Fish Habitat Research Articles

The “right‐to‐farm” in Lac Saint‐Pierre (Québec, Canada) floodplains: Are problem‐framing processes able to foster conservation conflict resolution?

AbstractUsing qualitative data, we investigate the impact of the problem‐framing process on stakeholder mobilization for fish habitat restoration and its influence on transforming agricultural practices in floodplains. Problem‐framing involves defining and delineating a problem to suggest practical and measurable solutions for addressing it. We are examining how the conservation conflict changes over time in Lac Saint‐Pierre (LSP), part of the St. Lawrence River Basin in Québec, Canada. Such conflicts arise when there are differing perspectives, interests, or actions regarding conservation goals and objectives. In recent decades, the LSP floodplain has undergone significant changes, particularly the conversion of perennial crops to intensive annual crops, which are deemed incompatible with the ecological needs of yellow perch. This species has experienced a notable decline in LSP since the 1990s, prompting Québec authorities to impose a moratorium on yellow perch fishing in 2012 to safeguard stocks. This moratorium has catalyzed efforts at the policy level to restore its habitat. However, it has also engendered tensions between agricultural activities and conservation endeavors aimed at restoring yellow perch habitat, constituting the conservation conflict under investigation. To investigate this issue, we adopt a post‐normal science approach characterized by reflexivity, inclusivity, and transparency in addressing epistemological and ontological uncertainties among LSP stakeholders. Our findings offer insights into stakeholders' perspectives on the problem‐framing process and its outcomes, highlighting both supportive actions enhancing the effectiveness of certain strategies among LSP stakeholders and barriers hindering their mobilization. These results underscore the importance of incorporating diverse stakeholder perspectives during the problem‐framing process to enhance the robustness of the science–policy interface.

Food web structure across basins in Lake Erie, a large freshwater ecosystem

Understanding spatial variation of aquatic food web structure and how ecosystem boundaries should be delineated is important. Here, we investigated the spatial variation in food web structure within Lake Erie across its three basins using δ13C and δ15N. Fish and lower trophic level composition were similar but differences in food web structure were observed between basins. The food web in the central basin had the smallest δ13C and δ15N range and total area based on stable isotope values by the aquatic community, likely due to chronic epibenthic hypoxia in the summer that affects fish habitat and resources. The largest δ15N range was in the east, driven by the high trophic position of lake trout present in this deepest basin. The western basin had the largest mean distance to the centroid (CD) of all three basins, indicating a large trophic diversity, probably due to high nutrient loadings and productivity. This research revealed spatial variability of food web structure in large lake ecosystems and the importance of considering smaller sub-units, such as basin, in large lakes.

A coupled machine-learning-individual-based model for migration dynamics simulation: A case study of migratory fish in fish passage facilities

The extensive development of hydropower projects has notably changed the ecohydrological conditions of fish habitats, affecting fish behavior, including habitat usage and migration, to varying extents. Understanding fish migration dynamics is essential for quantitatively assessing the impact of ecological restoration measures on migratory fish. However, no model has yet demonstrated sufficient accuracy to be considered valuable in ecological restoration engineering. To address this issue, in this article, a coupled machine-learning-individual-based model (ML-IBM) consisting of random forest (RF) and Eulerian–Lagrangian–agent method (ELAM) is constructed for predicting fish migration, aiming to find effective fish passage solutions before implementation. In this study, the passage data of ya-fish (Schizothorax prenanti) in vertical slot fishways (VSFs) is compiled to train ML-IBM to simulate fish migration in fish passage facilities. In movement prediction, the accuracy of swimming behavior classification reaches 83.4 %, and the R² for swimming speed regression exceeds 0.77. Compared with other state-of-the-art migration dynamic models, the proposed ML-IBM achieves the lowest root mean square error (RMSE) of 7.35 and a mean absolute error (MAE) of 6.26 in migration simulation results. Further, RF is used to quantitatively calculate the importance of input features. The contributions of each feature are analyzed and discussed from a hydrodynamic perspective, with the importance ranked as follows: flow velocity (FV) > turbulent kinetic energy (TKE) > total hydraulic strain (THS). This approach enhances the interpretability of the model and provides further insights into the mechanism of fish migration. The results presented in this study have significant implications for informing decision-making in the management of living resources and guiding engineering design processes.

