Using Habitat Quality Indicators to Evaluate the Success of Freshwater Habitat Improvements
Tanya A. Lemieux tanyalemieux@cmail.carleton.ca, Sean J. Landsman, Jonathan D. Midwood, Karen Smokorowski, Christina M. Davy, Jacob W. Brownscombe, Ken M. Jeffries, and Steven J Cooke
“Despite freshwater ecosystems being critically important, they have been severely degraded such that freshwater biodiversity losses have been widely documented. To mitigate this loss, many attempts to improve freshwater habitats have been undertaken using various techniques such as those related to restoration and rehabilitation. Assessing whether these efforts are effective is necessary to not only support habitat and species recovery, but also to inform future initiatives. However, such initiatives are challenged by funding constraints, timeline limitations, and lack of standardized evaluation methods, resulting in a need to define relevant monitoring strategies. High quality habitat is essential for population persistence making habitat quality a relevant indicator of the success of freshwater habitat improvement efforts. Additionally, habitat quality indicators are more relatable to the habitat itself and thus more indicative of long-term success than metrics currently being used. Herein we describe key indicators of habitat quality and illustrate why such measures are useful assessment tools for evaluating the success of freshwater habitat improvements. Based on our synthesis, we outline methods that can be used to describe habitat quality for animals such as metrics of behaviour, bioenergetics, ‘omics’, food webs, and biotic indices. We also outline challenges associated with assessing habitat quality and make suggestions to help overcome them. We then share considerations for evaluating the success of habitat improvement initiatives using habitat quality indicators including how to define success, select appropriate spatial and temporal scales, and consider the tiers of evidence provided by the different indicators. To conclude, we present two case studies to further illustrate the practical application (and challenges) of using habitat quality indicators to assess the effectiveness of freshwater habitat improvement initiatives.”
Joachim Pander, Christoffer Nagel, Juergen Geist
“Habitat quality, diversity and connectivity are key variables governing biodiversity patterns, but existing conservation and restoration strategies hardly consider their important interlinkages in river networks. In order to develop best practice river network restoration strategies, fish diversity and the spatio-temporal occurrence of target species of conservation in relation to abiotic habitat conditions were assessed in the alpine River Inn network comprising main stem, tributaries and confluences. Fish sampling was carried out by standardized electrofishing during spring, summer and autumn. In addition, important physicochemical variables were collected to interlink abiotic habitat characteristics with the fish community patterns. Differences in the physicochemical habitat conditions between the main stem and the tributaries were particularly evident in turbidity, electrical conductivity and temperature. This was also reflected in seasonal distribution patterns of fishes which differed between tributaries and main stem, even at small spatial scales. Cyprinids such as common nase and barbel were generally found more frequently in the tributaries where they successfully reproduced. In contrast, cold-water adapted species such as grayling, brown trout and European bullhead were detected much more frequently in the River Inn main stem, mostly as juveniles. Across species, distribution patterns were strongly driven by spawning migration into tributaries in spring and back-drift of larvae and juveniles to the main stem between summer and autumn. Consequently, the diverse habitats of interconnected river networks are key in sustaining the life cycles of diverse and healthy fish populations, and they can provide refuge areas increasing the resilience of such systems. The findings are directly relevant for restoration projects in large alpine rivers to address two primary aspects: Firstly, to create heterogeneous habitat structures that reflect the diverse life cycle requirements of target species, and secondly, to improve multidimensional river network connectivity.”
