Freshwater mussels are critical for healthy ecosystems, but the status of many species is unknown. Many mussel species are declining due to invading species, withdrawing water, rising water temperatures, and changing land-use practices, but threats are unknown for many species. Two species of freshwater mussels co-exist in the Bear River drainage in Wyoming and are of management concern: California floater (Anodonta californiensis) and Western pearlshell (Margaritifera falcata). Both species are in decline in other parts of their range. Our goal is to understand the life cycle and potential constraints on the California floater and Western pearlshell mussels in the Bear River. We assessed four stages of development to identify potential constraints for each species. We collected water samples to identify larval mussels, sampled fish to look for glochidia attached to their host, and conducted snorkel surveys to assess juveniles and adults in 2023 and 2024. We detected <20 glochidia from the water column, observed glochidia on the gills of 61 fish, discovered 14 potential juvenile mussels from sediment surveys, and detected 1,398 Western pearlshell and 180 California floater mussels during snorkel surveys. New host fish species the native mussels are using were identified, including bluehead sucker (Catostomus discobolus), mountain sucker (Catostomus platyrhynchus), and mountain whitefish (Prosopium williamsoni). Our project provides novel information on the distribution, abundance, reproduction, and potentially limiting factors for the California floater and Western pearlshell mussels within the Bear River watershed and will inform management decisions locally, regionally, and beyond.