Examining Alternative Water Management Strategies to Support Rio Grande Silvery Minnow Conservation Within and Across Years

Rio Grande Silvery Minnow (RGSM) are currently constrained to only 5% of their historic range, and their persistence is threatened by highly altered and impaired habitat conditions (Bestgen and Platania 1991). These habitat conditions have resulted from reduced spring and summer flows due to natural variability and anthropogenic water development and extraction, which have resulted in substantial geomorphic changes (Swanson et al. 2011). Successful conservation of this endangered species will require determination of how available flows can be managed to provide conditions supporting growth, reproduction, and survival of RGSM within and across a variety of water years. Previous research has identified that years with large spring high flow events and years with higher summer base flows support greater densities of RGSM during fall surveys (Dudley and Platania 2007; Archdeacon 2016; Walsworth and Budy 2021). However, given that years with large spring high flows also tend to have greater summer base flows, it remains unclear whether spring or summer flows (or both) are more critical to successful conservation of RGSM

Trophic Structure of Apex Fish Communities in Closed Versus Leaky Lakes of Arctic Alaska

Despite low species diversity and primary production, trophic structure (e.g., top predator species, predator size) is surprisingly variable among Arctic lakes. We investigated trophic structure in lakes of arctic Alaska containing arctic char Salvelinus alpinus using stomach contents and stable isotope ratios in two geographically-close but hydrologically-distinct lake clusters to investigate how these fish may interact and compete for limited food resources. Aside from different lake connectivity patterns (‘leaky’ versus ‘closed’), differing fish communities (up to five versus only two species) between lake clusters allowed us to test trophic hypotheses including: (1) arctic char are more piscivorous, and thereby grow larger and obtain higher trophic positions, in the presence of other fish species; and, (2) between arctic char size classes, resource polymorphism is more prominent, and thereby trophic niches are narrower and overlap less, in the absence of other predators. Regardless of lake cluster, we observed little direct evidence of arctic char consuming other fishes, but char were larger (mean TL = 468 vs 264 mm) and trophic position was higher (mean TP = 4.0 vs 3.8 for large char) in lakes with other fishes. Further, char demonstrated less intraspecific overlap when other predators were present whereas niche overlap was up to 100% in closed, char only lakes. As hydrologic characteristics (e.g., lake connectivity, water temperatures) will change across the Arctic owing to climate change, our results provide insight regarding potential concomitant changes to fish interactions and increase our understanding of lake trophic structure to guide management and conservation goals

Effective Conservation of Desert Riverscapes Requires Protection and Rehabilitation of In-Stream Flows With Rehabilitation Approaches Tailored to Water Availability

Desert riverscape rehabilitation practitioners must contend with compounding effects of increasing human water demand, persistent drought, non-native species establishment, and climate change, which further stress desert riverine ecosystems such as rivers in the Colorado River basin, United States. Herein, we provide our perspective on the importance of natural flows, large floods in particular, for successful conservation and rehabilitation of riverscapes. We present ideas developed from our experience with rehabilitation projects across multiple desert tributary rivers with varying levels of habitat degradation and water abstraction. We propose spatially extensive measures such as protection of in-stream flows, tailoring rehabilitation efforts to available annual water availability, and working with nature using low-tech process-based techniques to more completely address the mechanisms of habitat degradation, such as flow reduction and vegetation-induced channel narrowing. Traditionally, rehabilitation efforts in the Colorado River basin take place at relatively small spatial extents, at convenient locations and, largely focus on reducing non-native plant and fish species. We suggest that we need to think more broadly and creatively, and that conservation or recovery of natural flow regimes is crucial to long-term success of almost all management efforts for both in-stream and riparian communities

A Lota lota consumption: trophic dynamics of non-native Burbot in a valuable sport fishery