Shayla Triantafillou, Ellen Wohl
“Modification of river corridors, particularly deforestation and the removal of large wood, has greatly altered the abundance and influence of large wood in most rivers in the temperate latitudes. The conceptual framework of large wood process domains can assist in both directing research and facilitating large wood-related management and restoration in rivers. Large wood process domains are spatially or temporally distinct portions of a river network or region with distinct processes of wood recruitment, transport, and storage. Previous research has shown wood to be unevenly distributed across space and time. We use a data set of logjam distribution density (# of channel-spanning logjams/100 m length of channel) in 304 spatially distinct reaches of mountain streams in the Colorado Front Range, and up to 11 years of repeat measurements at some reaches, to (a) statistically evaluate whether a priori designated process domains for logjam distribution density are distinctly different and (b) evaluate the sensitivity of process domain delineations to spatial and temporal sample size. Our results indicate that the major spatial controls on logjam process domains for logjam distribution density in the Southern Rockies are drainage area, reach morphology, and wildfire disturbance history. Greater logjam distribution densities were present in wide reaches and undisturbed catchments. Using subsets of the data set composed of under 100 reaches created similar results. The relationship between geomorphic and hydrologic characteristics and their ability to describe logjam distribution density was minimally affected when using fewer than 10 years of data.”
Xian-bing Zhang, Shang Huang, Yu-peng Hu, Geng Li, Wen-jie Li & Sheng-fa Yang
“River ecosystems are vital to Earth’s biogeography and environmental health by facilitating material cycling, energy transfer, and information exchange. However, human activities, including hydraulic engineering, land use changes, industrial and agricultural expansion, and overfishing, have significantly disrupted natural river morphology and ecological patterns. These interventions have altered the river’s physical and chemical properties, resulting in biodiversity loss and ecosystem services degradation, prompting increased global attention to river ecological management. This review analyzes the major threats to river ecosystems, emphasizing their collective and interconnected impacts on ecosystem degradation. Current international methods for ecological assessment and restoration are critically evaluated, noting their effectiveness at small to medium scales but limitations when applied to entire river systems. To address these challenges, the review proposes an integrated approach combining macroscopic ecological restoration measures with microscopic analyses of river feedback mechanisms. This holistic perspective considers both upstream and downstream activities, as well as complex interactions between human interventions and river ecosystems. The paper aims to provide new insights for river ecology research, inform policymaking, and suggest future research directions. By advocating for a more comprehensive understanding of river ecosystems, this review contributes to the development of sustainable and effective river governance practices.”
A Conceptual Framework and Methods for Studying the Connectivity of Fishes
Jordanna N. Bergman1 | Jessica A. Robichaud1 | Jasper McCutcheon2 | Michael T. Booth3 | Brendan Campbell4 |
Grace A. Casselberry5 | Cienna R. Cooper6 | Bronwyn M. Gillanders7 | Lucas P. Griffin8 | Edward Hale4,9 | Luc LaRochelle1 |
Karen J. Murchie10 | Mary Peacock11 | Reid G. Swanson12 | Simon D. Stewart13,14 | Ryan. J. Woodland15 | Daniel P. Zielinski12 |
Steven J. Cooke1 | Morgan L. Piczak16,1
“Connectivity is a multifaceted concept that has important implications for the management and conservation of marine and freshwater fishes. We developed a conceptual framework that encompasses multiple, interrelated categories of connectedness, including landscape (e.g., structural, functional) connectivity and ecological (e.g., trophic, genetic, demographic) connectivity, that together shape the flow of organisms, energy and information across ecosystems. We also synthesised six key methods that can be used to study connectivity of fishes: (1) telemetry, including satellite, acoustic, radio and passive integrated tran[1]sponders (PIT), (2) mark-recapture, (3) environmental tracers, including stable isotopes and otolith-microchemistry, (4) genet[1]ics, (5) community structure analysis and (6) emerging technologies and tools (e.g., remote sensing and artificial intelligence). For each method, we describe the categories of connectivity it can assess and provide real-world examples where they have been effectively used. We also identify limitations of each method. This article highlights the diverse and evolving toolbox of methods used to assess fish connectivity, underscoring the need for continued collaboration, innovation and integration of new approaches to refine our understanding and address remaining challenges in this critical area of aquatic ecology and fisheries management.”
