Fish Biodiversity Research Articles

Examination of the Utility of Environmental DNA Metabarcoding for Monitoring Fish Species in Han Rivr, Korea

Han River in Korea is a crucial water resource and fish habitat. Nonetheless, its biodiversity is declining because of anthropogenic activities, particularly pollution. Fish species sensitive to environmental changes are monitored to conserve biodiversity and pollution monitoring. Fish species can be monitored based on environmental DNA (eDNA) which is released by organisms into the environment eDNA metabarcoding can compensate for the difficulties of collection-based fish monitoring and can be used for efficient monitoring. This study aimed to examine the utility of eDNA metabarcoding for monitoring fish species by performing eDNA metabarcoding of fish 12S rRNA from water samples collected from three locations in the Han River. The results were compared with collection-based survey data from the Water Environment Information System (Ministry of Environment of Korea) from the last three years. The results revealed 32 species that were identified in three locations through eDNA metabarcoding analysis. At all locations, eDNA metabarcoding detected 74.4% of the 43 fish species compared with the collection-based survey data, confirming as a valuable tool for monitoring fish species in Han River. Additionally, eDNA metabarcoding can be used as a tool to compensate for the limitations of collection-based surveys by detecting species with hiding characteristics and nocturnal species that are difficult to detect in collection-based surveys. The results of this study can be used as primary data to contribute to the conservation of fish biodiversity in Han River in the future.

Biodiversity dimensions of fish communities inhabiting coastal muddy bottoms in the Tropical South Atlantic

This study provides insights into the intricate dynamics of coastal muddy bottoms within tropical regions spanning from the Amazon to the São Francisco River estuary. Through species analysis, distinct species pools distributed across the Tropical South Atlantic have been identified, revealing diverse patterns in fish biodiversity that transcend mere species richness and abundance, extending to their functional composition. More precisely, significant variations in taxonomic composition among the studied areas were observed, with differences in species composition and the presence of exclusive species contributing to the rise of unique patterns in functional diversity, partly attributed to differences in biogeographical provinces. Moreover, local processes such as salinization and estuarization also play crucial roles in shaping the taxonomic and functional diversity patterns within coastal muddy bottoms. By acknowledging the distinctive characteristics and ecological significance of these habitats, we can ensure the preservation of fish communities and uphold their crucial roles as vital nursery and fishing grounds.

Anthropogenic–induced environmental and ecological changes in the Nile Delta over the past half-century

Anthropogenic activities over the past half-century have had a negative impact on the wetland ecosystem in the Nile Delta, which provides essential provisioning and regulating services. Therefore, it is crucial to systematically investigate pollution levels and their ecological consequences at both spatial and temporal scales in order to promote sustainable development. In this study, data on metal pollution in the Manzala Lake were compiled through a systematic review of all published literature from 1968 to 2020. Additionally, agricultural data (including land use, pesticide and fertilizer usage, and discharge) and economic data for the same time period were collected to identify the main drivers of pollution. The results indicated an overall increasing trend in heavy metal concentrations during the study period. The average concentrations of metals, arranged in descending order, were as follows: Fe (15,115.5 μg/g) > Mn (722 μg/g) > Zn (115.4 μg/g) > Cu (65.9 μg/g) > Ni (62.5 μg/g) > Cr (58.1 μg/g) > Pb (54.1 μg/g) > Cd (4.7 μg/g) > Hg (0.1 μg/g). A linear regression model revealed that wastewater discharge, water reuse, and the use of pesticides and fertilizers are the main sources of heavy metal pollution in the Manzala Lake. Consequently, there has been a dramatic decrease in the biodiversity of fish and molluscan communities. The study also found a correlation between heavy metal pollution and socio-economic development, highlighting the urgent need for attention to the conservation, management, and sustainable development of the lake.

