THE LAST KNOWN POPULATION OF THE FRESH-WATER MUSSEL MARGARITIFERA-AURICULARIA (BIVALVIA, UNIONOIDA) - A CONSERVATION PRIORITY

In 1985 a population of Margaritifera auricularia was found in the lowe Ebro river and adjoining channels in Catalonia, Spain. This species once lived in large rivers over most of Western Europe and Morocco, but overfishing for its shell and pearls, and widespread destruction of freshwater habitats, accounted for its almost total extinction. Since its rediscovery, the freshwater mussels in the channels have been destroyed and the remaining individuals in the river itself are threatened by pollution, hydraulic works, diversion and uncontrolled collecting. No young individuals have been found. Based on low interpopulation phenotypic differentiation, inferred larval morphology, and congruent geographical and ecological distributions, it is hypothesized that the Western European sturgeon Acipenser sturio Linnaeus, 1758, an anadromous bottom-feeder, is probably the main host for this unionoid. This fish is also endangered and may be already extinct in the Ebro. The proposed conservation measures include restrictions to collecting, protection of the fish hosts and key habitats, education, establishment of captive breeding colonies, repopulation, and water quality control. © 1990.