River Fish Community Research Articles

Estimation of fish assessment index based on ensemble artificial neural network for aquatic ecosystem in South Korea

Fish assessment index (FAI) is commonly used to perform ecological health assessments of fish communities in rivers. However, the estimation of this index is difficult, considering the complexity of relationships among water quality, water quantity, and hydrologic properties. In this study, we propose an ensemble artificial neural network (EANN) based on various hydrological and environmental variables, and their correlation, to improve the FAI estimation for the ecological health assessment of streams and water resource management. The optimal input variables of the model were determined through correlation analyses. These values were used to train the ANN model using the Levenberg-Marquardt algorithm. The EANN model was structured with varying number of neurons and ensemble sizes. This model provides better generalization and model performance than the single ANN model for estimation. The proposed model was applied to 143 monitoring sites across Han, Nakdong, Geum, Yeongsan, and Seomjin rivers in South Korea. The 5- and 10-fold cross-validation approaches were used to evaluate the results of the model based on the Nash criterion, relative root mean squared error, and relative mean bias. For performance comparison, support vector machine (SVM) was used as the other feasible alternative because this method shows good performance in regression analysis and solves problems mathematically, unlike other machine learning algorithms. The results indicate that EANN is suitable for solving large complex problems and provides better FAI estimates than the SVM, which can be used to manage ecological conditions.

城镇化背景下深圳典型流域鱼类群落特征及驱动因子研究

PDF HTML阅读 XML下载 导出引用 引用提醒 城镇化背景下深圳典型流域鱼类群落特征及驱动因子 DOI: 10.5846/stxb202106071510 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 深圳市主要河流水生态监测与评价项目（2019-07-233） Characteristics of fish communities and driving factors under urbanization in typical river basins in Shenzhen City, China Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:理解城镇的快速发展对河流鱼类群落结构的影响，是城镇河流科学管理和生物多样性保护的关键基础。研究于2019年丰水期（8月）和枯水期（11月），选取我国城镇化典型城市-深圳域内两个处于不同城镇化程度的代表性流域，应用多重统计方法比较分析了流域间鱼类群落结构的差异，并探讨了驱动鱼类群落变异的关键环境要素。结果发现，城镇化程度高的观澜河流域其鱼类种类组成、优势类群、生物多样性指数与城镇化程度低的坪山河流域有明显差别。具体表现为：城镇化程度高的流域土著敏感种类如异鱲、吸鳅等几近消失，优势类群为外来入侵耐受种类，其物种多样性显著低于城镇化程度低的流域（P<0.05）。同时，外来鱼类在城镇河段其数量占比平均达92.5%，广泛分布于深圳城镇河流中。在环境因素方面，城镇化程度高的观澜河流域水体理化指标总氮、总磷、氨氮、化学需氧量、生化需氧量、高锰酸盐指数均显著性高于城镇化程度低的坪山河流域（P<0.05）。基于Bray-Curtis距离的冗余分析显示：城镇用地占比和总氮是影响观澜河和坪山河流域鱼类群落差异的主要因素。城镇化进程中河流生境的改变已影响到土著鱼类的生物多样性。因此，推动以恢复土著鱼类生物多样性的河流生态治理与保护是今后水生态目标管理的重要方向。 Abstract:Understanding impacts of rapid urbanization on structure of river fish communities is the key basis for scientific management and biodiversity conservation for urban rivers. We selected two representative basins with different degrees of urbanization in the typical urbanized city, Shenzhen City, China. Field sampling was conducted in both wet (August) and dry (November) seasons in 2019. We compared and analyzed the differences of fish communities between the two basins using the multiple statistical methods, and explored the key environmental factors driving the variations of fish communities. Results showed that species composition, dominant species, and biodiversity of fish in the highly urbanized Guanlan River Basin were significantly different from those in the less urbanized Pingshan River Basin. In particular, the sensitively indigenous fish species such as Schistura fasciolatus and Parazacco spilurus disappeared while the invasive tolerant species were the dominant species in the highly urbanized basin. Fish biodiversity was significantly lower in the highly urbanized basin than the less urbanized basin (P<0.05). Meanwhile, non-native fish species had spread rapidly in urbanized rivers of Shenzhen City, which accounted for more than an average of 92.5% in the urbanized river sites. For environmental factors, total nitrogen, total phosphorus, ammonia, chemical oxygen demand, biochemical oxygen demand, and permanganate index in the highly urbanized Guanlan River Basin were significantly higher than those of the less urbanized Pingshan River Basin (P<0.05). Redundancy analysis based on the Bray-Curtis distance showed that the proportion of urban land and total nitrogen were the main factors affected the difference of fish communities in the Guanlan and Pingshan River Basins. Changes of river habitat from urbanization reduced biodiversity of the native fishes. Thus, restoring native fish biodiversity in river ecological management and protection is the important direction of aquatic objective-based management. 参考文献 相似文献 引证文献