Carley E. Winter 1, Clare L. Kilgour 1 3, Colin J. Brauner 1, Chris M. Wood 1 2, Patricia M. Schulte
“Road salt, primarily sodium chloride (NaCl), is frequently used as a de-icer during cold seasons. In the Vancouver Lower Mainland (VLM) region of British Columbia, Canada, road salt is contaminating local streams where Pacific salmon spawn. The provincial acute water quality guideline is 600 mg L-1 Cl–, yet road salt contamination is resulting in pulses of salinity estimated to exceed this guideline by over 11-fold. In the VLM, the spawning and subsequent rearing period of coho salmon (Oncorhynchus kisutch) directly overlaps with these pulses of salinity. This study investigates the lethal and sublethal effects of road salt pulses on coho salmon by simulating an environmentally realistic pulse of road salt at different stages of development. We exposed coho embryos to a 24-h salt pulse at five environmentally relevant salt concentrations at <1 h post-fertilization or at 50% hatch. To investigate effects on fertilization success, we used a 5-min salt exposure at the time of fertilization. Following salt exposures, coho were returned to freshwater to rear until swim-up to assess survival and presence of deformities. There was no effect of salt exposure on fertilization, but the <1 h post-fertilization exposure group was sensitive to a salt pulse, as there was significant mortality, persistent ionoregulatory disruptions, and increased deformities. Upon hatching, exposed embryos exhibited a decrease in body length and larger yolk sac volume, suggesting that the early salt pulse disrupted embryonic development. Our research highlights an urgent need for improved road salting practices to protect developing coho salmon.”
Yu Xin, Lin Liu, Shao-Hua Chen, Quan-Bao Zhao, Yu-Ming Zheng
“Appropriate riverbed substrates, as nature-based engineering components, are critical for enhancing nutrient mitigation and ecosystem sustainability in urban rivers. However, their role in regulating hydrologically mediated nutrient fluxes and biofilm functions remains unclear, limiting substrate-optimized design for urban river restoration. This study integrated machine learning modeling, scenario simulations, and metagenomic analysis to quantify substrate-driven interfacial nutrient removal efficiencies and uncover microbial regulation mechanisms. A back propagation neural network could accurately predict interfacial ammonium and total organic carbon removal efficiencies (RMSE: 0.59-6.92 mg/(L·h·m2), R2: 0.66-0.97), with retention time, temperature, dissolved oxygen, and nutrient load identified as key predictors. Building upon the model-predicted scenario results, analysis of similarity tests confirmed that substrate type significantly influenced interfacial nutrient removal efficiencies (R > 0.05, P < 0.001). Scoring metrics demonstrated fine sand (1295) and gravel (1281) gained higher total scores than other substrates (1110-1182), indicating higher interfacial nutrient removal capacities. Metagenomic analyses revealed that these differences were driven by divergence in microbial functional potential. Substrate type selectively enriched functional genes related to nitrogen and carbon cycling (R > 0.18, P < 0.05), with gravel microcosms showing significantly higher gene abundance (8.00 × 10-4-2.08 × 10-3), despite similar community compositions governed by stochastic assembly (R² > 0.84). Topological analysis revealed that redundancy of functional gene network significantly influenced ammonium removal efficiency (P < 0.05), with fine sand and gravel enhancing ammonium removal, while lower clustering coefficients in artificial filler and gravel microcosms significantly promoted total organic carbon removal. This study suggested that fine sand and gravel should be more effective riverbed substrates for enhancing interfacial nutrient removal in urban river restoration.”
Erich T. Hester, Kenneth Ham, Brenda Pracheil, Heida Diefenderfer, Ryan Harnish
“Rivers are essential to humans and ecosystems, and can generate renewable energy. Yet hydropower dams substantially alter water and sediment flows, affecting river ecosystems including keystone species such as salmonids. Mitigation can include modification of dams and their operation, hatchery production, predator and harvest management, water and temperature management, and habitat restoration. Yet challenges enhancing and even measuring salmonid populations, realization of the importance of large-scale interventions, and concerns about acceleration of climate change effects create a need to reassess the future of science and practice. Here we consider the role of river restoration as a tool for mitigation of hydropower impacts to anadromous fish. We use the Columbia River Basin (CRB) in North America as a model system, and view mitigation strategies in terms of their ability to overcome limitations to salmonid population growth. We review the state of the science regarding the interaction of hydropower and river restoration, and their effects on salmonid populations in the CRB, and identify important areas for future research. A key challenge is measuring and modeling both environmental and biological conditions and processes at both small and large scales simultaneously, which is critical to prioritizing actions in the CRB. We also identify promising tools for monitoring and numerical modeling. Such research and development is best paired with robust coordination among researchers, government regulators, and practitioners. Such a multi-scale approach amplified by broader coordination is ultimately relevant to a range of large-scale environmental challenges beyond the CRB.”
