Migratory Fish Research Articles

A typology of potential hydraulic barriers to adult salmon migration in a bedrock river

Adult Pacific salmon (Oncorhynchus spp.) in the Fraser River, British Columbia, can die trying to retrace and ascend the river network to their natal spawning grounds due to hydraulic barriers, where encounter velocities exceed swim speeds of adult salmon. We evaluated river hydraulics, river morphology, and swimming ability to better understand these potential hydraulic barriers. A 375 km centerline velocity survey of the Fraser Canyon identified 22 high velocity locations where the distribution of velocity within the reach could produce a hydraulic barrier. We identified and studied three flow types associated with these 22 high velocity locations: 1) plunging flows, 2) rapids, and 3) overfalls, using drone footage at various discharges to examine flow structure and compare surface velocities with swimming modes. Complex flow within the major hydraulic features highlight the spatial locations requiring anaerobic swimming and areas of potential recovery that change with discharge. This approach can be used to improve the understanding of fish migration limits in a natural river system and aid in future mitigation.

Emerging pollutants: Risks in salmon fish migration. A review

The release of pollutants into the environment is a serious ecological problem due to the significant risks they pose both to ecosystems and to human health. The review considers the issues of detection and distribution of new pollutants, as well as sources of their entry into the environment and potential impact on ecosystems. The problem of wastewater pollution is especially urgent in the context of conservation of salmonid fish species. Pharmaceutical and veterinary drugs, components of personal hygiene products, microplastics, per- and polyfluorinated substances, brominated flame retardants, oil and a number of other toxicants enter freshwater bodies, which are especially important for the early stages of the salmon development and its following migration. The presence of pollutants in the aquatic environment depends on a source, their ability to bioaccumulate, as well as to degrade in the processes of biological and abiotic purification. High-resolution mass spectrometry in combination with gas or liquid chromatography can be recommended for detection of new pollutants. Due to high mass measurement accuracy and high specificity, this method is able to effectively identify pollutants even in the complex fish matrix. When conducting non-targeted and targeted screening with highly sensitive full scanning, it is advisable to use high-resolution mass analyzers (TOF, Q-TOF, Q-Orbitrap), which allow determining a number of new compounds. A promising direction in the complex assessment of the impact of pollutants on salmon fish species and the identification of indicators characterizing this impact is metabolomics. It is based on the study of low-molecular organic compounds — metabolites, both intermediate and final metabolic products in body fluids and tissues. Metabolomic profiling allows identifying important markers of the state of a water body under the influence of pollutants, which is necessary for the development of comprehensive regulations and guidelines for the effective handling of these pollutants.

Seasonally flooded landscape connectivity and implications for fish in the Napo Moist Forest: A high-resolution mapping approach

The Amazon River Basin's fish diversity is shaped by its dynamic flood-pulse system, critical for hydrological and ecological connectivity. This study examines the Napo Moist Forest (NMF) ecoregion, mapping permanent and seasonally flooded areas from 2018 to 2021 using remote sensing and deep learning models. We aimed to map these areas at a high spatial resolution (10-m pixels) and analyse their role in maintaining lateral connectivity essential for fish diversity. Using synthetic aperture radar data from Sentinel-1 combined with deep learning algorithms, we produced high-accuracy flood maps to assess landscape connectivity between rivers and floodplains. Our methodology included creating a ground truth dataset with the Normalized Difference Water Index and integrating high-resolution optical data for model training, overcoming challenges of cloud coverage and dense vegetation. Our predictive model achieved high accuracy (mean pixel accuracy = 97 %) and consistently predicted 4801 km² of surface water, with only 3 % (130 km²) being seasonally flooded areas over four years. The Caquetá, Bajo Marañón, Napo, and Pastaza watersheds accounted for nearly 60 % of the flooded areas, highlighting their ecological importance. Connectivity analysis in three areas of interest within the NMF ecoregion revealed important seasonal and interannual fluctuations in hydrological connectivity due to changes in flooded patch characteristics. Reductions in the number and flooded patch area during low water seasons increased the distance between patches, leading to a disconnection between flooded areas, channels and rivers. Despite hydrological fluctuations, certain patches maintained consistent flooding, critical for lateral connectivity and sustaining aquatic biodiversity. These seasonally flooded areas act as connectors, influencing patch dynamics and connectivity with tributaries. Seasonal and interannual variations in hydrological connectivity are crucial for sustaining fish diversity. Conserving dynamic floodplains supports migratory fish life cycles and biodiversity. This study underscores the importance of high-resolution temporal and spatial data in conservation planning for aquatic ecosystems.

