Density, Apparent Survival, and Local Population Size of Louisiana Pigtoe (Pleurobema riddellii) in the Neches River, Texas

Most North American unionids are imperiled to some degree, including the Louisiana Pigtoe, Pleurobema riddellii, which is currently under review for listing U.S. Endangered Species Act. Understanding a species' population dynamics, spatial and temporal variation in survival, density, recruitment, size, vital conservation, but this information lacking P. riddellii. We conducted mark–recapture study estimate apparent size of riddellii within 25-m2 area at three sites (75 m2 total) Neches River, Texas from 2014 2019. used program MARK evaluate POPAN models estimating parameters. collected total 392 unique individuals over 5-yr period observed recapture rate averaged 55.6%. The most parsimonious model indicated that survival varied temporally, temporally spatially, both entry probability (recruitment) spatially. Apparent 83.3% ± 3.4% (SE)/yr, overall across was 429 (overall density = 5.7/ m2), recruitment 6.3%/yr. High relatively high presence lack changes suggest these populations stable. throughout long section river, localized patches higher abundance, suggests River large river global stronghold species.