Publicly Available Data Reveal Information Gaps in Freshwater Mussel–Fish Interactions and Co‐Occurrence Critical to Biodiversity Conservation

Freshwater systems only cover a small fraction of the Earth's surface; however, they support a remarkable diversity of species, with over one‐third currently imperilled. Freshwater mussels, with more than 65% of species threatened or endangered, rank among the most imperilled animal groups globally. Mussels support ecosystem processes and depend on specific fish hosts for successful larval development. However, identifying suitable host fish primarily relies on laboratory trials that may not accurately reflect natural conditions, especially if host ranges do not overlap with those of the mussels.

In this study, we investigate co‐occurrence patterns between mussels and their host fish across the Southeastern US, an aquatic biodiversity hotspot, by integrating information from two publicly accessible data sources: the Freshwater Mussel Host Database and museum occurrence records spanning 1800–2016. We developed quantitative metrics to assess different aspects of host‐mussel interactions that enabled us to identify catchments and species with incomplete ecological data.

To illustrate the value of this resource, we combined metrics into a composite prioritisation score and created an interactive tool to highlight species and catchments with the greatest research needs. Among the 229 mussel taxa assessed, 25 species exhibited less than 80% habitat overlap with their known fish hosts, with 52% of those classified as vulnerable, imperilled, or critically imperilled. Our analysis also found that in four catchments, fewer than 50% of mussel species had hosts that have been identified.

These results demonstrate the need for refined host identification and the integration of species distributions into conservation efforts. All datasets and code used in this analysis, as well as the interactive tool, are publicly available to support reproducibility and broader use. By aligning conservation strategies with ecological co‐occurrence, we can better support the recovery of imperilled mussel populations and promote the conservation of freshwater ecosystems across the Southeastern United States and beyond.