Exploitation trajectory of a declining fauna: a century of freshwater mussel fisheries in North America

Freshwater mussels (Bivalvia: Unionidae) have been an economically valuable biological resource in North America since the mid-1800s. Although the industries based upon mussel harvest are quite distinct from one another, the trends apparent in harvest statistics are remarkably similar among each successive harvest era. Whether fished for freshwater pearls, button production, or cultured pearl production, market factors have driven commercial harvests while the life history and ecology of mussels have been largely ignored. Annual yields of freshwater mussels are declining throughout the United States and catch per unit effort (CPUE) has declined dramatically in some of the most important American mussel fisheries. Harvest statistics indicate that mussel populations are dangerously depleted due to the erosion of the latest industry based upon their harvest. It seems likely that the exhaustive harvests of both the distant and recent past, coupled with habitat loss and degradation, have left North American unionid mussel populations at levels insufficient to support the substantial harvests consistently demanded by industry. This century-long exploitation trajectory provides valuable lessons about the mechanisms of fisheries collapse that are necessary to ensure the sustainable management of aquatic resources.