Understanding the Temporal Dynamics of a Lowland River Fish Community at a Hazardous Intake and Floodgate to Inform Safe Operation

Understanding the Temporal Dynamics of a Lowland River Fish Community at a Hazardous Intake and Floodgate to Inform Safe Operation

Monitoring fish communities through environmental DNA metabarcoding in the fish pass system of the second largest hydropower plant in the world

The Itaipu Hydroelectric Power Plant is the second largest in the world in power generation. The artificial barrier created by its dam imposes an obstacle for fish migration. Thus, in 2002, a fish pass system, named Piracema Channel, was built to allow fish to access areas upstream of the reservoir. We tested the potential of environmental DNA metabarcoding to monitor the impact of both the dam and associated fish pass system in the Paraná River fish communities and to compare it with traditional monitoring methods. Using a fragment of the 12S gene, we characterized richness and community composition based on amplicon sequence variants, operational taxonomic units, and zero-radius OTUs. We combined GenBank and in-house data for taxonomic assignment. We found that different bioinformatics approaches showed similar results. Also, we found a decrease in fish diversity from 2019 to 2020 probably due to the recent extreme drought experienced in southeastern Brazil. The highest alpha diversity was recorded in the mouth of the fish pass system, located in a protected valley with the highest environmental heterogeneity. Despite the clear indication that the reference databases need to be continuously improved, our results demonstrate the analytical efficiency of the metabarcoding to monitor fish species.

Climate Change Effects on Fish Passability across a Rock Weir in a Mediterranean River

Climate change represents a major challenge for the management of native fish communities in Mediterranean rivers, as reductions in discharge may lead to a decrease in passability through small barriers such as weirs, both in temporary and perennial rivers. Through hydraulic modelling, we investigated how discharges from a large hydropower plant in the Tagus River are expected to affect the passability of native freshwater fish species through a rock weir (Pego, Portugal), equipped with a nature-like fish ramp. We considered not only mean daily discharge values retrieved from nearby gauging stations (1991–2005) for our flow datasets, but also predicted discharge values based on climatic projections (RCP) until the end of the century (2071–2100) for the Tagus River. Results showed that a minimum flow of 3 m3 s−1 may be required to ensure the passability of all species through the ramp and that passability was significantly lower in the RCP scenarios than in the historical scenario. This study suggests that climate change may reduce the passability of native fish species in weirs, meaning that the construction of small barriers in rivers should consider the decreases in discharge predicted from global change scenarios for the suitable management of fish populations.

Multiple anthropogenic pressures in Eastern Mediterranean rivers: Insights from fish-based bioassessment in Greece

Surveys of anthropogenic pressures and their effect on river fish communities have rarely been conducted in the eastern Mediterranean countries, in contrast to the rest of Europe. An electrofishing dataset of 1586 samples (818 sites) was analyzed to investigate human-induced pressures on river fish assemblages in Greece. Pressure patterns and pressure-impact analysis towards the national fish bioassessment index (HeFI) and its four constituent metrics are depicted. At each sampling site 11 anthropogenic pressure variables were assessed, and several integrated/grouped pressure indices were computed, including hydrology, morphology, connectivity, and water quality. Almost 60% of samples were classified as impacted. The most common pressure groups affecting Greek rivers were hydrology recorded at 714 (45%) samples, morphology at 692 (44%) and artificial barriers at 382 (24%) samples. A similar pattern persists among the six investigated freshwater ecoregions in Greece. The most impacted ecoregions were Thrace (76% impacted samples), Western Aegean (67% impacted samples) and Macedonia-Thessaly (67% impacted samples). Lowlands and large rivers displayed higher levels of degradation, but water pollution was not recognized as a key stressor in most running waters. Pressure-impact analysis demonstrates that all HeFI component metrics (insectivorous, omnivorous, benthivores, potamodromous species) respond as expected to almost all integrated pressure indices considered, as regards: a) the direction of response, and b) the response to pressure intensity gradients. However, the longitudinal connectivity stressor clearly fails to respond towards metrics. The findings confirm the usefulness of model-based indices, using fish assemblage functional metrics as bioassessment tools. Specific recommendations for refining the tools are provided.

