The conservation of unionid mussels in Louisiana rivers: diversity, assemblage composition and substrate use

1. To aid in their conservation, unionid mussel assemblages were surveyed i n three relatively unstudied rivers in south-eastern Louisiana. 2. Although total species richness varied among rivers, species diversity ( as estimated both by Shannon-Weaver H ' and rank-abundance curves) was fair ly similar. 3. Assemblage composition varied among the rivers, with the Vilest Pearl Ri ver having the most dissimilar group of species. The endangered inflated he el splitter, Potamilus inflatus, was found only in the lower Amite River. 4. The most common species had size distributions skewed towards larger ind ividuals, but small individuals were collected (including the inflated heel splitter), indicating successful recruitment. 5. Mussels were more common in silt than in sand or gravel, perhaps because fine sediments are more stable through time in these river systems. 6. The greatest threat to these assemblages is gravel mining in the upper r eaches of the rivers. At the present time only rivers with endangered speci es, or that have been declared scenic rivers, have any protection from grav el mining. Copyright (C) 2001 John Wiley & Sons, Ltd.