Historical data reveal fish assemblage shifts in an unregulated prairie river

Abstract

Wyoming's Powder River is considered an example of a pristine prairie river system. While the river hosts a largely native fish assemblage and remains unimpounded over its 1,146‐km course to the Yellowstone River confluence, the hydrologic regime has been altered through water diversion for agriculture and natural gas extraction and there has been limited study of fish assemblage structure. We analyzed fish data collected from the mainstem Powder River in Wyoming between 1896 and 2008. Shifts in presence/absence and relative abundance of fish species, as well as fish assemblage composition, were assessed among historical and recent samples. The recent Powder River fish assemblage was characterized by increased relative abundances of sand shiner Notropis stramineus and plains killifish Fundulus zebrinus, and decreases in sturgeon chub Macrhybopsis gelida. Shifts in fish species relative abundance are linked to their reproductive ecology with species with adhesive eggs generally increasing in relative abundance while those with buoyant drifting eggs are decreasing. Assemblage shifts could be the result of landscape level changes, such as the loss of extreme high and low flow events and changing land use practices.

Long‐term patterns of fish community structure and decline in native species in a Colorado River reservoir, Arizona and Nevada

“…Our study supported the notion that trajectories of fish communities in large, altered rivers often are directional and more extreme (Whitten and Gibson-Reinemer 2018) compared with those of fish communities that are composed primarily of native species in smaller and less-altered stream systems (e.g., Matthews et al 2013). Hydrologic variability has been found to a critical component in structuring fish community composition in small and large rivers (Gido et al 2010;Kiernan and Moyle 2012;Senecal et al 2015). Fluctuating water levels in Lake Mohave have been shown to strand and desiccate Razorback Sucker eggs (Minckley and Gustafson 1982), but predation by introduced piscivores has been identified as the main reason for the decline of native fishes in the lower Colorado River (Marsh et al 2015).…”

“…Hydrologic variability has been found to be a critical component in structuring fish community composition in small and large rivers (Gido et al 2010; Kiernan and Moyle 2012; Senecal et al 2015). Fluctuating water levels in Lake Mohave have been shown to strand and desiccate Razorback Sucker eggs (Minckley and Gustafson 1982), but predation by introduced piscivores has been identified as the main reason for the decline of native fishes in the lower Colorado River (Marsh et al 2015).…”

“…Similarly, natural disturbance events such as large floods can cause directional changes in fish community structure, with return to its preflood state (Matthews et al 2014). However, constant anthropogenic perturbations, flow modifications, or nonnative species introductions can exceed ecological thresholds and cause communities to directionally change over time, with no return to its previous state (Gido et al 2010; Senecal et al 2015; Whitten and Gibson‐Reinemer 2018). Directional community trajectories can partially or completely return to their former structure (Gardner and Wear 2006; Muehlbauer et al 2011).…”

A new composite abundance metric detects stream fish declines and community homogenization during six decades of invasions

“…We expand on the work of Buckwalter et al (2018) by analysing local (stream segment) and basin-wide (landscape) trends in native and non-native fish abundance, thereby describing a related but distinct aspect of species spread and decline. Studies providing information on both landscape-and population-level aspects of spread and decline of most resident species in a given drainage are relatively rare, despite the fact that both analyses may be important for understanding the conservation status of native species, overall changes in regional fish assemblages, and the potential for impacts of nonnative species (Lyons et al, 1998;Senecal et al, 2015). During successful invasions, non-natives usually undergo predictable periods of establishment within the initial area of introduction, signified by increases in local abundance, followed by geographic spread to nearby locations; research suggests that different characteristics of invaders may be favourable during each of these invasion phases (Marchetti et al, 2004).…”

Catch Rates for Sturgeon Chubs and Sicklefin Chubs in the Upper Missouri River 2004–2016 and Correlations With Biotic and Abiotic Variables

“…For Sturgeon Chub, the Powder River (a tributary to the Yellowstone River) historically serves as a stronghold for the species (Stewart 1981;Werdon 1992;USFWS 1993a), with this tributary delineated as a range-wide Sturgeon Chub refuge (Hoagstrom et al 2011). Senecal et al (2015) identified a substantial decrease in Sturgeon Chubs in the Powder River since 1980, with the species noted as rare by 2008. By contrast, Stagliano (2014) indicated that Sturgeon Chubs in the Powder River rebounded from low collection frequencies during 2005-2011 (present at 13% of sites) to increased occurrence during 2012-2013 (present at 65% of sites).…”