Fragmentation and fish passage: can fishways mitigate discontinuities in Great Plains fish communities?

Master of ScienceDepartment of BiologyKeith B. GidoFishways are a common tool for mitigating the effects of habitat fragmentation on fish communities, but their utility in low-gradient, sand-bed rivers of the Great Plains is not well studied. The Lincoln Street Fishway on the Arkansas River became operational in 2015 and was built specifically to pass small-bodied threatened fishes. We used a combination of surveys up-and downstream of the barrier and tagging experiments to test the ability of fishes to move into and through the fishway. Differences in fish community structure up- and downstream of the dam were more pronounced prior to the construction and operation of the fishway. In particular, Emerald Shiner Notropis atherinoides was absent from collections upstream of the dam before fishway construction, but commonly collected upstream in 2015 and 2016 surveys. Surveys within the fishway structure revealed 29 species, or 74% of the total species captured during our study were using the fishway. To further quantify fishway passage, we used a VIE experiment to assess if fish marked downstream of the fishway moved into or upstream of the fishway. Although we did not recapture marked fish upstream of the fishway, some marked individuals moved into the fishway. Finally, we conducted a PIT tag experiment to evaluate short distance movements within the fishway for three species of small-bodied minnow and were able to document upstream movement across a gradient of flows through the fishway. Results from our study illustrate the potential for fishways to mitigate the effects of habitat fragmentation on small-bodied fishes in sand-bed rivers

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

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

Understanding the Effects of Climate Change via Disturbance on Pristine Arctic Lakes—Multitrophic Level Response and Recovery to a 12-Yr, Low-Level Fertilization Experiment

Effects of climate change-driven disturbance on lake ecosystems can be subtle; indirect effects include increased nutrient loading that could impact ecosystem function. We designed a low-level fertilization experiment to mimic persistent, climate change-driven disturbances (deeper thaw, greater weathering, or thermokarst failure) delivering nutrients to arctic lakes. We measured responses of pelagic trophic levels over 12 yr in a fertilized deep lake with fish and a shallow fishless lake, compared to paired reference lakes, and monitored recovery for 6 yr. Relative to prefertilization in the deep lake, we observed a maximum pelagic response in chl a (+201%), dissolved oxygen (DO, −43%), and zooplankton biomass (+88%) during the fertilization period (2001–2012). Other responses to fertilization, such as water transparency and fish relative abundance, were delayed, but both ultimately declined. Phyto- and zooplankton biomass and community composition shifted with fertilization. The effects of fertilization were less pronounced in the paired shallow lakes, because of a natural thermokarst failure likely impacting the reference lake. In the deep lake there was (a) moderate resistance to change in ecosystem functions at all trophic levels, (b) eventual responses were often nonlinear, and (c) postfertilization recovery (return) times were most rapid at the base of the food web (2–4 yr) while higher trophic levels failed to recover after 6 yr. The timing and magnitude of responses to fertilization in these arctic lakes were similar to responses in other lakes, suggesting indirect effects of climate change that modify nutrient inputs may affect many lakes in the future

Assessment of Potential Augmentation and Management Strategies for Razorback Sucker \u3cem\u3eXyrauchen texanus\u3c/em\u3e in Lake Mead and Grand Canyon: A 2021 Science Panel Summary

Razorback Sucker Xyrauchen texanus is a large-bodied, long-lived species endemic to the Colorado River Basin. This species historically ranged throughout the basin from the Colorado River delta in Mexico to Wyoming and Colorado. Currently, the species persists ,in a small portion of its historical range with the help of intensive management efforts including augmentation. Recruitment to adult life stages is extremely limited in the wild, but is documented consistently in Lake Mead. Research and monitoring efforts in Lake Mead are ongoing since 1996 and have recently expanded to include the Colorado River inflow area and portions of lower Grand Canyon. Despite evidence of recruitment, the current population size in Lake Mead and Grand Canyon is believed to be small (data) and susceptible to stochastic effects. This raised interest in the potential to augment the population to prevent loss of genetic diversity and increase abundance and distribution in general, as well as explore recruitment bottlenecks. To address critical uncertainties surrounding this management option and to brainstorm other potential options, a Planning Committee and Steering Committee made up of representatives of state (Arizona, Nevada), tribal (Hualapai Tribe, Navajo Nation), and federal (Bureau of Reclamation, National Park Service, and U.S. Fish and Wildlife Service) management agencies convened an Expert Science Panel (ESP; 2021), to consider augmentation and management strategies for Razorback Sucker in Lake Mead and Grand Canyon. The purpose of this report is to summarize those findings

Movement, habitat use, and early life history of fishes in novel river-reservoir complexes