Quarry rock reef design features influence fish assemblage structure across a systematically heterogenous restoration reef

To restore an area of temperate rocky-reef degraded by sedimentation, scour, and burial, a large quarry rock reef, the Palos Verdes Restoration Reef (PVR), was built with a heterogenous design including high relief elements intended to increase fish biomass productivity and support a diverse reef community. The replicated design features provide a unique opportunity to study the effects of reef design on fish habitat use patterns. To determine how submodule scale habitat features are associated with variation in the assemblage structure of eleven focal fish species on the PVR we conducted diver-operated stereo-video surveys on all 18 PVR modules 9–13 months after construction. The highest mean densities of most focal fish species and highest total fish densities were observed on high and medium-relief reef submodules and their adjacent ecotones positioned on the offshore sides or ends of modules. These included the most abundant species on the PVR, the zooplanktivorous Blacksmith (Chromis punctipinnis), as well as the fishery species Kelp Bass (Paralabrax clathratus) and California Sheephead (Bodianus pulcher). On the inshore side of parallel modules, the reef and ecotone transects on low and medium relief submodules exhibited the lowest total mean fish densities, and consistently lower mean focal fish species densities. Focal fish species assemblages also differed between the reef and sand-rock ecotone transects. Reef-resident planktivorous fishes likely contribute to reef primary and secondary productivity through consumer mediated nutrient transport and are an important consideration in restoration reef design. Future reef restoration designs should consider incorporating replicated heterogeneous design features including the placement of higher relief elements relative to shore and current patterns as a special consideration for providing habitat for planktivorous reef-resident fishes.

Living Shorelines Equal or Outperform Natural Shorelines as Fish Habitat Over Time: Updated Results from a Long-Term BACI Study at Multiple Sites

Living Shorelines Equal or Outperform Natural Shorelines as Fish Habitat Over Time: Updated Results from a Long-Term BACI Study at Multiple Sites

FishDet-YOLO: Enhanced Underwater Fish Detection with Richer Gradient Flow and Long-Range Dependency Capture through Mamba-C2f

The fish detection task is an essential component of marine exploration, which helps scientists monitor fish population numbers and diversity and understand changes in fish behavior and habitat. It also plays a significant role in assessing the health of marine ecosystems, formulating conservation measures, and maintaining biodiversity. However, there are two main issues with current fish detection algorithms. First, the lighting conditions underwater are significantly different from those on land. In addition, light scattering and absorption in water trigger uneven illumination, color distortion, and reduced contrast in images. The accuracy of detection algorithms can be affected by these lighting variations. Second, the wide variation of fish species in shape, color, and size brings about some challenges. As some fish have complex textures or camouflage features, it is difficult to differentiate them using current detection algorithms. To address these issues, we propose a fish detection algorithm—FishDet-YOLO—through improvement in the YOLOv8 algorithm. To tackle the complexities of underwater environments, we design an Underwater Enhancement Module network (UEM) that can be jointly trained with YOLO. The UEM enhances the details of underwater images via end-to-end training with YOLO. To address the diversity of fish species, we leverage the Mamba model’s capability for long-distance dependencies without increasing computational complexity and integrate it with the C2f from YOLOv8 to create the Mamba-C2f. Through this design, the adaptability in handling complex fish detection tasks is improved. In addition, the RUOD and DUO public datasets are used to train and evaluate FishDet-YOLO. FishDet-YOLO achieves mAP scores of 89.5% and 88.8% on the test sets of RUOD and DUO, respectively, marking an improvement of 8% and 8.2% over YOLOv8. It also surpasses recent state-of-the-art general object detection and underwater fish detection algorithms.

Drivers of variability in surf zone habitat use by sandy beach fish: Unwitting citizen scientists reveal detailed spatiotemporal patterns