A fish biodiversity protection based approach for assessing environmental flow regime in rivers

Available environmental flow assessment methods are not able to integrate the impacts of flow regime on the fish biodiversity which means improving these methods is necessary. This study proposes a novel approach to assess environmental flow regime in which the fish biodiversity index is simulated in the structure of the environmental flow assessment for protecting the fish biodiversity values in the case study. Due to considerable impact of water quality parameters as well as physical flow parameters, two combined physical flow and water quality indices were considered as the inputs of simulating fish biodiversity index. Adaptive neuro fuzzy inference system (ANFIS) as well as hydraulic simulation were applied to simulate combined indices of physical flow and water quality. Moreover, a multiple linear regression (MLR) model was utilized for simulating the fish biodiversity index. Due to necessity of simulating natural flow regime in the representative river reach, soil and water assessment tool as a known hydrological tool was applied as well. According to evaluation indices of the case study, ANFIS model as well as SWAT and MLR are reliable to assess environmental flow considering the fish biodiversity. The minimum environmental flow in the study area was assessed 40% of mean annual flow in which the difference between fish biodiversity index between the natural flow and environmental flow is less than 10%. However, significant improvement of water quality is a prerequisite before implementing the proposed environmental flow regime. High computational complexities is one of the weaknesses of the proposed method.

Development of a quantitative colorimetric LAMP assay for fast and targeted molecular detection of the invasive lionfish Pterois miles from environmental DNA

The Mediterranean basin has faced an increased influx of invasive species since the Suez Canal expansion in 2015. The invasive lionfish species, Pterois miles, has rapidly established new populations in the Eastern Mediterranean Sea, impacting local fish biodiversity. Here, we have developed a new, fast (< 35 min) molecular approach to detect and quantify P. miles environmental DNA (eDNA) in combination with a portable device for field-based analysis. Using a species-specific real-time colorimetric loop-mediated isothermal amplification (qcLAMP) for the cytochrome oxidase subunit 1 (COI) gene, we demonstrate a high sensitivity with a limit of detection of 0.002 ng DNA per reaction, equivalent to only 50 copies of the COI gene. The assay is specific to the target in the presence of closely related and co-occurring species, and it is quantitative over five orders of magnitude. We validated the assay using aquarium water samples and further demonstrated its utility on natural eDNA samples collected from locations around the island of Crete where P. miles had been sighted. P. miles was indeed detected in three out of nine locations, two nature reserves and a closed bay. Lack of detection in the remaining locations suggests that populations are still at a low density. We also demonstrate the feasibility of P. miles eDNA qualitative detection directly from the filter used to collect eDNA-containing particles, completely omitting DNA extraction. Overall, we present a new approach for fast and targeted eDNA quantification. The developed LAMP assay together, with the quantitative real-time colorimetric detection approach, open new possibilities for monitoring invasive P. miles in the field.

Determination of Growth Indicators of Tilapia sparrmanii (Smith, 1840) in Molepo Dam, South Africa.

<b>Background and Objective:</b> The sustainable management and conservation of fish biodiversity depends on studying fish biology. In this study, the length-weight relationships and condition factors of <i>Tilapia sparrmanii</i> were observed to gain a better understanding of their ecological and nutritional conditions. This information is crucial for the effective management of fisheries. <b>Materials and Methods:</b> During the study, 100 <i>T. sparrmanii</i> were collected from the Molepo Dam from October, 2022 to March, 2023. This fish's condition factor (CF) and length-weight relationship (LWR) were studied. To determine the size of each fish, the total length was measured using a caliper with a precision of 0.1 mm and the weight using a balance with an accuracy of 0.1 g. Differences were analyzed using ANOVA with the Tukey's <i>post hoc</i> test. A non-parametric Chi-square test was employed to evaluate the differences in sexes each month. <b>Results:</b> Their total length and body weight ranged from 4-15 cm and 0.96-57.96 g, respectively. The study found a strong positive relationship between the length and weight of the fish (r = 0.96). The regression coefficient (b) was more than 3.0, indicating a positive allometric growing rate. The condition factors (K) of males and females were not significantly different (p>0.05). The lowest CF value was observed in March (K = 1.01±0.03) and the highest in December (K = 1.73±0.12). The sex ratio of 1.0 male to 1.15 female was observed, which was significantly different from the theoretical ratio of one male to one female. This suggests that males were not significantly more than females (p>0.05). <b>Conclusion:</b> The study found that <i>T. sparrmanii</i> in Molepo Dam exhibited allometric growth, as evidenced by a strong correlation between length and weight represented by a high "r" value. This fish is in good condition because it has no competition for food due to ecological factors.