Examining Bald Eagle Contaminant Exposure and Reproductive Risk Above and Below Dams on Great Lakes Tributaries.

Removing lowermost dams can reestablish fish passage on Great Lakes tributaries. This can increase the transfer of contaminants from anadromous fish to piscivorous wildlife upstream; however, concentrations of bioaccumulative contaminants in Great Lakes fish have decreased over the last several decades. We analyzed concentrations of PCBs and the toxic equivalence (TEQs) calculated from PCBs, DDTs, other organochlorine pesticides, and PBDEs in the plasma of bald eagle nestlings above and below lowermost dams on five river systems in Michigan from 1999 to 2013. We examined relationships between contaminants and metrics of reproductive success from 1997 to 2018, including the effects of year and location relative to the lowermost dam. Σ20PCB and p,p'-DDE were important in characterizing differences in contaminant mixtures above and below dams. Concentrations of contaminants were generally greater below dams than above. There were generally greater nest success and more nestlings per nest below dams, but nest location explained little variability (R2 values = 0.03-0.15). Neither Σ20PCB nor p,p'-DDE was a significant predictor of 5-year productivity means by river reach despite concentrations exceeding previously established effects thresholds for healthy bald eagle populations in the Great Lakes (≥ 1 nestling/nest). Our study indicates that dams may continue to reduce the upstream movement of contaminants to bald eagles, but at the measured concentrations, contaminants did not impair productivity and reproductive success as indicated by nestlings per nest. Additional information about population dynamics could clarify population-level effects of contaminants on bald eagles and to what degree these populations are self-sustaining throughout the Great Lakes.

Ruin-of-the-rivers? A global review of run-of-the-river dams.

The classification of a hydropower scheme as run-of-the-river (or run-of-river; ROR) evokes an image of a low-impact installation; however, examination of eight case studies worldwide shows that substantial negative societal and ecological impacts are tied to them, albeit in somewhat different ways. We conclude that ROR dams not only potentially displace communities, disrupt livelihoods, and degrade environments in surrounding areas, but they also divert water from areas of need, impact aquatic ecology through habitat destruction and disruption of fish migrations, emit non-trivial amounts of greenhouse gases over the lifespan of the project, and disrupt streamflow in downstream river sections. While these negative impacts vary on a case-by-case basis, medium and large ROR dams consistently have multiple and cumulative impacts, even when not having appreciable reservoirs. We contend that many impactful dams do not qualify as low-impact ROR projects, despite being defined as such. Such mislabeling is facilitated in part by the ambiguous definition of the term, which risks the ROR concept being used by proponents of impactful structures to downplay their negative effects and thus mislead the public or gain status, including within the Clean Development Mechanism in relation to mitigating climate change.

New evidence of alternative migration patterns for two Mediterranean potamodromous species

Iberian barbel (Luciobarbus bocagei Steindachner, 1864) and Iberian nase (Pseudochondrostoma polylepis Steindachner, 1864) are two Mediterranean potamodromous fish species known to perform annual upstream migrations to reach spring spawning grounds. In the Mondego River basin, at the Coimbra dam, migratory movement patterns and individual size structure were assessed through a video recording monitoring system installed on an upstream section of a vertical-slot fish pass. Visual census for these target species during two consecutive annual cycles (2013–2014) revealed alternative migratory patterns, with the first peak of upstream movements in autumn, for both barbel (October–November) and nase (November–December). Circadian movements of both species showed a diurnal preference, contrary to what is usually described for these species. Size structure analysis for individuals of both species showed significant intra-annual differences in the size of migrating fish. Boosted regression trees models applied to the 2013–2014 visual count data identified flow and temperature as the most influential environmental predictors, triggering both species’ movements in each direction in the study years. These results provide novel information on the timing of the migratory movements of these potamodromous fish, which can be used to adapt current management and conservation measures to the specificities of their migratory behaviour.

