Large spatial variability in lifetime egg production in an intertidal Baltic tellin (Macoma balthica) population

Abstract.

The extent to which it pays settling larvae of marine benthic organisms to actively select the habitat where they will spend the rest of their life can only be fully appreciated if the fitness consequences of such habitat selection processes are known. We estimated the lifetime egg production of the tellinid bivalve Macoma balthica at 11 sites over a tidal gradient in the western Wadden Sea, using a 30-year data series. The difference in individual lifetime egg production between the best sites in the lower tidal zone and the poorest sites on the high tidal flats was about a factor 10. The differences in lifetime egg production were related to differences in growth and, more importantly, survival. We argue that the large observed differences in reproductive output do not necessarily imply a lack of active habitat selection. As most animals start their last migration before final settlement from the high tidal flats, the choice may be one between a long and risky migration with a low chance of reaching the good habitat versus a more certain but poor existence on the high tidal flats.