeper more stable waters. Tagging experiments show that the juveniles of the bay of Vilaine are dispersed all over the Bay of Biscay without any preference during their pre-spawning emigration. No particular linkage between a spawning ground and a nursery area was detected.