Nearshore fish diversity changes with sampling method and human disturbance: Comparing eDNA metabarcoding and seine netting along the Upper St. Lawrence River

Aquatic ecosystems are deteriorating, with the most impacted species and populations having insufficient data to inform conservation and management. Monitoring aquatic biodiversity and evaluating anthropogenic impacts typically rely on time-consuming, logistically challenging, and invasive methods (e.g., seining, trawling or electrofishing). Environmental DNA (eDNA) methods have been touted as an important advancement, especially in fish biodiversity assessment. We compare eDNA metabarcoding and seining methods along a 350 km section of the Upper St. Lawrence River (Canada) for: i) mapping the distribution of invasive and threatened fish species, ii) describing species richness and fish community structure, and iii) assessing the effect of habitat type and anthropogenic degradation of riparian zones on fish community composition and richness. eDNA detected more fish species (n = 67) than seining (n = 38) and revealed higher fish diversity in samples adjacent to intact, natural riparian zones. Fish assemblages were influenced by habitat type according to analyses using eDNA, while no effect of any environmental predictor on fish community composition was found using seining. Altogether, our results support eDNA metabarcoding as a powerful, complementary tool in fish monitoring and testing for the impacts of anthropogenic disturbances.

Freshwater fish diversity from Siberut Island, a small island in the western part of Sumatra, Indonesia

Abstract. Roesma DI, Tjong DH, Aidil DR, Prawira FDL, Saputra A. 2024. Freshwater fish diversity from Siberut Island, a small island in the western part of Sumatra, Indonesia. Biodiversitas 25: 836-845. Indonesia is an archipelagic country with thousands of islands, including small islands with a variety of biodiversity, such as freshwater fish. Data and information on the fish biodiversity of small islands in the western part of Sumatra are limited, including Siberut Island. A study on freshwater fish diversity in Siberut Island was carried out using morphological and molecular methods. The study was conducted on seven rivers in the North and South Siberut Districts, Siberut Island. The study obtained 676 individuals, including 34 species, 26 genera, 16 families, and 10 orders. Oxudecidae is the family with the largest species (8), and Rasbora jacobsoni has the highest number of individuals (341). Species richness ranged from 2 to 18 species per site and was highest in the Srilanggai River. Siberut Island has low-moderate freshwater fish diversity. As many as 90 DNA barcodes of individuals from 34 species have been submitted to the Barcode of Life Data System. Freshwater fish groups do not receive enough attention from local communities and the government because of the richness of marine fish on Siberut Island. Apart from functioning as evidence of species richness, the results of this study are also useful for local communities' education.

Combining eDNA metabarcoding and conventional method in rapid screening of fish diversity in Maros-Pangkep Global Geopark, South Sulawesi, Indonesia

Abstract. Ambeng, Iqram M, Litaay M, Hasyim Z, Moka WJC, Tinungki GM. 2024. Combining eDNA metabarcoding and conventional method in rapid screening of fish diversity in Maros-Pangkep Global Geopark, South Sulawesi, Indonesia. Biodiversitas 25: 819-828. A newly designated geopark by UNESCO, Maros-Pangkep Global Geopark, South Sulawesi, Indonesia owns great geodiversity, exceptional cultural heritage, and high biodiversity. However, the global biodiversity crisis that has hit the earth might also occur in Maros-Pangkep river systems, potentially threatening endemic freshwater fish and all other biota. It has been reported that there is high pressure on the environment along the watershed in the Maros-Pangkep rivers, including a high sedimentation rate downstream, which is linked to extreme erosion upstream and could eventually affect fish populations such as endemic ones. This should prompt a call for the authorities to build a strategy for monitoring and documenting aquatic biota such as fish to preserve biodiversity. Environmental DNA (eDNA) could be considered a method for monitoring fish species based on the DNA traces they shed in the water. Hence, this study aims to use eDNA to survey fish biodiversity in several rivers in the Maros-Pangkep Global Geopark and compare the result against the traditional gillnet method. The results showed that using two methods, 29 fish species in 19 families and 15 orders were obtained from the three rivers. Despite the majority of detected species, 25 species, as the result of using eDNA, 4 species were only detected using a traditional method which eDNA failed to identify. Among those species, several endemic and non-native species were successfully identified by either one or both methods. This could eventually be a suggestion for responsible authorities in biodiversity conservation to combine both approaches to monitor and conserve local biodiversity.