Environmental DNA metabarcoding as a tool for biodiversity assessment and monitoring: reconstructing established fish communities of north‐temperate lakes and rivers

AbstractAimTo evaluate the ability of precipitation‐based environmental DNA (eDNA) sample collection and mitochondrial 12S metabarcoding sequencing to reconstruct well‐studied fish communities in lakes and rivers. Specific objectives were to 1) determine correlations between eDNA species detections and known community composition based on conventional field sampling, 2) compare efficiency of eDNA to detect fish biodiversity among systems with variable morphologies and trophic states, and 3) determine if species habitat preferences predict eDNA detection.LocationUpper Great Lakes Region, North America.MethodsFish community composition was estimated for seven lakes and two Mississippi River navigation pools using sequence data from the mitochondrial 12S gene amplified from 10 to 50 water samples per waterbody collected in 50‐mL centrifuge tubes at a single time point. Environmental DNA (eDNA) was concentrated without filtration by centrifuging samples to reduce per‐sample handling time. Taxonomic detections from eDNA were compared to established community monitoring databases containing up to 40 years of sampling and a detailed habitat/substrate preference matrix to identify patterns of bias.ResultsMitochondrial 12S gene metabarcoding detected 15%–47% of the known species at each waterbody and 30%–76% of known genera. Non‐metric multidimensional scaling (NMDS) assessment of the community structure indicated that eDNA‐detected communities grouped in a similar pattern as known communities. Discriminant analysis of principal components indicated that there was a high degree of overlap in habitat/substrate preference of eDNA‐detected and eDNA‐undetected species suggesting limited habitat bias for eDNA sampling.Main conclusionsLarge numbers of small volume samples sequenced at the mitochondrial 12S gene can describe the coarse community structure of freshwater systems. However, additional conventional sampling and environmental DNA sampling may be necessary for a complete diversity census.

Estimation of biodiversity metrics by environmental DNA metabarcoding compared with visual and capture surveys of river fish communities

Abstract Information on α‐ (local), β‐ (between habitats), and γ‐ (regional) diversity is fundamental to understanding biodiversity as well as the function and stability of community dynamics. Methods like environmental DNA (eDNA) metabarcoding are currently considered useful to investigate biodiversity. We compared the performance of eDNA metabarcoding with visual and capture surveys for estimating α‐ and γ‐diversity of river fish communities, and nestedness and turnover in particular. In five rivers across west Japan, by comparison to visual/capture surveys, eDNA metabarcoding detected more species in the study sites (i.e. α‐diversity). Consequently, the overall number of species in the region (i.e. γ‐diversity) was higher. In particular, the species found by visual/capture surveys were encompassed by those detected by eDNA metabarcoding. Estimates of community diversity within rivers differed between survey methods. Although we found that the methods show similar levels of community nestedness and turnover within the rivers, visual/capture surveys showed more distinct community differences from upstream to downstream. Our results suggest that eDNA metabarcoding may be a suitable method for community assemblage analysis, especially for understanding regional community patterns, for fish monitoring in rivers.

