Unionid Monitoring and Biodiversity Observation (UMBO): Monitoring data for freshwater mussels (Bivalvia: Unionidae) in seven southwestern Ontario, Canada watersheds (1999-2024)

Fisheries and Oceans Canada, in partnership with Environment and Climate Change Canada and the Ausable Bayfield Conservation Authority, has established the Unionid Monitoring and Biodiversity Observation (UMBO) network to track species-specific mussel abundance and population trajectories across seven watersheds in southern Ontario: Ausable River, Bayfield River, Grand River, Maitland River, Saugeen River, Sydenham River, and Thames River. The dataset includes results from 51 monitoring sites: 8 sites in the Ausable River, 1 site in the Bayfield River, 7 sites in the Grand River, 6 sites in the Maitland River, 4 sites in the Saugeen River, 13 sites in the Sydenham River, and 12 sites in the Thames River. Each river was sampled on a 5-10 year cycle, with Ausable River and Sydenham River sites having been sampled 3 times, and sites in all other rivers sampled twice.

Methods
A systematic sampling approach with three random starts was employed by a minimum three person search crew. Generally, each site was divided into 25 3 m x 5 m (15 m2) blocks although occasionally additional blocks/quadrats were sampled. Within each block, three 1 m2 quadrats were excavated. The quadrats were selected randomly before the survey began and the same three quadrats were excavated in each block at a site. Each quadrat was searched, beginning at the downstream end of the quadrat using three different techniques: (1) visual scan with the naked eye; (2) visual search with a viewing box; and, (3) excavation 10 to 15 cm into the substrate. After each method was used within a quadrat, all of the mussels found were identified, sexed visually (if sexually dimorphic), and measured (maximum length in millimeters) using Vernier calipers. When the quadrat was fully excavated, the removed substrate was replaced and the mussels were returned to the 1 m2 area from which they were collected.  Data are available for 33 species representing 133 unique subpopulations (species x river).