Evaluating the effectiveness of the eRNA technique in monitoring fish biodiversity – A case study in the Qingdao offshore, China

With the continuous intensification of human activities, fish biodiversity has been reduced in the Yellow Sea. Therefore, accurate monitoring methods are crucial for determining fish biodiversity in the target area. The environmental DNA (eDNA) technique has emerged as a promising non-invasive method, but it is prone to false positives. The rapid degradation of environmental RNA (eRNA) has the potential to reduce false positives in the eDNA technique; however, there is limited research on using the eRNA technique to study fish biodiversity. This study aimed to explore a suitable sampling method for extracting sufficient eRNA from seawater samples. Furthermore, we performed a case study in Qingdao offshore, China, to survey fish species and community composition based on the eRNA and eDNA techniques in November 2022 using seawater samples collected from 19 sampling sites. We compared the results with data obtained through traditional field survey (TFS) methods and examined the relationship between fish species and environmental factors. The results revealed a significant overlap between fish species detected by the eRNA and eDNA techniques, with the eRNA technique demonstrating higher sensitivity and positive predictivity, and fewer false positives compared to those of eDNA. Our study highlighted the potential of the eRNA technique as a powerful tool for improving the detection rate of fish species in marine ecosystems.

Interrelationship between limnological parameters of a floodplain lake in Dwarkeshwar river basin and their impact on fish biodiversity

Interrelationship between limnological parameters of a floodplain lake in Dwarkeshwar river basin and their impact on fish biodiversity

Fishes of the Alitash National Park: Taxonomic Accounts with Identification Keys of Fish in Floodplain Rivers of Abbay and Tekeze Basins, Ethiopia

Ethiopia has considerable freshwater potential. Currently, the recognized fish diversity in the country’s freshwater ecosystem is more than 200. Despite the presence of such high fish diversity with considerable economic returns, ichthyofaunal studies on Ethiopian rivers are scarce. Thus, this study aimed to identify and compare ichthyofaunal diversity and distribution in floodplain rivers of the Abbay and Tekeze Basins, Ethiopia. Fish were collected using gillnets, cast nets, hooks, electrofishing, and mosquito nets and identified to the species level. Gillnets had stretched mesh sizes of 4–14 cm with a panel length of 25–75 m and a width of 1.5–2 m per mesh size. They were set in the afternoon (5:00 p.m.) and lifted the following morning (7:30 a.m.). Immediately after capture, fish were preliminary identified in the field and tagged with proper information (e.g., sampling locality and date of collection). Similar fishing efforts were applied at all sampling sites for two dry and two wet months over a period of two years (2018-2019). In the present study, both alpha and beta diversity indices were also examined. Identification keys and an annotated checklist of species were generated for easy naming of the entire fish species in the basins. In the ichthyological collection, 43 fish species with 11 new records from the Ayima, Gelegu, and Shinfa Rivers were identified. The first two rivers in the Abbay Basin were the richest in species and number of individuals. Gelegu River had the highest abundance as well. Generally, this study was conducted in areas where no fish biodiversity studies have been undertaken, and the results obtained from this study could be important for fish biodiversity conservation.

A Metric-Based Few-Shot Learning Method for Fish Species Identification with Limited Samples.