Short-Term Effects of Abrupt Salinity Changes on Aquaculture Biofilter Performance and Microbial Communities

In recirculating aquaculture systems (RASs), ammonia excreted by fish must be converted to the less toxic nitrate before recirculation. Nitrifying microorganisms in biofilters used for this transformation can be sensitive to changes in salinity, which can present issues for systems that raise anadromous fish such as Atlantic salmon. Freshwater biofilters maintained at a low level of salinity (such as biofilters operated in coastal areas) may be better equipped to handle more drastic salinity shifts; therefore, experiments were performed on freshwater and low-salinity (3 ppt) biofilters to assess their ability to recover nitrification activity after an abrupt change in salinity (3, 20, and 33 ppt). Two-week tests showed full nitrification recovery in freshwater biofilters after a shift to 3 ppt but no ammonia oxidation in 20 or 33 ppt. Low-salinity-adapted filters (transitioned from 0 to 3 ppt) showed a small recovery (about 11%) after a shift to 20 ppt, and no activity when shifted to 33 ppt. Illumina sequencing revealed that, while nitrification was slowed or stopped with shifting salinities, the nitrifiers survived the salinity increases; conversely, the heterotrophic communities were more greatly affected and were reduced in proportion with increasing salinity. This work indicates that biofilters operated at low salinity may recover more quickly after large salinity changes, though this slight benefit may not outweigh the cost of low-level salinity maintenance. Further research into halotolerant heterotrophs in biofilms may increase the effectiveness of nitrifying biofilters under variable salinities.

Determining the Fish Migration Patterns Based on Fish Habitat Assessment at a River Confluence

ABSTRACTMuch effort has been devoted to predicting fish migration routes to assist target species migration, and yet, fish migration science and practice remain imperfect. This study aimed to predict the migration paths of Gymnocypris przewalskii at the river confluence in the Qinghai Lake basin. The authors proposed an approach for fish migration route prediction, which involves a hydrodynamic module, a habitat model and a fish migration module. The TELEMAC‐MASCARET system was used to simulate hydrodynamic conditions and statistical analyses were carried out. During the flood season, G. przewalskii migrates downstream, whereas during the migratory season, they migrate upstream. The results indicate that flow velocity was the most significant hydrodynamic parameter affecting fish migration behaviour. The optimal flow velocity range for the target fish species was between 0.7 and 1.7 m/s. The impact of water depth was only observed in low discharge situations. Besides, the temperature plays a vital role in determining fish migration and abundance. However, the results reveal that in the morning hours, the temperature exhibits a range of 10°C to 16°C, and in the noon, the average temperature ranges from 16°C to 19°C, with a maximum temperature reaching 23°C. These temperature variations enable fish to migrate towards the tributary offering a more favourable water temperature during route selection at a river confluence. The study concludes that future research should consider incorporating the swimming capacity of the focal fish species to provide insights into fish migration patterns.

The Global Dam Watch database of river barrier and reservoir information for large-scale applications.

There are millions of river barriers worldwide, ranging from wooden locks to concrete dams, many of which form associated impoundments to store water in small ponds or large reservoirs. Besides their benefits, there is growing recognition of important environmental and social trade-offs related to these artificial structures. However, global datasets describing their characteristics and geographical distribution are often biased towards particular regions or specific applications, such as hydropower dams affecting fish migration, and are thus not globally consistent. Here, we present a new river barrier and reservoir database developed by the Global Dam Watch (GDW) consortium that integrates, harmonizes, and augments existing global datasets to support large-scale analyses. Data curation involved extensive quality control processes to create a single, globally consistent data repository of instream barriers and reservoirs that are co-registered to a digital river network. Version 1.0 of the GDW database contains 41,145 barrier locations and 35,295 associated reservoir polygons representing a cumulative storage capacity of 7,420 km3 and an artificial terrestrial surface water area of 304,600 km2.

European eel (Anguilla anguilla) survival modeling based on a 22-year capture-mark-recapture survey of a Mediterranean subpopulation.

