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

Abstract

Shovelnose 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.

Factors associated with Paddlefish (Polyodon spathula) restoration success in Oklahoma

“…Although this research focused on restoration potential as it relates to spawning substrate and forage availability, ultimately we infer that periphery influences more system specific such as turbidity, predation or fish escapement compounding with limited spawning substrate or forage may determine restoration success or failure. This is a theme in many restoration initiatives, for instance while the overarching life history needs in this study of spawning substrate and forage availability were present for Shovelnose Sturgeon in restoration efforts in sections of Big Horn River, Wyoming, insufficient drift distances of larvae resulted in failed recruitment as larvae settled into the hypoxic reservoir transition zone (Hogberg et al., 2021). Therefore, it is important when considering reintroduction success that having a complete understanding of the species life history and the causes of extirpations will better predict reintroduction success in individual systems.…”