Composition of fish communities in a European macrotidal salt marsh (the Mont Saint-Michel Bay, France)

At least 100 fish species are known to be present in the intertidal areas ( estuaries, mudflats and salt marshes) of Mont Saint-Michel Bay. These and o ther comparable shallow marine coastal waters, such as estuaries and lagoon s, play a nursery role for many fish species. However, in Europe little att ention has been paid to the Value of tidal salt marshes for fishes. Between March 1996 and April 1999, 120 tides were sampled in a tidal creek. A tota l of 31 species were caught. This community was largely dominated by mullet s (Liza ramada represent 87% of the total biomass) and sand gobies (Pomatos chistus minutus and P. lozanoi represent 82% of the total numbers). These s pecies and also Gasterosteus aculeatus, Syngnathus rostellatus, Dicentrarch us labrax, Mugil spp., Liza aurata and Sprattus sprattus were the most freq uent species (>50% of monthly frequency of occurrence). In Europe, salt mar shes and their creeks are flooded only during high spring tides. So, fishes only invade this environment during short immersion periods, and no specie s can be considered as marsh resident. But, the salt marsh was colonized by fish every time the tide reached the creek, and during the short time of f lood, dominant fishes fed actively and exploited the high productivity. Nev ertheless, this study shows that there is little interannual variation in t he fish community and there are three 'seasons' in the fish fauna of the ma rsh. Marine straggler and marine estuarine dependent species colonize marsh es between spring (recruitment period in the bay) and autumn before returni ng into deeper adjacent waters. Estuarine fishes are present all year round with maximum abundances in the end of summer. The presence of fishes confi rms that this kind of wetland plays an important trophic and nursery role f or these species. Differences in densities and stages distribution of these species into Mont Saint-Michel systems (tidal mudflats, estuaries and tida l salt marshes) can reduce the trophic competition. (C) 2000 Academic Press .