Bryce D. Finch1 | Johan L. Aarnink1 | Andrés Iroumé2 | Katherine B. Lininger3 | Susan Hilton4 | Stanley Gregory5 | Virginia Ruiz-Villanueva
“Large wood (LW) entrainment and transport observations of naturally occurring wood in rivers are critical for understanding wood dynamics. However, they remain limited and sparse, primarily originating from single-site studies. As a result, broader spatial or temporal variability of wood dynamics may not be adequately captured. We compiled a database of tracked, natural pieces of wood from 11 low-order and relatively steep streams in the Chilean Andes, Swiss Alps, United Kingdom and United States. From decades to single-year studies, we gathered 59,739 observations of tracked wood, which all include at least a recorded length and transport distance. River characteristics varied according to channel width, less than 5 m to wider than 15 m, and gradient, between < 0.02 and > 0.04 m/m. The meta-analysis enabled us to calculate probabilities and identify general patterns. Wood mobilization varied significantly interannually, reflecting the complex interplay between flood events and wood storage. Overall, a small proportion of tagged wood moved during study periods, primarily during events associated with return periods exceeding 10 years. Most mobile pieces travelled less than 1 km, and longer distances had relatively low probabilities, typically occurring during high-magnitude flood events associated with return periods over 10 years. Results showed that large wood mobility in rivers is generally infrequent and highly variable, influenced by a combination of wood characteristics, river size and flood magnitude. Understanding variability can help inform risk-based flood hazard planning, river management and river restoration projects implementing large wood. Future studies should expand upon the current dataset.”
Markéta Hauferová1 | Paul F. Hudson2 | Achim Häger2
“Benthic macroinvertebrates are indicators of water quality and riparian ecosystem health. Their abundance and distribution in streams are associated with river basin environmental factors, including stream biotic and abiotic fluvial processes. We ex[1]amined benthic macroinvertebrate diversity and abundance in relation to large wood (LW) and pool-riffle morphology along the Geul River (NL), a small meandering river typical of European landscapes. Restoration since 1998 that includes remean[1]dering and beaver (Castor fiber) reintroduction (2002 to 2004) has enhanced the riparian ecosystem. Field sampling was de[1]signed to determine abundance and taxa composition of benthic macroinvertebrates, differentiating between sites with LW and without (control) and between pools and riffles. Additional variables included velocity, depth, bed material and canopy cover. Macroinvertebrate diversity to measured environmental factors was evaluated with alpha and beta diversity indices and diver[1]sity t-tests. Relationships between LW and environmental variables on community composition were assessed using nonmetric multidimensional scaling (NMDS) and analysis of similarities (ANOSIM). Thirty-one macroinvertebrate taxa were identified, most at the Genus and Family level. Gammaridae (freshwater shrimp) was dominant across all sites. Macroinvertebrate diversity was significantly higher in riffles than pools, while taxa richness was higher for LW in comparison to control sites. Invertebrate community composition was not significantly affected by LW or measured environmental variables. Despite stream restoration, the index of Ephemeroptera, Plecoptera and Trichoptera (EPT) taxa amounted to 33%, indicating degraded water quality. At a basin scale management authorities should strive to reduce agricultural runoff, especially silt inputs. At the channel-reach scale the pool-riffle morphology and design of effective LW structures should be a guiding management goal for attaining riparian health consistent with targets of the EU Water Framework Directive.”