Surf zones of sandy beaches are among the most heavily impacted aquatic ecosystems, yet are of critical ecological importance for inshore fish and fisheries. Knowledge of the drivers of fish habitat use in surf zones is needed across broad scales to advise conservation and fisheries management, but sampling capabilities can be limited in spatio-temporal extent and resolution. The lesser weever Echiichthys vipera is a small, benthic, venomous fish that dominates surf zone fish assemblages in Northwest Europe and inflicts painful stings on beachgoers. This study capitalises on an extensive record of E. vipera sting incidents to characterise variations in surf zone habitat use in relation to key physical environmental factors. Sting incidents, standardised by water user numbers, are used as a proxy for E. vipera abundance across 77 beaches throughout Southwest England, with 2 h resolution, from April–November 2018. General Additive Models indicated a clear peak in E. vipera abundance at spring low tides, in the afternoons of summer months, under calmer wave conditions and at higher levels of solar irradiance. Although the order of significance differed, human water users were also driven by the same variables, compounding sting interactions over time. Key physical variables did not explain spatial variation in E. vipera abundance, although there was a weak relationship with sea surface temperature, and some evidence that reflective beaches are unsuitable. Physical factors explained more spatial variation in human water users, who gathered at more dissipative beaches with greater wave heights. This detailed study of an important surf zone fish reveals clear drivers of temporal variation in habitat use, yet infers wide suitability of beaches varying in the key physical drivers of sandy shore ecology.

Freshwater exploitation at Ajvide - Pitted ware culture fishing practises investigated through laser ablation facilitated strontium isotope analyses

The importance of marine resources for the Neolithic hunter-fisher-gathers of the Pitted Ware Culture of Gotland, Sweden, is well documented through zooarchaeological analyses and diet studies of human remains. Terrestrial areas were important for living and supplementing the diet but the extent of the terrestrial territories and regions of land use for different groups is largely unknown. The presence of euryhaline species in recovered zooarchaeological assemblages indicates that freshwater fishing or fishing in the brackish estuaries of the Baltic Sea was part of the subsistence practises. To explore if the inland freshwaters of Gotland were used and, if exploited, where they were located, 18 teeth from euryhaline fish from the Pitted Ware Culture site Ajvide on Gotland were selected. The 87Sr/86Sr isotope ratios in the fish teeth were analysed using laser ablation-multi collector-inductively coupled plasma-mass spectrometry and correlated with an updated bioavailable baseline of Gotlandic water sources. Through this approach, the habitational origin of the fish was shown to primarily stem from at least six freshwater sources located in the west-central area of Gotland, in close relation to the site, with a few individuals originating from within the Baltic Sea. The study highlights the significance of ichthyoarchaeological analysis in understanding the territorial practice of past foraging societies and recommends further studies on euryhaline species to expand our knowledge of fish habitat, human resource utilization and land use.

Development of improved technologies for protecting fish from infections in aquaculture

The current intensification of marine aquaculture is inevitably associated with such environmental issues as growing infections and the need to apply antibiotic and other antimicrobial preparations. This leads to antibiotic pollution in the environment. Latest technologies aimed at preventing fish infections in aquaculture are based on the vaccination of the objects under cultivation. These technologies allow the use of antibiotics to be reduced and the balance of the microbial environment in aquaculture to be restored, eventually minimizing the negative effects of antibiotic residues on the human health. In this work, we set out to study molecular mechanisms underlying the immune response of fish to viral infections. Data on the expression of some genes of the most important aquaculture objects in Russia and China in response to infection and during its progression was obtained. The research results can be used when developing vaccines against vibriosis with the purpose of minimizing the application of medical preparations, such as antibiotics. These measures are important for maintaining healthy fish habitats and, as a consequence, the human health.

Evaluating the efficacy of ecological restoration of fish habitat in coastal waters of Lake Ontario

Ecological restoration is a common strategy applied to degraded wetlands and tributaries in large lakes. As resources are typically limited for restoration, it is essential to ensure that such efforts achieve associated goals. Using both discrete and continuous methods, we evaluated the efficacy of ecological restoration efforts on fish habitat within Canada's largest city, Toronto (Cell 2 and Embayment D of Tommy Thompson Park) relative to a control site (Toronto Islands). First, we used a long-term electrofishing dataset (i.e., discrete) to examine catch and community composition relative to restoration status. Catch for northern pike (Esox lucius) remained constant at both restoration sites, and catch of invasive common carp (Cyprinus carpio) decreased at Embayment D, indicating that exclusion barriers may be effective. Restoration was less effective for largemouth bass (Micropterus nigricans) as catches remained similar after restoration at Cell 2, but decreased within Embayment D. We also found that relative abundance for coldwater species at both restoration sites decreased post-restoration, with increases in warmwater species at Cell 2 and coolwater species at Embayment D. Next, we used a long-term acoustic telemetry dataset (i.e., continuous sampling) with three focal species: largemouth bass, northern pike, and invasive common carp. Based on telemetry, we found that restoration efficacy was species-specific, with largemouth bass present before and after ecological restoration (particularly in spring, which may be associated with spawning), but clear reductions in use of the restored areas for common carp and northern pike. Exclusion barriers, while effective at blocking common carp, appeared to also negatively influence access for northern pike. Using both discrete and continuous methods longitudinally and across both treatment and control sites provided complementary information on the efficacy of restoration works within Toronto Harbour, with electrofishing data highlighting changes in fish community composition while acoustic telemetry provided continuous information on timing and duration of habitat use.