Fish assemblages of the St. Joseph River Watershed, Indiana: Effects of mainstem dams

AbstractWe tested for effects of two dams on fish assemblages in the St. Joseph River, Indiana. Fishes were collected by boat electrofisher twice annually, at 23 sites from 1998 to 2018. Fish collection data were aggregated into CPUE counts of species per 500 m, and CPUE were pooled across sites above and below the dams. We used multivariate analyses to test for spatial and temporal variation for assemblages above and below dams. Assemblages above and downstream of the dams differed significantly when examined by collection year. The effects (abundances of fish species) of the dams on fish assemblages were different at the South Bend dam from those at the Elkhart dam. Trajectories of temporal change in fish assemblages above and below dams were all gradual and directional. Temporal variation in fish abundance categorised into trophic traits (guilds) differed by location. We suggest that moderate to high stress from anthropogenic impacts on the St. Joseph River appears to result in high assemblage variation above and below dams. The St. Joseph River fish community appears to be unstable, likely from multiple anthropogenic impacts to water quality, habitat degradation and hydrologic alteration. We found that 25 of 33 hydrologic variables in four of five Indicators of Hydrological Alteration groups were significantly altered from 1931 to 2019. However, hydrology variation as potential disturbance events did not visually match observed temporal assemblage variation.

Bluegill Habitat Use in the Upper Mississippi River

Anthropogenic modifications to the environment have had damaging effects on the wildlife that depend on those natural ecosystems. Specific to Upper Mississippi River fishes, channelization, dams, and loss of floodplain connectivity have all been purported as deleterious. In the face of these habitat modifications, understanding habitat requirements of native species is needed to help guide management and restoration efforts. Furthermore, bluegill (Lepomis macrochirus) are an important indicator species that may provide insight to habitat needs of the broader fish community (e.g., “canary in a coal mine”). Prior research suggests bluegill require a mosaic of habitats throughout all life stages (e.g., main channel to backwater connection). As such, the objective of this study was to identify the habitat needs of bluegill in the Upper Mississippi River. We evaluated bluegill habitat use via electrofishing conducted by the U.S. Army Corps of Engineers’ Long-Term Resource Monitoring (LTRM) element. Electrofishing events (n = 4868) were conducted at three field sites throughout the Upper Mississippi River from 1993 to 2017. Our analysis of catch data (n = 83,352) indicates that bluegill prefer backwater macrohabitat over main channel and side channel habitats. Bluegill abundance varied between microhabitat characteristics. Bluegill catch rates were highest in low-flow areas, with velocities ranging from 0 to 0.09 m/sec. In general, catch rates were highest across all pools in moderately shallow depths (0–1.5 m) and in silty substrates. Management efforts that focus on the preservation of backwater habitat and connectivity to the main channel should help to sustain bluegill populations in the Upper Mississippi River. The information garnered in this study can be used to help direct management efforts that not only favor bluegill, but also other members of the Upper Mississippi River fish community.

Impact of Chaitén Volcano ashfall on native and exotic fish recovery, recolonization, and abundance

The effects of volcanic disturbance on aquatic communities and their recovery are poorly studied. To fill this gap, we explored the effects on fish communities in rivers in Argentina of the 2008 eruption of Chaitén Volcano in southern Chile (42.8° lat. S). The eruption produced volcanic plumes of ash that persisted in the atmosphere for several months. Borne on westerly winds, deposits of tephra crossed the Andes Mountains, reaching the Atlantic coast (Argentina). We compared the pre- and post-eruption abundances of a native catfish Hatcheria macraei, and two introduced trout from rivers covered by the volcanic plumes (Argentina) using Before-After-Control-Impact analysis to explore fish recovery. Total suspended solids from volcanic ashfall, macroinvertebrate abundance and richness, and species ecological attributes influenced the spatial arrangement of fish in rivers. Twenty-one months after the eruption, Rainbow Trout, Oncorhynchus mykiss, had not returned to pre-eruption abundances in the sampled rivers, and only four rivers had regained pre-eruption species composition, suggesting that disturbance is still ongoing. The abundance of introduced fishes was strongly, negatively correlated with TSS, suggesting that ashfall affected these fish probably by clogging and abrasion of the gills. Fish recolonized previously occupied habitats 4 days to 9 months after the disturbance. Hatcheria macraei was the slowest to recolonize, whereas O. mykiss were the pioneer fish in 4 rivers following the eruption and recolonized all 5 rivers where they were present prior to the eruption. In one river, the catfish and the Brown Trout, Salmo trutta, were still absent 21 months post-eruption, potentially owing to the lack of riparian cover that would have deflected the entry of ash. Rainbow Trout suffered significant declines in abundance, whereas Brown Trout and catfish generally did not, owing to their ecological attributes. Total fish abundance was negatively correlated with ash thickness, but positively related to prey availability.