Doctor of PhilosophyDepartment of BiologyKeith B. GidoReservoirs and associated river-fragments are novel ecosystems now common across the globe. Riverine habitats have been transformed and fragmented by dams creating mixed lotic-lentic habitats used as introduction points for non-native species. This has resulted in altered habitats and fish assemblages consisting of species that do not share an evolutionary history. The Colorado River basin is fragmented by dams that create a complex of river fragments and reservoir habitats used by native fishes, such as razorback sucker (Xyrauchen texanus). Low survival of early life stage (ELS) razorback sucker in the Colorado River Basin, USA is thought to cause a recruitment bottleneck, but conservation efforts are limited by a complete mechanistic understanding of causal factors. I used a combination of lab and field studies to examine potential limiting factors contributing to the lack of recruitment by razorback sucker, assessed distribution patterns of the fish assemblage along the San Juan River inflow to Lake Powell, and evaluated movement potential across the entire upper Colorado River basin including between reservoir and riverine habitats. To explore discrepancies in survival of razorback sucker compared to other co-occurring sucker species, I used museum-cataloged fish specimens collected from the San Juan River, Utah to quantify trophic resource use of co-occurring ELS suckers. I evaluated diet diversity and composition using gut content and stable isotope analysis, expecting high overlap in diets among sucker species. Razorback sucker had the lowest diet richness. Although they were smaller and less developed than the other two species, differences in diet item occurrence across sizes and species reflect differences in resource acquisition among ELS suckers that might be related to recruitment bottlenecks. In the next chapter, I assessed species distributions along a 20 km reach of the San Juan River-Lake Powell inflow with the prediction that fish abundance would increase upstream with increasing energy inputs. I identified strong patterns in total number of species and individuals captured with both increasing towards the river inflow by systematically sampling shoreline habitats with trammel nets. Changes in assemblage structure were driven mainly by increases in relative abundance of benthic omnivores, including razorback sucker, towards more transitionary and riverine habitats, but also by increases in predatory species, such as striped bass (Morone saxatilis). River-reservoir inflow areas might provide high-quality feeding areas for both benthic omnivores and piscivores. Lastly, I assessed movement potential of adult razorback sucker across reservoir and river habitats in the upper Colorado River basin using a multi-agency tagging database. Given unimpeded access to upstream riverine habitats, I expected fish to move long distances and readily exchange between riverine and lacustrine habitats. Of 722 fish captured in the Colorado River inflow, 261 were re-encountered and 107 of those were subsequently encountered upstream in the Colorado and Green river systems, or in the San Juan River inflow, with 11 individuals moving at least 586 km. The proportion of fish moving between lacustrine and riverine habitats was estimated in the San Juan River inflow. Within a year of being captured in the reservoir, 29% and 20% of fish in 2017 and 2018, respectively, were detected 30 km upstream in the San Juan River. In 2016-2017, we translocated a total of 303 fish upstream of a 6 m tall waterfall into the San Juan River. Generally, fish did not reside long in the river as 80% were re-encountered downstream of the waterfall within a year. These data show long-distance movements are not limited to a few individuals and illustrate how large river fish can maintain population connectivity in highly altered ecosystems. Managing for the maintenance of diverse movement syndromes (e.g., river-resident versus transient fish) will likely increase population resilience to environmental change. Collectively, this work contributes to an increased knowledge of the ecology and life history of a highly imperiled species and sheds light on fish assemblage use of novel riverine and reservoir habitats that are widespread across the globe

Predicting Thermal Responses of an Arctic Lake to Whole-Lake Warming Manipulation

We investigated how lake thermal processes responded to whole lake warming manipulation in an arctic lake through observations and numerical modeling. The warming manipulation was conducted by artificially heating the epilimnion as a proxy for climate warming. We performed numerical modeling with an improved lake scheme based on the Community Land Model (CLM). We simulated a control run (CTL) without warming and a warming manipulation simulation (WARM). Results indicated WARM accurately captured observed temperatures where water stratification was extended in time, and water stability was strengthened. Two additional sensitivity tests with different warming onset dates and of the same warming duration showed that earlier warming onsets are predicted to make the water column more stable and less easily mixed relative to a later onset of warming. The results provide a more complete understanding of lake thermal processes in arctic freshwater lake systems and how they will respond to predicted future warming

Trophic niches of native and nonnative fishes along a river-reservoir continuum

Abstract Instream barriers can constrain dispersal of nonnative fishes, creating opportunities to test their impact on native communities above and below these barriers. Deposition of sediments in a river inflow to Lake Powell, USA resulted in creation of a large waterfall prohibiting upstream movement of fishes from the reservoir allowing us to evaluate the trophic niche of fishes above and below this barrier. We expected niche overlap among native and nonnative species would increase in local assemblages downstream of the barrier where nonnative fish diversity and abundance were higher. Fishes upstream of the barrier had more distinct isotopic niches and species exhibited a wider range in δ15N relative to downstream. In the reservoir, species were more constrained in δ15N and differed more in δ13C, representing a shorter, wider food web. Differences in energetic pathways and resource availability among habitats likely contributed to differences in isotopic niches. Endangered Razorback Sucker (Xyrauchen texanus) aggregate at some reservoir inflows in the Colorado River basin, and this is where we found the highest niche overlap among species. Whether isotopic niche overlap among adult native and nonnative species has negative consequences is unclear, because data on resource availability and use are lacking; however, these observations do indicate the potential for competition. Still, the impacts of diet overlap among trophic generalists, such as Razorback Sucker, are likely low, particularly in habitats with diverse and abundant food bases such as river-reservoir inflows

Can Fishways Mitigate Fragmentation Effects on Great Plains Fish Communities?

Fishways are a common tool for mitigating the effects of habitat fragmentation on fish, but their utility in low-gradient, sand-bed rivers of the Great Plains is not well studied. The Lincoln Street Fishway on the Arkansas River became operational in 2015 and was built specifically to pass small-bodied threatened fishes. We compared current and historical surveys up- and downstream of the barrier to test the effect of the fishway on community structure and conducted tagging experiments to test the ability of fishes to move into and through the fishway. Differences in community structure and species richness between communities up- and downstream of the dam were reduced following construction of the fishway. Surveys within the fishway revealed 74% of species from the sampled community were using the fishway. Fishes marked with VIE downstream of the dam were recaptured in the fishway, qualitatively showing that small-bodied fishes could move into and upstream within the fishway. We further quantified upstream movement for three species of small-bodied minnow tagged with PIT tags during manipulations of flows through the fishway. Our results illustrate the potential for fishways to mitigate the effects of habitat fragmentation on fishes in sand-bed rivers.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author