Since the 1980s, the European eel (Anguilla anguilla) has declined by over 90% in recruitment across its European and North African distribution area. This diadromous fish spawns at sea and migrates into continental waters, where it grows for three to more than 30 years, depending on habitat conditions and location. During their growth, different habitat use tactics can locally influence the life-history traits of eels, including their survival rates. Thus, the spatio-temporal dimension of this species is crucial for management. Based on a rare Mediterranean long-term survey of more than 20 years (2001-2022) in an artificial drainage canal connected to a vast brackish lagoon (the Vaccarès lagoon), we aimed to study the dynamics of one subpopulation's life-history traits. We used Bayesian multistate capture-mark-recapture (CMR) models to assess the temporal variability in survival and abundance at both seasonal and inter-annual scales, considering life-stage structure. High survival rates and low detection probabilities were found for the undifferentiated and female yellow stages. In contrast, female silver eels exhibited lower survival rates and higher capture probabilities. Estimating detection probabilities and survival rates enabled accurate assessment of relative abundance across different life stages and time periods. Our findings indicated a substantial decrease in the abundance of undifferentiated and female yellow eels in the early 2000s, whereas the abundance of female silver eels remained consistently low yet stable throughout the study period. Considering the life stage seemed essential to study the dynamics of the eel during its continental growing period. The present results will provide key elements to propose and implement suitable sustainable environmental management strategies for eel conservation.

Estimation of tributary–mainstem migration of freshwater fishes by Sr isotope analysis of otoliths

AbstractThe study of fish movement patterns in freshwater ecosystems remains a major focus of contemporary research. Small freshwater fish are known to migrate between tributaries and mainstems at different stages of their life history, helping to avoid local extinctions and maintain genetic diversity. However, fitting small fish species with telemetry equipment is difficult, making it challenging to track their detailed migration history via conventional methods. We evaluated the suitability of otolith isotope analysis for verifying the migration histories of small fish species inhabiting small tributaries. In this study, we compared the 87Sr/86Sr values in stream water and the otoliths of two fish species (Nipponocypris temminckii and Rhinogobius flumineus) inhabiting small streams. The 87Sr/86Sr ratios in the stream waters within the study area displayed considerable variation among tributaries. Our findings indicate that only N. temminckii has high dispersal ability, showing movement between tributaries or between tributaries and the mainstem in some locations. In contrast, such movement was not generally observed for R. flumineus. These results show the potential of 87Sr/86Sr as a tool for estimating the migration patterns of small fishes that inhabit small tributaries.

Anisakid nematode larvae in freshwater fishes in the St. Lawrence River (Québec, Canada)

Anisakid nematodes were observed in freshwater and anadromous fishes in the St. Lawrence River, Québec, Canada. Fish were caught at different locations across a 250 km gradient in the St. Lawrence ecosystem covering freshwater and estuarine habitats. Depending on the sampling sites, nematode prevalence ranged from 30% to 58% for sauger (Sander canadensis) and was 43% for Atlantic tomcod (Microgadus tomcod). For walleye (Sander vitreus), parasites were found only in a fluvial Lake (Lake Saint-Pierre) of the St. Lawrence River, with a prevalence of 23%. In all sampling sites, mean abundance of nematodes in the flesh was higher in sauger than in walleye. Presence of nematodes was significantly correlated with fish total length for walleye, sauger and Atlantic tomcod. Sealworm, Phocanema decipiens s.s., and whaleworm, Anisakis simplex s.s., were found and identified by molecular analysis in sauger and walleye in a fluvial lake (Lake Saint-Pierre), the fluvial estuary and the upper estuary of the St. Lawrence River, while Atlantic tomcod were found infected in a freshwater river tributary (Sainte-Anne River) during spawning.This is the first record of Ph. decipiens s.s. in a non-anadromous freshwater fish. The presence of sealworm and whaleworm in walleye and sauger is attributed to their forays into the brackish waters of the fluvial estuary and suggest large scale migrations between the brackish and the fresh waters of the St. Lawrence River.

Simple visualization of fish migration history based on high‐resolution otolith δ18O profiles and hydrodynamic models

AbstractOxygen‐stable isotope (δ18O) in otoliths has been useful to infer marine fish migrations. However, because otolith δ18O is affected by two parameters, temperature and δ18O of ambient water, its interpretation becomes challenging when neither of them is constant. Here, I describe a simple method using hydrodynamic models to visualize potential migration histories from high‐resolution otolith δ18O chronologies. By predicting the distribution of potential otolith δ18O, that is, otolith δ18O isoscape from modeled temperature and salinity distributions and comparing these with observed values, possible fish locations can be inferred. The demonstration of sardine juveniles in the western North Pacific region reproduced their seasonal northward migrations accurately. The predicted locations were consistent with the results of sampling surveys of eggs and juveniles and correctly approached the point where fish were caught. The methodological recommendations and the successful demonstration in this study may help in planning future sclerochronology research using carbonate δ18O values.