Scenario Planning Management Actions to Restore Cold Water Stream Habitat: Comparing Mechanistic and Statistical Modeling Approaches

ABSTRACTUnder the United States Clean Water Act, states are required to periodically assess state waters to determine compliance with water quality criteria (including temperature) and then to develop total maximum daily loads (TMDLs) for impaired waters as necessary to bring them into compliance. We compared the performance of mechanistic stream temperature models (HeatSource, QUAL2K, and QUAL2Kw) applied to the mainstem of three TMDL watersheds (Middle Fork John Day, OR; Wind River, WA; South Fork Nooksack, WA) with that of spatial stream network (SSN) models applied to the full watersheds and used these to evaluate the potential effectiveness of restoration strategies. SSN models performed well with slightly lesser accuracy (RMSE = 0.47–0.87) for mainstem predictions than mechanistic models (RMSE = 0.4) but provided additional benefits to inform management, including information on spatial and temporal heterogeneity of restoration effectiveness throughout the watershed. Of the four scenarios considered (restoration of riparian zones to potential natural vegetation, channel narrowing, increasing flow by restricting irrigation withdrawals, and combined applications), riparian zone restoration was consistently the most effective in reducing temperatures at the outlet, mainstem, and throughout the watersheds. Predicted restoration effectiveness for thermal regimes varied significantly both within and among watersheds. A focus on water quality criteria exceedance only at the watershed outlet or along the mainstem reach can obscure knowledge of restoration potential for fish habitat in tributaries and headwaters, potential for creation of thermal refuge areas along the mainstem critical for maintaining migration corridors, and thermal regime heterogeneity across space and time.

Distribution of fish species in the upper Po River Basin (NW Italy): a synthesis of 30 years of data

Freshwater fish is the most diverse group of vertebrates but, unfortunately, also one of the most threatened. While some well-known, charismatic species have been subject to important conservation efforts, many others have long been neglected. This paper aims to analyse the distribution over time of seven freshwater fish species and one lamprey in the upper Po River basin (NW Italy), an important biodiversity hotspot. Six of them are native species listed in Annex II of the Habitats Directive (Lampetra zanandreai, Protochondrostoma genei, Chondrostoma soetta, Telestes muticellus, Sabanejewia larvata, and Cottus gobio), while the other two are key invasive species (Silurus glanis and Misgurnus anguillicaudatus). Data from four regional fish population monitoring campaigns carried out between 1988 and 2019 were analysed. For each species and monitoring campaign, an average Representativeness Index, measuring abundance and population structure, and an Occurrence Frequency were calculated, and then assessed for changes over the time. Of the studied species, P. genei declined the most in the last 30 years, while C. soetta and S. larvata are in a very critical situation, with very few remaining populations. T. muticellus, C. gobio and L. zanandreai seem to have declined only slightly, but their vulnerability should not be underestimated. The two invasive species, on the other hand, show a substantial increase in occurrence as well as range. While some drivers for the decline in the native species vary according to their ecological and biological characteristics, others are more general and linked to the overall degradation of the river environments: habitat alterations, loss of connectivity, excessive water abstraction, pollution, and the presence of invasive alien species. The effects of climate change, such as the rise of inland water temperatures and the alteration of hydrological cycles, must also be taken into account. Diverse and far-reaching conservation efforts are needed to improve the fish habitat and thus also protect the unique biodiversity of this region.

