Pearly mussels Unionoidea live in lakes rivers and streams around the world These bivalves play important roles in freshwater ecosystems and were once both culturally and economically valuable as sources of food pearls and mother of pearl Today however hundreds of species of these mussels are extinct or endangered David L Strayer provides a critical synthesis of the factors that control the distribution and abundance of pearly mussels Using empirical analyses and models he assesses the effects of dispersal habitat quality availability of fish hosts adequate food predators and parasites He also addresses conservation issues that apply to other inhabitants of fresh waters around the globe and other pressing issues in contemporary ecology