Unintentional and illegal introductions of species disrupt food webs and threaten the success of managed sport fisheries. Although many populations of Burbot Lota lota are declining in the species’ native range, a nonnative population recently expanded into Flaming Gorge Reservoir (FGR), Wyoming–Utah, and threatens to disrupt predator–prey interactions within this popular sport fishery. To determine potential impacts on sport fishes, especially trophy Lake Trout Salvelinus namaycush, we assessed the relative abundance of Burbot and quantified the potential trophic or food web impacts of this population by using diet, stable isotope, and bioenergetic analyses. We did not detect a significant potential for food resource competition between Burbot and Lake Trout (Schoener’s overlap index = 0.13), but overall consumption by Burbot likely affects other sport fishes, as indicated by our analyses of trophic niche space. Diet analyses suggested that crayfish were important diet items across time (89.3% of prey by weight in autumn; 49.4% in winter) and across Burbot size-classes (small: 77.5% of prey by weight; medium: 76.6%; large: 39.7%). However, overall consumption by Burbot increases as water temperatures cool, and fish consumption by Burbot in FGR was observed to increase during winter. Specifically, large Burbot consumed more salmonids, and we estimated (bioenergetically) that up to 70% of growth occurred in late autumn and winter. Further, our population-wide consumption estimates indicated that Burbot could consume up to double the biomass of Rainbow Trout Oncorhynchus mykiss stocked annually (\u3e1.3 × 105 kg; \u3e1 million individuals) into FGR. Overall, we provide some of the first information regarding Burbot trophic interactions outside of the species’ native range; these findings can help to inform the management of sport fisheries if Burbot range expansion occurs elsewhere

Movement Patterns of Resident and Translocated Beavers at Multiple Spatiotemporal Scales in Desert Rivers

Wildlife translocations alter animal movement behavior, so identifying common movement patterns post-translocation will help set expectations about animal behavior in subsequent efforts. American and Eurasian beavers (Castor canadensis; Castor fiber) are frequently translocated for reintroductions, to mitigate human-wildlife conflict, and as an ecosystem restoration tool. However, little is known about movement behavior of translocated beavers post-release, especially in desert rivers with patchy and dynamic resources. We identified space-use patterns of beaver movement behavior after translocation. We translocated and monitored nuisance American beavers in desert river restoration sites on the Price and San Rafael Rivers, Utah, USA, and compared their space use to resident beavers after tracking both across 2 years. Resident adult (RA) beavers were detected at a mean maximum distance of 0.86 ± 0.21 river kilometers (km; ±1 SE), while resident subadult (RS) (11.00 ± 4.24 km), translocated adult (TA) (19.69 ± 3.76 km), and translocated subadult (TS) (21.09 ± 5.54 km) beavers were detected at substantially greater maximum distances. Based on coarse-scale movement models, translocated and RS beavers moved substantially farther from release sites and faster than RA beavers up to 6 months post-release. In contrast, fine-scale movement models using 5-min location intervals showed similar median distance traveled between RA and translocated beavers. Our findings suggest day-to-day activities, such as foraging and resting, were largely unaltered by translocation, but translocated beavers exhibited coarse-scale movement behavior most similar to dispersal by RSs. Coarse-scale movement rates decreased with time since release, suggesting that translocated beavers adjusted to the novel environment over time and eventually settled into a home range similar to RA beavers. Understanding translocated beaver movement behavior in response to a novel desert system can help future beaver-assisted restoration efforts to identify appropriate release sites and strategies

Consequences of Didymo Blooms in the Transnational Kootenay River Basin

Stream habitat changes that affect primary consumers often indirectly impact secondary consumers such as fishes. Blooms of the benthic algae Didymosphenia geminata (Didymo) represent one such habitat change known to affect stream macroinvertebrates. However, the potential indirect trophic impacts on fish consumers via modifications to their diet are poorly understood. The overall goal of this project was to determine if Didymo blooms in streams of the Kootenay River basin of British Columbia and Montana affect the condition and growth of fishes, and to see whether trophic mechanisms were responsible for any observed changes. We therefore quantified the diet, condition, and growth rate of trout, charr, and sculpin in a paired, Didymo vs. reference study, during the summer of 2018 and across a gradient of Didymo abundance in 2019. In the 2018 study, trout diets were 81% similar despite obvious differences in the composition of macroinvertebrate assemblages between the Didymo and reference streams. Trout abundance was higher in the stream with Didymo, but the amount of invertebrates in the drift was higher in the stream without Didymo. Growth rate and energy demand by individual trout was similar between the two streams. In the 2019 study, across a gradient of coverage, Didymo abundance was correlated only with the percent of aquatic invertebrates in trout diets and did not affect diets of charr or sculpin. Variation in fish condition was low across study streams. Thus, Didymo blooms may impact trout diets to a small extent, but we found no evidence this impact translates to changes in condition or growth. The relationship of fish abundance to Didymo blooms bears further study, but we found no obvious trophic mechanisms that would explain any differences. We suggest future studies prioritize research on potential impacts during winter months and on species with limited mobility that may be most greatly impacted by Didymo

