SPATIAL AND TEMPORAL ORGANIZATION OF LAGO ON FISH COMMUNITIES (RIA-FORMOSA IN PORTUGAL AND GRAND-CUL-DE-SAC-MARIN IN GUADELOUPE)

Fish communities from two lagoon ecosystems, Ria Formosa (Portugal) an d Grand Cul-de-Sac Marin (Guadeloupe), show interesting similarities o f spatial and temporal organization. On the temporal scale, three comm unity changes are observed in both systems, corresponding to massive a rrivals and/or departures of migratory species. However, these migrati ons are more conspicuous in the Ria Formosa than in the Grand Cul-de-S ac Marin. On a spatial scale, the community structure is also largely determined by migratory species, whose abundance is a factor of homoge nization. This is clearly observed in Ria Formosa, where the lagoon se lection applies on a regional scale. Conversely, the community of sede ntary fish identifies remarkable stations affected by chronic aggressi ons such as tourism or pollution. An explicative analysis, comprising a discriminant analysis and multiple regressions was realized on the d ata collected in the Grand Cul-de-Sac Marin. This analysis made it pos sible to determine the important environmental descriptors in the two complementary processes involved in recruitment: migrant availability, which determines the temporal organization of the fish assemblage. Th ese migrations are explained by water temperature and salinity, two de scriptors controlled by climatic conditions; the settlement process, w hich determines the spatial organization of the fish assemblage. This is explained by habitat descriptors such as visibility and turtlegrass blade length, or trophic descriptors, such as primary production, zoo plankton density or nitrate concentration.