Heeft de korfmossel Corbicula ook predators in de Rijn? II. Schelpreparatie

Shell repair was used to study the presence of shell-crushing predators on Corbicula in the Rhine. Shell repair was observed in about 4% of the shells of Corbicula fluminalis and C. fluminea collected along the shores of the river Rhine. Shell repair was observed mainly near the umbo. This indicates (failed) predation of shells of 6Ð10 mm length, and therefore the presence of predators on small specimens of Corbicula. The low number of broken shells (1.4%), and the low percentage of repaired shells, suggests shell-crushing predators not to be a very important factor in mortality of Corbicula. The large amount of intact articulated shells in the drift along the shores, often still with dried remnants of the animal inside, indicates low oxygen content, high summer temperatures, desiccation during the low waterlevel of the Rhine this summer and washing away to be the probable causes of their mortality.