Movement of Sole (Solea Solea) in the Bay of Biscay: Coastal Environment and Spawning Migration

Abstract

During the studies on sole recruitment in the Bay of Biscay, transport process attracted considerable attention and led to important research on migration and dispersal. The last step to complete the study of the spatial component of the life cycle of sole in the northern part of the Bay of Biscay is the offshore migration of young adults towards the spawning grounds. the present study deals with this pre-spawning migration. the main question concerns the kind of linkage between nurseries and spawning grounds. The principal results are based on extensive tagging experiments carried out in autumn 1992 in two distinct nursery grounds, Bay of Vilaine and Pertuis (4620 soles of 2-group and older). One year later (January 1994) catches of tagged individuals reached 18.1% and 11.9% of the initial samples, respectively. From September to February a 50-km net displacement of the centre of the population was observed towards the offshore deeper area. A small trend to move onshore appeared in spring. In parallel with these net movements individuals were dispersed around the centre of gravity of the population. This dispersion was higher in a direction parallel to the coast. Individuals from different nurseries were mixed over the same spawning areas of the Bay of Biscay, and some individuals were also captured in and close to the English Channel. Changes in distribution were in phase with environmental changes and some elements concerning topographic preferences also appeared. Some evidence for orientation was observed but random dispersal seemed more important. No particular link between a given nursery and a spawning ground in the vicinity appeared.