How SATURN is studying the impact of ship noise on the behaviour, health, energetics, and populations of aquatic organisms

The EU-funded SATURN project contributes to improve our understanding of the effects of ship noise on aquatic animals through several studies. Assessing the effects of underwater noise on aquatic animals is complex due to the diversity of taxa involved, each with their own sound sensitivity in terms of spectral and temporal aspects, as well as behavioural and physiological sensitivity to acoustic disturbances. To conduct exposure experiments on fish and invertebrates that are sensitive to the particle motion component of sound, we have developed innovative laboratory setups. Invertebrates are studied in an AQUAVIB exposure chamber, while migratory fish species are studied in a MIGRADOME swimming tunnel. The project also focuses on three marine mammal species: porpoises, pilot whales, and harbour seals. These species provide broad biological coverage of acoustic specialisations and relevant European habitats. Field data were collected using tags deployed on wild animals and dose-response relationships of marine mammal behaviour and energetics were established as a function of real-world exposure to ship noise. The effects on porpoise population are assessed using the updated DEPONS model. The results of SATURN will be transferred to stakeholders to inform management actions for the mitigation of the effects of acoustic pollution in marine habitats.

Passage efficiency through fishways of species of the family Cyprinidae and their management implications for fragmented rivers

The contemporary management of fragmented river systems is in a trade-off between the societal benefits of instream barriers (e.g. hydropower, flood risk management) and the ecological harms of their adverse impacts on fish populations. The consequent fragmentation can be mitigated through fishway construction, with mitigation performance measured using species-specific passage rates and efficiencies. There is, however, a bias in passage efficiency studies towards diadromous fishes and, although fish of the Cyprinidae family play a significant role in the fish assemblages of rivers worldwide, their passage efficiencies are poorly understood. Here, systematic review and meta-analyses assessed the passage efficiencies of cyprinid fishes through fishways that have been measured using telemetry methods. Passive integrated transponder (PIT) telemetry was the most common evaluation method of passage efficiency due to their high read rates and relatively low costs versus alternative telemetry methods. These methods revealed cyprinid passage efficiencies were highest through vertical slot fishways and lowest through nature-like constructions, with overall passage rates comparing favourably to anadromous salmonid fishes. Fish were most active during spring and summer, with passage and associated movements often related to spawning. Passage rates of non-native fishes were also higher than for native fishes. Despite the growing acknowledgment of how fishways influence potamodromous fish dispersal and distribution in rivers, passage data remain scarce, preventing managers and policy-makers from making informed decisions on optimal passage solutions for multiple fish species in highly fragmented rivers.

Evaluating intra- and inter-life stage density-dependent dynamics for management of perennial amphidromous fish.

Compensatory density-dependent (DD) processes play an integral role in fisheries management by underpinning fundamental population demographics. However, DD processes are often assessed only for specific life stages, likely resulting in misleading evaluations of population limitations. Here, we assessed the relative roles of intra- and inter-life stage DD interactions in shaping the population dynamics of perennial freshwater fish with demographically open populations. Specifically, we monitored populations of amphidromous banded kōkopu (Galaxias fasciatus), giant kōkopu (Galaxias argenteus), and shortjaw kōkopu (Galaxias postvectis) in five streams where migratory post-larvae are fished and in three no-take ("closed") streams located on New Zealand's South Island for two years. Using mark-recapture data, we investigated whether fishing altered densities of "small" (non-territorial recruits ≤1-year-old) and "large" (territorial fish >1-year-old) kōkopu size classes, and how subsequent density shifts affected the apparent survival and growth of each class while controlling for other confounding factors (e.g., habitat characteristics). We found that closed areas had substantially greater biomass of small kōkopu, particularly following the two-month fishing season. Despite this greater influx of recruits, there was no difference in the biomass of large kōkopu at the species level, or as a combined assemblage between stream types. This indicated that although fishing of post-larvae reduced recruit influxes into adult habitats, there was no subsequent evidence of recruitment-limitation within adult populations. Instead, kōkopu demographics were underpinned by intra- and inter-life stage DD competition and predation. Greater large fish densities played a key role in regulating the survival, growth, and/or presence of various kōkopu classes. In contrast, greater small fish densities had positive effects on the growth of opportunistic and insectivorous congeners, likely due to cannibalism and altered foraging behaviors, respectively. Our study details the prominent role of intra- and inter-life stage DD interactions in regulating the population dynamics of perennial migratory freshwater fishes, even in populations with inhibited recruit and juvenile availability. We emphasize the importance for fisheries management to implement recruitment dependencies and complex interactions between distinct life stages to avoid deleterious DD responses and ensure population persistence.