Angler Catch Rates, Opinions, and Abiotic Variable Relationships in the Lower Logan River, Utah

Summer base flows for rivers are critical for maintaining water quality, healthy fish populations, and a functional aquatic ecosystem. Low summer base flows can increase water temperatures and lower dissolved oxygen levels. These conditions can cause Brown Trout (Salmo trutta) energetic stress and result in lower angler catch. The goal of this study was to determine if low river flows and higher water temperatures influence angler catch rates of Brown Trout on the lower Logan River, Utah and to better understand angler use of the lower river. We performed a creel survey on approximately 6.4 km of the lower Logan River from 1 April to 31 October 2019 to calculate mean monthly angler catch rates. We used continuous collection of stream temperature and flow from a river gage within the survey reach to calculate monthly means. Total Brown Trout caught were 1,481 and total angling effort was 2,147 hours for an overall catch rate of 0.7 fish per hour (fph) for the survey period. The highest angler catch rate (1.2 fph) was in June with the highest mean monthly discharge (16 m3/s) and a mean monthly water temperature of 9.6 °C. The lowest angler catch rate (0.41 fph) occurred in September with a mean monthly discharge of 2.12 m3/s and a mean monthly water temperature of 11.2°C. We found a positive correlation between flow rates and angler catch rates (R2 = 0.37), and a negative correlation between water temperatures and angler catch rates (R2 = 0.42), although neither were statistically significant. Our data suggest that even on a higher-than-average runoff year, angler success is impacted by low summer base flows. Maintaining increased river flow during typical summer low-flow time periods could increase angler catch rates and, ultimately, provide even greater satisfaction with this fishery. We also determined educational signage and outreach could be extremely influential, as anglers knew little about regulations of the fish community in general

Keeping It Classy: Classification of Live Fish and Ghost PIT Tags Detected With a Mobile PIT Tag Interrogation System Using an Innovative Analytical Approach

The ability of passive integrated transponder (PIT) tag data to improve demographic parameter estimates has led to the rapid advancement of PIT tag systems. However, ghost tags create uncertainty about detected tag status (i.e., live fish or ghost tag) when using mobile interrogation systems. We developed a method to differentiate between live fish and ghost tags using a random forest classification model with a novel data input structure based on known fate PIT tag detections in the San Juan River (New Mexico, Colorado, and Utah, USA). We used our model to classify detected tags with an overall error rate of 6.8% (1.6% ghost tags error rate and 21.8% live fish error rate). The important variables for classification were related to distance moved and response to monsoonal flood flows; however, habitat variables did not appear to influence model accuracy. Our results and approach allow the use of mobile detection data with confidence and allow for greater accuracy in movement, distribution, and habitat use studies, potentially helping identify influential management actions that would improve our ability to conserve and recover endangered fish

Conservation, Restoration, and Monitoring Plan for the Lower White River, Utah

In this report we present a conservation, restoration and monitoring plan for the lower White River, a major tributary of the Green River. The plan is intended to help guide conservation, restoration and management of the lower White River over the next several decades and is also developed as an adaptive management plan to facilitate learning. The recommended conservation and restoration actions are intended to maintain and enhance native riparian vegetation and instream habitat for native desert fishes including federally endangered Colorado Pikeminnow (Ptychocheilus lucius), federally endangered Razorback Sucker (Xyrauchen texanus), Speckled Dace (Rhinichthys osculus), Bluehead Sucker (Catostomus discobolus), Flannelmouth Sucker (C. latipinnis), and Roundtail Chub (Gila robusta). ~~Many mammals, amphibians, migratory birds, and raptors that use the riparian zone or migrate through the riverscape are also anticipated to benefit from the plan. The recommended conservation and restoration actions are based on the best available information regarding the current ecological and geomorphic conditions and restoration recovery potential. We prioritized reaches for conservation and restoration actions using expert opinion and field validation, riparian vegetation density and instream and riparian habitat condition and complexity data. We recommend an experimental design for implementation of conservation and restoration actions. Combined with monitoring, the experimental design is aimed at identifying the most successful conservation and restoration actions for maintaining complex instream habitat and a healthy native riparian community