Modelling changes in trout habitat following stream restoration

Abstract

Stream restoration was implemented on the Upper Arkansas River near Leadville, Colorado, to improve brown trout (Salmo trutta) populations. Metals pollution and channel disturbance associated with historic mining, land use, and water development degraded aquatic and riparian habitat. Changes in instream habitat quality following restoration were investigated with a before-after-control-impact study design. Baseline, asbuilt, and effectiveness surveys were conducted in 2013, 2014, and 2016, respectively. Two-dimensional hydrodynamic modelling with River2D was used to estimate weighted usable area (WUA) for adult, juvenile, fry, and spawning brown trout across a range of flows. WUA was calculated from habitat suitability curves for velocity, depth, and channel substrate. Foraging positions (FP) and habitat heterogeneity were also evaluated as indices of habitat quality. All results were analysed with analysis of variance. At impact sites, WUA increased by 12.2% from 2013 to 2014 but decreased by 10.2% from 2014 to 2016, whereas FP increased by 24.8% from 2013 to 2014 but decreased by 26.1% from 2014 to 2016. Spawning habitat increased 53.3% from 2014 to 2016 at impact sites. The 15.4% increase in depth variability from 2013 to 2016 indicates that habitat heterogeneity was enhanced at impact sites. No changes in WUA, FP, or habitat heterogeneity were observed at control sites. Although changes in WUA and FP suggest that initial habitat improvements were not sustained, increased spawning habitat and depth heterogeneity suggest otherwise. Our results highlight the value of monitoring strategies that utilize multiple lines of evidence to evaluate restoration effectiveness, inform adaptive management, and improve restoration practices.

From Gold Mining to Gold Medal Fishery: Evaluating the Fishery Response to Stream Restoration on the Upper Arkansas River, Colorado

“…As there were no migration barriers within the study site that would restrict fish movement, higher densities could be driving fish to seek out available habitat at both control and impact sites. Habitat modeling indicated that restoration activities had improved spawning habitat (Richer et al 2019), which could have affected recruitment and overall population density. These observations suggest that the scale of the restoration project may have affected density observations regardless of site type and that the change in density across all sites could in fact be related to restoration activities.…”

“…The average W r following restoration (96) was still <100, but improved fish condition suggests that habitat conditions may have improved despite the overall increase in Brown Trout density. Habitat modeling demonstrated that restoration treatments improved habitat heterogeneity and foraging positions for Brown Trout (Richer et al 2019), which may have contributed to improved fish condition by enhancing ecological heterogeneity (Palmer et al 1997) and energy acquisition (Pope et al 2010). Improved fish condition could also be indicative of improved water quality throughout the California Gulch Superfund Site (Clements et al 2010).…”

“…Some of the upstream control sites (EF-1, AR-1) appear to be functioning as juvenile rearing grounds, as indicated by the high densities and complete absence of quality-sized Brown Trout. Interannual variability in watershed hydrology may also have contributed to the significance of discharge in the density and biomass models as habitat suitability within the project reach declined significantly with increasing discharge (Richer et al 2019). Decreased habitat suitability during higher flows could have motivated fish to seek out more favorable habitat conditions in upstream or downstream reaches.…”

“…The primary goal of restoration was to improve instream aquatic habitat and increase Brown Trout populations, including a 10% improvement in fish population and health metrics in restored areas by year 5 after construction (Stratus 2010b). Other monitoring targets included instream structures (Richer et al 2017), riparian vegetation (Kulchawik and Bledsoe 2013;Cubley et al, in press), benthic macroinvertebrates (Clements et al 2010;Pomeranz 2015;Wolff et al 2019), and habitat quality (Richer et al 2019). As evidence of a fish population response to restoration activities may take five or more years (Hunt 1976;Binns 1994;Roni et al 2018), this study represents the initial 5-year, postrestoration evaluation of the project.…”

Relationship between Morphological Characteristics and Quality of Aquatic Habitat in Mountain Streams of Slovakia

“…This relationship can be modelled, which allows a qualitatively higher level for a wide range of water management activities. Habitat modelling in fish ecology [8] provides one of the most comprehensive tools for scrutinizing the river potential to provide a favourable platform for river ecosystems and simultaneously proposes measures to improve the habitat [9]. Instream flow models connect a physical habitat model predicting hydraulic changes to a biological model predicting the response of fish to an altered velocity and depth.…”