Influence de regimes tidaux fortement contrastes sur le recruitement larvaire de la mye commune (Mya arenaria) (French and English text)

Recruitment processes play an important role in the population dynamics of invertebrates in tidal habitats. In contrast to hard-bottom habitats, very few empirical studies evaluate the importance of larval supply in soft-bottom environments. Models developed in hard-bottom habitats may not be used without risk in soft-bottom environments because of fundamental differences between these two habitats.; Hydrodynamic forces influence the distribution patterns of larval and post-larval forms of marine invertebrates. In the intertidal zone, tidal currents represent one of the major hydrodynamic forces that may influence these patterns. The aim of this study was to determine the influence of tidal currents on the larval recruitment of the soft-shell clam (Mya arenaria). The contrasting tidal regimes of the Bay of Fundy (strong tides) and the Northumberland Strait (weak tides) were used to attain our objective.; The intertidal distribution of juvenile and adult soft-shell clams was described using ten stations along the intertidal axis in three sites within each tidal regime during the summer of 2002. The dominant tidal regime did not influence the distribution of soft-shell clams in our sites. The distribution of individuals varied between sites in function of the intertidal level. A study carried out during the summer of 2003 described the distributions of (1) planktonic larvae, (2) early settlers, (3) juveniles and (4) adults of soft-shell clams at three intertidal levels, in three sites within each of the great tidal regimes. No tidal regime effect was observed on all life phases studied. Similarly to 2002 results, the distributions varied between our sites in function of the intertidal level, suggesting that local factors such as small-scale hydrodynamics may drive the settlement and recruitment of clams. Our results also tend to show that recruitment of clams cannot be predicted by larval supply (planktonic veligers) nor the number of early-settlers.