Natural Recruitment Potential of a Reintroduced Shovelnose Sturgeon Population in the Bighorn River, Wyoming

Abstract

AbstractShovelnose Sturgeon Scaphirhynchus platorynchus were extirpated from the Bighorn River, Wyoming during the 20th century after the construction of two main‐stem dams and the resulting modifications to fish passage and flow and thermal regimes. The species was reintroduced to the river between 1996 and 2020, but nothing was known about how these fish used the river and whether they could sustain themselves without consistent stocking. Radio telemetry during 2015–2018 identified at least two putative spawning locations 95.6 and 139.5 river kilometers upstream from a reservoir transition zone. Temperature and velocity data suggest that most of the drifting larvae will have insufficient fluvial habitat to complete their drift stage and are likely to enter the Bighorn Lake transition zone. Benthic dissolved oxygen concentrations in the reservoir transition zone were low enough to cause recruitment reduction or failure for drifting larvae that reach this habitat. Future monitoring will determine whether this population persists, but this study highlights the importance of understanding species life history and the causes of extirpations to better predict reintroduction success.