Life-History Data on the Virtually Unknown Margaritifera auricularia

Abstract

Published information on the declining and widely distributed freshwater pearl mussel Margaritifera margaritifera (L.) is currently flourishing in the scientific literature, being the centre of attention of most invertebrate conservation treatises (Young et al. this Vol.). The case of the other European species of the genus, the giant naiad Margaritifera auricularia (Spengler 1793; Fig. 8.1) is completely different. It was relatively abundant in large rivers in western Europe (Iberian Peninsula, France, Italy, England, Germany) and Morocco (Preece et al. 1983). Indeed, recent data on its former distribution in Spain (Araujo and Moreno 1999) demonstrate that it lived in several rivers other than the Ebro (northeast Spain), which is the only one known currently containing populations of this vanishing species. All available biological data on this nearly extinct species date from the past 3 years from one rediscovered population of about 2000 individuals in the Canal Imperial de Aragón (Imperial Canal), an old canal of the Ebro built in the 18th century, where the species has found one of its last refuges (Araujo and Ramos 1998a).