Anthropogenic and environmental risk factors of salmonid predation in a tidal freshwater delta

Abstract Water diversions that support agricultural and municipal use result in fish mortality through entrainment and impingement. Additionally, this infrastructure may attract both predators and prey fishes, thereby increasing predation rates and prey mortality near these anthropogenic contact points. The Sacramento–San Joaquin Delta (the Delta) in California's Central Valley is a tidal freshwater ecosystem that exports large volumes of water for municipal and agricultural use while at the same time providing valuable migratory and rearing habitat for imperilled fishes. Emigrating juvenile salmonids experience high mortality in the Delta, with predation by non‐native fishes contributing substantially. Therefore, this study had three main objectives. First, we determined if small water diversions aggregated piscivorous fishes like other similar structures in freshwater ecosystems. Second, we determined how small diversions may influence juvenile salmon predation risk in conjunction with other known predation risk factors (e.g. predator abundance, temperature and depth). Third, we assessed the predator assemblage, abundance and distribution to determine the likely predator composition in objectives one and two. Throughout the spring of 2021, we used ARIS (adaptive resolution imaging sonar; Sound Metrics) sonars to compare piscivore abundance at 30 water diversions in the north Delta to shorelines adjacent to diversions that did not contain these structures. We used predation event recorders (PERs) to assess the predation risk juvenile salmonids were exposed to, with linear distance (m) from diversions, and other predation risk factors in the north Delta. Finally, we used a boat electrofishing survey to determine the piscivore assemblage and compare spatial trends in black bass (Micropterus spp.) CPUE and relative abundance throughout these waterways. Piscivore abundance was greater near small water diversions than at adjacent shorelines and the predation risk of juvenile salmonids increased with diversion proximity. Additionally, predation risk increased with increasing piscivore abundance and decreasing water depth. The north Delta predator assemblage was dominated by black basses (Micropterus spp.), which likely drove the negative relationship of predation risk with water depth, given habitat requirements of these species. Furthermore, increasing smallmouth (Micropterus dolomieu) and spotted bass (Micropterus punctulatus) abundance in our northern study sites may have weakened temperature effects on predation, given metabolic requirements of these species. Our work demonstrated that small water diversions are likely to increase mortality of endangered salmonids, and that the north Delta predator assemblage was different than recorded by previous work in this system, changing predation risk factors. Although more work is needed to determine the population level impacts of diversions, the ubiquitous distribution of these structures warrants management solutions to reduce mortality from this source. These results indicate that in addition to entrainment and impingement, water diversions may increase mortality of small‐bodied fishes by attracting predators and elevating predation risk. Given the continual human demand for freshwater, predator–prey interactions should be considered along with entrainment and impingement when assessing intake infrastructure mitigation, especially when diversions co‐occur along migratory routes and essential habitat of imperilled fishes.

Local size structure and distribution of demersal fish in relation to sea pens and other benthic habitats in a deep-sea soft-bottom environment

Many fish species undergo ontogenetic habitat shifts as they grow to fulfill new biological, ecological and environmental requirements. While relationships between fishes and large hard-substrate cold-water corals (CWC) (e.g., Desmophyllum pertusum reefs) have frequently been studied, there are relatively fewer studies examining the relationships of fish with habitats specifically provided by smaller corals (e.g., sea pens) in soft-bottom environments. Despite this knowledge gap around soft-bottom corals, growing evidence of their importance has nonetheless justified their inclusion as conservation targets in numerous Marine Protected Areas (MPA), including the Canadian Laurentian Channel MPA. Here, we performed ROV and near-seabed drift-camera system surveys within the Laurentian Channel MPA in 2017 and 2018 to assess the influence of fish body size and habitat type on fish small-scale distribution in a low-relief deep-sea soft-sediment environment. We compared the local size structure of the four most abundant deep-sea demersal fish taxa of the channel (Redfish (Sebastes spp.), Witch Flounder (Glyptocephalus cynoglossus), Marlin-Spike Grenadier (Nezumia bairdii) and Longfin Hake (Phycis chesteri)) across one barren and five structural benthic habitats defined by the presence of nine dominant epibenthic invertebrates (actiniarians and CWCs). We used generalized additive models to identify biotic (benthic habitats) and abiotic (depth, bottom types) covariates of size for each taxon. We observed 15,381 fish within the 43.6-ha study area, of which 7,511 fish were measured. Juveniles represented 99% of all fish measured, with a notable increase in average fish size in 2018. While we did not find any associations between benthic habitats and fish life stages, the analysis revealed a significant increase in fish size within sea pen habitats for all four taxa. Conversely, we found a taxon-specific influence of bottom type on fish size for all taxa. In addition, Redfish and Longfin Hake size was positively correlated with depth. For deep-sea demersal fish taxa of the MPA, our results suggest that 1) sea pens provide nursery habitat for early-life stages, 2) fish undergo ontogenetic shifts in micro-habitat use and specialization, and 3) fish-habitat associations appear to be facultative rather than obligate. Through the use of in-situ video data, this study provided evidence that small and large fish do not use the same micro-habitats, and that sea pens contribute significantly to fish habitat despite providing less habitat heterogeneity than reef-forming scleractinians or large gorgonians. These results contribute to empirical understanding of fish-habitat relationships at different fish life stages and may inform fisheries management, as well as monitoring efforts in the MPA and other protected deep-sea environments.