Spring flow lost: a historical and contemporary perspective of an urban fish community

Water quality and quantity within the upper San Antonio River (Bexar County, Texas) were supported historically from spring flows of the Edwards Aquifer. Since the 1700s, water quality, quantity, physical aquatic habitats, and presumably fish communities have been altered in the upper San Antonio River, including loss of spring flow and replacement of base flow by treated wastewater. The upper San Antonio river fish community provides a unique opportunity to fill a gap in knowledge on spring-associated fish responses to spring flow loss. The purpose of our study was to describe temporal changes in the upper San Antonio River fish community in relation to increased anthropogenic alterations from reported fish collections and infer from reference conditions. Comparisons with reference conditions were necessary since anthropogenic alterations occurred before the first fish collections within the basin. We found the upper San Antonio River fish community changed through time with increases in native and introduced fishes and decreases in spring-associated fish richness and relative abundances. Decreases in spring-associated fish richness and relative abundances were attributed to decreases in spring flow and to changes in water quality; however, specific mechanisms between loss of spring flow and spring-associated fishes are unknown at this time. Quantifying historical fish community changes through time in systems with a long history of urbanization is difficult, but our assessment provides a greater understanding of how spring flow loss due to increasing water demand in highly urbanized areas can alter communities with spring-associated species.

Multiple stressor effects on alpha, beta and zeta diversity of riverine fish

We examined the effects of regional scale land use and local scale environmental and biotic stressors on alpha, beta and zeta diversities of native fish communities in wadeable streams and non-wadeable rivers in the Danube basin, Hungary. Relationships among land use and local scale environmental and biotic stressors were weak both in streams and rivers, suggesting that these stressors act relatively independently. Alpha diversity decreased strongly with increasing local scale environmental stressor intensity in rivers. On the contrary, its response to stressors was more obscure in streams, where the best-fit statistical model indicated the importance of the interaction between land use, local scale environmental and biotic stressors, while the secondly ranked model highlighted the negative impact of local scale environmental stressors. Analysis of variance using distance matrices provided evidence that stressors alone and in interactions explained compositional differences of pairs of study sites (beta diversity). Considering the degree of overall degradation, both local (alpha) and among-site (beta and zeta) diversity indices responded to increasing stressor intensity, generally negatively. Riverine fish communities showed higher degrees of similarity (lower beta and higher zeta) than stream fish communities. They also showed increasing similarity (i.e. homogenization) with increasing overall stressor intensity, unlike stream fish communities, which showed no relationship with overall stressor intensity. Our results suggest that the relationships between land use and local scale environmental and biotic stressors can be complex and so do their effects on biodiversity. While stressor specific indices can provide information on the role of specific stressors in some cases, the examination of overall stressor effects is needed to assess realistically the effects of anthropogenic disturbances on native fish diversity. Diversity indices that quantify among-site changes in species composition, such as measures of beta and zeta diversity, can be fruitful for better understanding the role of multiple stressors in structuring ecological communities.

Monitoring freshwater fish communities in large rivers using environmental DNA metabarcoding and a long-term electrofishing survey.

Monitoring freshwater fish communities in a large human-impacted river is a challenging task. The structure of fish assemblages has been monitored yearly in the Marne and the Seine Rivers, across the Paris conurbation, France, using traditional electrofishing (EF) surveys since 1990, in accordance with the European Water Framework Directive. In addition, metabarcoding of DNA extracted from environmental samples (eDNA) was concomitantly conducted in nine sampling sites in 2017 and in 2018 to compare the estimates of species richness and relative abundance among three methods: annual, long-term EF monitoring and eDNA. The present study confirms better detection of fish species using eDNA compared to annual EF. eDNA metabarcoding was also more efficient for species detection than a 3-6-year EF survey but was similar or less efficient than a long-term EF survey of 14 years of monitoring. In addition, the numbers of reads per species relative to the total number of reads significantly increased with (a) increasing relative abundance (relative percentage of individuals caught per species) and (b) increasing number of years that a fish species was detected during the 2000-2018 period. These results suggest that eDNA could reflect local population persistence.

