Distribution of cockles Cerastoderma edule in the Eastern Scheldt: habitat mapping with abiotic variables

On the basis of maps of environmental variables and annual surveys, a habitat map was constructed for the cockle Cerastoderma edule, a commercially exploited dominant suspension feeder in the Eastern Scheldt (The Netherlands). The results obtained show that the distribution of cockles can be described using emersion time and current velocity. Salinity does not play a significant role, even though low salinities are known to limit the distribution of cockles in other areas. The response to current velocity was as expected, but the response to emersion contradicted results from other studies. These responses cannot be explained as the result of competition for space with the recently expanded Pacific oyster population, because Pacific oysters are most common in habitats that are unsuitable for cockles. Possible explanations for cockles¿ apparent preference for settling in areas with relatively long emersion times are high predation pressure or instability of the sediment around low water level.