Freshwater pearl mussel in Finland—current status and future prospects

Abstract

Information on the present distribution and status of the threatened freshwater pearl mussel Margaritifera margaritifera populations in Finland was updated. The status of the populations was classified into seven categories which are viable, maybe viable, non-viable/partly viable, dying-out, almost extinct, probably extinct, and extinct. The main criteria for judging the viability class were the population size and proportion of juvenile mussels. According to calculated estimate 1.7% populations were viable, 8.5% maybe viable, 40.2% non-viable/partly viable, 14.5% dying-out, 30.8% almost extinct, and 4.3% probably extinct. The present number of rivers with M. margaritifera in Finland is 117.