Floodplains as a Suitable Habitat for Freshwater Fish: The Length–Weight Relationships and Condition Factors of Fish Inhabiting a Danube Floodplain in Croatia

When studying the well-being and fitness of ichthyofauna in a specific area, vital information comes from length–weight relationships (LWRs) and condition factor analyses and calculations. Data were collected from 2015 to 2019 in an area important for fish shelter, feeding, and spawning. Twenty four species belonging to 10 different families were identified from the total 16,895 of caught individuals, with the most abundant species being Blicca bjoerkna. The calculation of LWRs was possible for 19 species, (R2 = 0.7049–0.9998 (p < 0.05)), with the values of the mean coefficient b ranging from 2.6831 to 3.5747, indicating an overall positive allometric growth in the fish population. The results of Fulton’s and the relative condition factors showed that a total of eight species were in a relatively good condition, although the species in question varied between the two condition factors. Fulton’s condition factor showed the highest average value for Lepomis gibbosus (1.4956), while Cobitis elongatoides had the lowest (0.4739). Contrarily, the relative condition factor showed the highest average value for Silurus glanis (1.0524), and the lowest for Gymnocephalus cernua (1.0023). The lower values of calculated condition factors in some species could be attributed to sampling being conducted during the colder months of autumn and winter. Future studies should include seasonal sampling in order to achieve a better understanding how various abiotic factors impact the condition factors of these fish species. Nevertheless, this research provided valuable data on the status of the fish population in the floodplain and could be used as a guideline for designing future ichthyofauna studies in this area.

Geospatial Mapping and Health Status of Some Important Ornamental Fish Habitats of Upper Assam, India

To conserve and manage water resources, it is crucial to create a record of water bodies and their catchments, which can be accomplished through digitized maps. The research focused on five rivers - River Dibru, River Sessa, River Burhidihing, River Brahmaputra, as well as two wetlands of Upper Assam - Maguri Beel, and Mer Beel. These water bodies were chosen based on their abundant fishery resources. Each selected water body was divided into three segments, and one sampling station from each segment was selected for monitoring water quality and recording fish species. The distribution of the catchment area was analyzed in the form of raster maps and geomorphology maps. Based on fish landings, the water bodies were identified and classified, and fish samples were collected through regular field surveys. Over the period from January 2021 to December 2022, eleven physicochemical parameters of the selected water bodies were recorded seasonally to assess the health status of each water bodies. Similarly, the health status and growth coefficient of each fish specimen was done. Water parameters were mostly within the standard limits and demonstrated only a narrow range of seasonal variation. In the studied water bodies, 49 ornamental fish species representing 32 genera under 18 families and 8 orders were found. Among the water bodies, River Dibru had the highest number of ornamental fish species at 46. The order Cypriniformes was dominant in all the studied sites.

Discharge and sediment load modeling using rating curve-based missing data management

ABSTRACT Hydrological models are vital for water management to determine in-stream flow, irrigational water, domestic water supply, and biodiversity conservation. This study formulates a hydrological model with a novel approach for streamflow and sediment load in the QGIS-supported Soil and Water Assessment Tool for the Halda River catchment, a unique ecological habitat for natural carp spawning and freshwater sources. The daily simulation uses an innovative stage–discharge relationship technique from available 15-day interval flow data. The model evaluation parameters R2 values 0.80 and 0.62, and NS values 0.81 and 0.61 for calibration and validation of streamflow suggested excellent agreement in the seasonal cycle and most of the monsoon peak flow. The streamflow/precipitation ratio indicates a significant influence of groundwater through infiltration. The baseflow shows a decreasing trend. The sediment load based on suspended sediment concentration at a downstream location is 1,625 tons/day. On the contrary, the model prediction is 30 times lower. The scattered sediment load data support the model estimate by considering relatively lower intervention or land use change in its upstream. This model provides a baseline for daily flow and sediment load for scenario modeling (e.g., climate change, land use change) for environmental flow estimation of the fish habitat, freshwater supply, irrigation, and salinity intrusion.

