Article: Size-frequency and growth-ring analyses of Mytilus edulis and Cardium edule, and their palaeoecological significance

The population growth patterns of living Mytilus edulis and Cardium edule from the Firth of Forth, Scotland, are analysed. Fossil communities and death assemblages derived from the living populations are also investigated and the size-frequency patterns of living and dead shells compared. The use of growth-ring analysis as a tool in palaeoecology is considered.Size-frequency criteria used in the discrimination of fossil communities and death assemblages are critically re-examined. It is argued that mortality rates among preservable young in many cases may be much lower than has hitherto been assumed. Symmetrical size-frequency distributions in fossil species, therefore, need not necessarily indicate size sorting. A distinction is drawn between age-mortality rates derived from living animals and size-mortality rates determined from fossils.