Fish out of water: Aquatic parasites in a drying world.

Although freshwater ecosystems are among the most diverse and endangered in the world, little attention has been paid to either the importance of parasitic disease as a threatening process for freshwater organisms, or the co-extinction risk of freshwater parasites. In this review, we use theoretical and empirical studies of host/parasite interactions to examine these issues, particularly with respect to the threat posed by climate change to fish and parasite communities in intermittent rivers. Intermittent rivers are those that cease to flow at any point in time or space, with isolated pools providing ecological refuges for freshwater biota between streamflow events. Intermittent rivers are the dominant river type in arid, semi-arid and Mediterranean regions; areas of the world that have experienced dramatic decreases in streamflow as a result of climate change. Reduced streamflow decreases the number, size and connectivity of refuge pools in intermittent rivers, with important consequences for free-living aquatic organisms, particularly fishes, and their parasitic fauna. As a result of more frequent and sustained periods of no flow, parasite diversity within refuge pools is expected to decrease, with a concomitant increase in the prevalence and intensity of those parasite species which do survive, particularly host generalists. Decreased connectivity between refuge pool communities should increase the spatial modularity of host/parasite interactions, leading to a greater structuring of host and parasite communities along the river. This increases the probability of species loss (for both hosts and their parasites), as local extinctions cannot be reversed by colonisation from other localities.

A diagnosis-based approach to assess specific risks of river degradation in a multiple pressure context: Insights from fish communities

In the context of increasing pressure on water bodies, many fish-based indices have been developed to evaluate the ecological status of rivers. However, most of these indices suffer from several limitations, which hamper the capacity of water managers to select the most appropriate measures of restoration. Those limitations include: (i) being dependent on reference conditions, (ii) not satisfactorily handling complex and non-linear biological responses to pressure gradients, and (iii) being unable to identify specific risks of stream degradation in a multi-pressure context. To tackle those issues, we developed a diagnosis-based approach using Random Forest models to predict the impairment probabilities of river fish communities by 28 pressure categories (chemical, hydromorphological and biological). In addition, the database includes the abundances of 72 fish species collected from 1527 sites in France, sampled between 2005 and 2015; and fish taxonomic and biological information. Twenty random forest models provided at least good performances when evaluating impairment probabilities of fish communities by those pressures. The best performing models indicated that fish communities were impacted, on average, by 7.34 ± 0.03 abiotic pressure categories (mean ± SE), and that hydromorphological alterations (5.27 ± 0.02) were more often detected than chemical ones (2.06 ± 0.02). These models showed that alterations in longitudinal continuity, and contaminations by Polycyclic Aromatic Hydrocarbons were respectively the most frequent hydromorphological and chemical pressure categories in French rivers. This approach has also efficiently detected the functional impact of invasive alien species. Identifying and ranking the impacts of multiple anthropogenic pressures that trigger functional shifts in river biological communities is essential for managers to prioritize actions and to implement appropriate restoration programmes. Actually implemented in an R package, this approach has the capacity to detect a variety of impairments, resulting in an efficient assessment of ecological risks across various spatial and temporal scales.

Diel patterns in spatial distribution of fish assemblages in lentic and lotic habitat in a regulated river

AbstractFish assemblages in large rivers are governed by spatio‐temporal changes in habitat conditions, which must be accounted for when designing effective monitoring programmes. Using boat electrofishing surveys, this study contrasts species richness, catch per unit effort (CPUE), total biomass, and spatial distribution of fish species in the Saint John River, New Brunswick, Canada, sampled during different diel periods (day and night) and macrohabitats (hydropower regulated river and its reservoir) in the vicinity of the Mactaquac (hydropower) Generating Station. Taxa richness, total CPUE, and total biomass were significantly higher during night surveys, resulting in marked differences in community composition between the two diel periods. Furthermore, the magnitude of diel differences in catch rate was more pronounced in lentic than in lotic macrohabitats. The required sampling effort (i.e., number of sites) to increase accuracy and precision of CPUE estimates varied widely between fish species, diel periods, and macrohabitats and ranged from 15 to 185 electrofishing sites. Determining a correction factor to contrast accuracy and precision of day‐ with night‐time surveys provide useful insights to improve the design of long‐term monitoring programmes for fish communities in large rivers. The study also shows the importance of multihabitat surveys to detect differences in the magnitude of diel changes in fish community metrics.