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.

Genetic Stock Identification Reveals Mismatches Between Management Areas and Population Genetic Structure in a Migratory Pelagic Fish.

Sustainable fisheries management is important for the continued harvest of the world's marine resources, especially as they are increasingly challenged by a range of climatic and anthropogenic factors. One of the pillars of sustainable fisheries management is the accurate identification of the biological units, i.e., populations. Here, we developed and implemented a genetic baseline for Atlantic herring harvested in the Norwegian offshore fisheries to investigate the validity of the current management boundaries. This was achieved by genotyping > 15,000 herring from the northern European seas, including samples of all the known populations in the region, with a panel of population-informative SNPs mined from existing genomic resources. The final genetic baseline consisted of ~1000 herring from 12 genetically distinct populations. We thereafter used the baseline to investigate mixed catches from the North and Norwegian Seas, revealing that each management area consisted of multiple populations, as previously suspected. However, substantial numbers (up to 50% or more within a sample) of herring were found outside of their expected management areas, e.g., North Sea autumn-spawning herring north of 62° N (average = 19.2%), Norwegian spring-spawning herring south of 62° N (average = 13.5%), and western Baltic spring-spawning herring outside their assumed distribution area in the North Sea (average = 20.0%). Based upon these extensive observations, we conclude that the assessment and management areas currently in place for herring in this region need adjustments to reflect the populations present. Furthermore, we suggest that for migratory species, such as herring, a paradigm shift from using static geographic stock boundaries towards spatial dynamic boundaries is needed to meet the requirements of future sustainable management regimes.

Fish Diversity of East Sea Streams in Nakdong River Region

Fish surveys were conducted near artificial structures installed in eight streams flowing from the Nakdong River region to the east coast of Korea. As a result of the survey, a total of 20,000 individuals belonging to nine orders, 17 families, and 47 species were found. The dominant species was Zacco koreanus, and the subdominant species was Pungtungia herzi. Among the surveyed fish species, endangered species were Pseudobagrus brevicorpus (rank I) and Cottus hangiongensis (rank II). In addition, migratory fish species were Oncorhynchus keta, Plecoglossus altivelis, and Tribolodon hakonensis. As a result of community analysis, the highest diversity, dominance, richness, and evenness indices were Wangpi, Chuksan, Gokgang, and Janggi Stream respectively. The highest number of species was surveyed in Gokgang Stream (25 species). Alpha diversity, the number of species at each survey point in each stream, was the highest at a survey point in Wangpi Stream (20 species), and beta diversity, species at each stream survey point that does not overlap with nearby survey point, was the highest at survey points in Gokgang Stream (12 species). As a result of the similarity analysis, surveyed streams were divided into four groups: group 1 (Chuksan, Baeknok Stream), group 2 (Uljinnamdae, Wangpi, Yungdeokosip Steam), group 3 (Gokgang Stream), and group 4 (Janggi, Hoeya Stream). This study is expected to serve as basic data for managing the aquatic ecosystem of streams flowing from the Nakdong River region to the east coast.

A Review on the Impact of Vertical Slotted Fish Passages on Fish Populations in River Basins

The interruption of fish migration routes has a negative impact on the health of aquatic populations and ecosystems. To address this issue, vertical seam fishways are designed to assist fish in crossing dams and embankments. This article integrates the concept and design ideas of vertical seam fishways, the impact assessment of vertical seam fishway construction on fish in the watershed, as well as the problems and challenges encountered, by searching and reading relevant materials. The aim is to provide reference for ecological restoration and fish protection in hydraulic engineering.