Fish habitat models for a future of novel riverscapes.

Multiple anthropogenic forces have pushed river ecosystems into undesirable states with no clear understanding of how they should be best managed. The advancement of riverine fish habitat models intended to provide management insights has slowed. Investigations into theoretical and empirical gaps to define habitat more comprehensively across different scales and ecological organizations are crucial in managing the freshwater biodiversity crisis. We introduce the concept of novel riverscapes to reconcile anthropogenic forcing, fish habitat, limitations of current fish habitat models, and opportunities for new models. We outline three priority data-driven opportunities that incorporate the novel riverscape concept: fish movement, river behavior, and drivers of novelty that all are integrated into a scale-based framework to guide the development of new models. Last, we present a case study showing how researchers, model developers, and practitioners can work collaboratively to implement the novel riverscape concept.

Integrating aquatic species, assemblage, and habitat climate change vulnerabilities into a watershed-scale decision support framework

Climate change is increasingly recognized as a serious threat to ecological systems, particularly freshwater systems. As a result, climate adaptation planning is more common in natural resource management. Because conservation resources are limited, decision support tools can help managers prioritize actions. We created the Species and Habitat-based Ecological Decision Support tool (wtrSHEDS) for conservation managers by integrating two distinct indices: one biologically based on aquatic watershed-scale species assemblages and the other a habitat climate change vulnerability index. To do this, we evaluated 60 crayfish and fish species in West Virginia, USA, using the NatureServe Climate Change Vulnerability Index under an A1B emissions scenario. The species vulnerability assessment results indicated that most species we assessed are vulnerable to climate change. Four species of fish and two species of crayfish had extremely high vulnerability due to their dependence on a specific hydrological cycle, sensitivity to barriers, and reproductive dependence on a thermal niche. Aggregating species at the watershed scale (8-digit hydrological unit code [HUC]) using an adapted weighted sum indicated which assemblages were the most and least vulnerable to climate change. Secondly, we created a unique habitat vulnerability index using the established Northeast Association of Fish and Wildlife Agencies habitat vulnerability index and an index of land cover vulnerability from the Forecast Scenario model’s land cover change projections under the A1B emissions scenario to incorporate potential synergistic impacts of land use. Land cover projections were reclassified based on the assumption that developed land would have a higher potential to interact with climate change than forested lands synergistically. We combined the two habitat indices at the watershed scale (HUC 8) and performed a Hot Spot Analysis to 1) combine the assemblage and habitat vulnerability indices and 2) identify watersheds of conservation priority. This assessment methodology illustrates a means of identifying priority conservation areas in West Virginia that utilize pre-existing data, can be modified to suit management needs, and, therefore, one that managers across regions can readily apply to their system.

Unseen riverine risk: Spatio-temporal shifts of microplastic pollution and its bioavailability in freshwater fish within the Ikopa River urban system.

Growing concern over microplastic pollution, driven by their widespread accumulation in the environment, stresses the need for comprehensive assessments. This study investigates the spatial and temporal distribution of microplastics in the Ikopa River (Antananarivo - Madagascar), which flows through a densely populated area, and examines their correlation with contamination levels in local fish species. By analyzing upstream and downstream stations across wet and dry seasons, only a notable increase in microplastic concentration downstream during the wet season was observed, ranging from 138.6 ± 9.0 to 222.0 ± 24.5 particles m-3, with polyethylene-co-vinyl acetate being the predominant polymer at 62.3 ± 5.13% of the total sampled polymers. This distribution underlines the impact of urban activities on pollution levels. Fish species, gambusia and Nile tilapia, were assessed for microplastic occurrence in gills and gastrointestinal tracts. Higher contamination rates were found in gambusia, enlightening the influence of feeding behaviour and fish habitat on microplastics contamination. Ingestion of microplastics directly from the water column was evident in both species, with the detection of high-density plastics such as polytetrafluoroethylene and polyvinyl chloride suggesting likely sediment contamination. This research highlights the widespread contamination of aquatic environments and its direct impact on local wildlife, pointing to a clear requirement for effective pollution management strategies.