Influence of a high‐head dam as a dispersal barrier to fish community structure of the Upper Mississippi River

AbstractIn river systems, high‐head dams may increase the distance‐decay of fish community similarity by creating nearly impermeable dispersal barriers to certain species from upstream reaches. Substantial evidence suggests that migratory species are impacted by dams, and most previous studies in stream/river networks have focused on small streams and headwaters. Here, we assess whether a high‐head dam (Lock and Dam 19; LD 19) on a large river, the Upper Mississippi River (UMR), substantially alters fish community structure relative to variability expected to occur independent of the dam's effect as a fish dispersal barrier. Using fish catch per unit effort data, we modelled the distance‐decay function for the UMR fish community and then estimated the similarity that would be expected to occur across LD19 and compared it with measured similarity. Measured similarity in the fish community above and below LD19 was close to the expected value based on the distance‐decay function, suggesting LD19 does not create an abrupt transition in the fish community. Although some migratory fish species no longer occur above LD19 (e.g., skipjack herring, Alosa chrysochloris), these species do not occur in high abundance below the dam and so do not drive variation in fish community structure. Instead, much of the variation in species structure is driven by the loss/gain of species across the latitudinal gradient. Lock and Dam 19 does not appear to be a clear transition point in the river's fish community, although it may function as a meaningful barrier for particular species (e.g., invasive species) and warrant future attention from a management perspective.

Individual differences exceed species differences in the movements of a river fish community

AbstractRepeatable individual differences often account for large proportions of intraspecific variation in animal movements. However, meta-population models have continued to rely on single species-level and season-specific species-level means for movement prediction. Here, we test the hypothesis that repeatable individual differences can account for a similar proportion of movement distance variation as species differences. We used radio telemetry to generate repeated measures of movement from 504 hetero-specific fish. We tracked 5 large bodied fish species (Salvelinus confluentus, Oncorhynchus mykiss, Prosopium williamsoni, Thymallus arcticus, and Sander vitreus) in the upper reaches of the Peace River, British Columbia, Canada, over 8 years. We applied a hierarchical framework to partition repeatability of movement distances at the intra- and interspecific biological levels, and among short-term (within-season) and long-term (across seasons and years) temporal levels. Our results show that long-term movement distance repeatability was higher at the intraspecific level than at the interspecific level, demonstrating that animal personality can account for more variation in movement than species differences. These findings provide a novel, community level demonstration of the importance of individual variation, highlighting the predictive gains associated with a shift in the focus of spatial ecology, away from species mean and seasonal species-level mean predictive approaches, towards a spatial behavioral types-based predictive approach.

Integrating Meso-Scale Habitat Modelling in the Multicriteria Analysis (MCA) Process for the Assessment of Hydropower Sustainability

The increasing number of water abstractions and water-use conflicts in alpine regions represents a significant threat for these fragile aquatic ecosystems. The use of tools, like multicriteria analysis (MCA), can support related decision-making processes towards sustainable solutions. In this paper, an innovative approach to assess water withdrawals sustainability by integrating the MesoHABSIM (Mesohabitat Simulation Model) into an MCA framework is presented and discussed. The methodology was implemented by replacing, within the MCA assessment, Water Framework Directive biological indicators with the MesoHABSIM based river Habitat Integrity Index, related to watercourse discharge and morphology, which allows quantifying the impacts of withdrawals on river ecosystems and fish communities. The resulting MCA procedure considers four criteria (energy, environment and fishing, landscape, economy) and requires only the use of measurable indicators based on watercourse discharge and its continuous monitoring. It was tested in Aosta Valley region (NW Italy) to both ex ante and ex post scenarios, for different types of water withdrawals and, currently, 20 experimentations, involving 58 hydropower plants and 12 farmer consortia, are ongoing. The proposed MCA process demonstrated its applicability with an increased decision-making quality and involved stakeholders’ satisfaction and is being officially endorsed in the regional River Strategic Plan.