Patterns from the Freshwater Mussel Host Database

Freshwater fishes and mussels are diverse and abundant constituents of freshwater ecosystems, and the interactions between these globally distributed assemblages are important to many aspects of aquatic ecology. The life cycle of most freshwater mussels includes an obligate parasitic larval stage on fishes, and thus fishes are essential to maintaining mussel populations. The Freshwater Mussel Host Database, maintained by the Illinois Natural History Survey, is an extensive, open-access resource aimed at standardizing and synthesizing published host–parasite observations between mussels and their vertebrate hosts. Given the size, scope, and widespread use of this critical resource, we sought to provide a high-level review of the database to identify data strengths, biases, opportunities, and emergent patterns. Strengths include mussel–host association records for 386 host species and 185 mussel species from 6 continents. There is a strong geographic bias toward North American taxa and a bias toward the inclusion of physiological hosts identified in a lab rather than ecological hosts used in the wild. Identifying mussel–host relationships in natural settings is a clear opportunity for improving knowledge in understudied regions and taxa, but allocating resources and support to do this work will be needed. We consider the strong reliance on physiological host observations as a potential threat to conservation planning, and greater focus on in situ interactions has the potential to develop more nuanced, population-level recommendations aimed at specific conservation outcomes. The Freshwater Mussel Host Database provides a strong foundation to launch coordinated efforts by fish and mussel conservation and management groups to better understand and manage freshwater mussels, freshwater fish, and their interactions.