Fish species identification plays a vital role in marine fisheries resource exploration, yet datasets related to marine fish resources are scarce. In open-water environments, various fish species often exhibit similar appearances and sizes. To solve these issues, we propose a few-shot learning approach to identifying fish species. Our approach involves two key components. Firstly, the embedding module was designed to address the challenges posed by a large number of fish species with similar phenotypes by utilizing the distribution relationships of species in the embedding space. Secondly, a metric function was introduced, effectively enhancing the performance of fish species classification and successfully addressing the issue of limited sample quantity. The proposed model is trained end to end on fish species public datasets including the Croatian fish dataset, Fish4Knowledge and WildFish. Compared with the prototypical networks, our method performs more effectively and improves accuracy by 2% to 10%; it is able to identify fish effectively in small samples sizes and complex scene scenarios. This method provides a valuable technological tool for the development of fisheries resources and the preservation of fish biodiversity.

Fish biodiversity of Courtown Cays, seaflower biosphere reserve (Colombian Caribbean): new records and an annotated checklist

Fish biodiversity of Courtown Cays, seaflower biosphere reserve (Colombian Caribbean): new records and an annotated checklist

Predicting downstream transport distance of fish eDNA in loticenvironments.

Environmental DNA (eDNA) is an effective tool for describing fish biodiversity in lotic environments, but the downstream transport of eDNA released by organisms makes it difficult to interpret species detection at the local scale. In addition to biophysical degradation and exchanges at the water-sediment interface, hydrological conditions control the transport distance. A new eDNA transport model described in this paper considers downstream retention and degradation processes in combination with hydraulic conditions and assumes that the sedimentation rate of very fine particles is a correct estimate of the eDNA deposition rate. Based on meta-analyses of available studies, the particle size distribution of fish eDNA (PSD), the relationship between the sedimentation rate and the size of very fine particles in suspension, and the influence of temperature on the degradation rate of fish eDNA were successively modelled. After combining the results in a mechanistic-based model, the eDNA uptake distances (distance required to retain 63.21% of the eDNA particles in the riverbed) observed in a compilation of previous experimental studies were correctly simulated. eDNA degradation is negligible at low flow and temperature but has a comparable influence to background transfer when hydraulic conditions allow a long uptake distance. The wide prediction intervals associated with the simulations reflect the complexity of the processes acting on eDNA after shedding. This model can be useful for estimating eDNA detection distance downstream from a source point and discussing the possibility of false positive detection in eDNA samples, as shown in an example.

Assessment of genetic diversity of freshwater genus Labeo through DNA barcoding and phylogenetic analysis inhabited in the River Indus

ObjectivesGenus Labeo of family Cyprinidae comprising of important group of fish species are known for ornamental purpose, food, extracting oil, medicinal value and for potential viable aquaculture. The present study was conducted to assess the morphometric and molecular identification of freshwater fishes of genus Labeo including Catla catla, Labeo rohita, Labeo calbasu, Labeo gnius, Labeo bata from the three fish resources of River Indus, Punjab, Pakistan. MethodsOut of 75, thirty fish specimen were amplified and sequenced with 650 bp of mitochondrial COI gene for the evaluation of fish biodiversity, management and conservation by using different bioinformatics techniques. ResultsMaximum and minimum genetic divergence between fishes of C. catla, L. calbasu, L. boga, L. gonius and L. rohita, were 0.052 to 0.105, respectively. Highest divergence was found between Labeo bata and Labeo rohita. Interspecific mean distance was found higher than intraspecific distance. In nucleotide base composition, AT contents was higher than GC contents indicated the clear pattern of anti-G bias. Transition rate was k1 = 8.84 for purines and transversional rate was k2 = 15.47 for pyrimidines with transition/transversion bias R = 5.62. Tajima D test and nucleotide diversity was measured D = 1.382883 and π = 0.049981 respectively. Positive value of D indicated a strong selective pressure and lack of population expansion. Thirty species were identified with e-value 0.0 and similar identity 99.85 %–100 % with maximum 600 bp length. Phylogenetic tree revealed two major clades with 95 % high bootstrap values identity showed closet relationship among these species. ConclusionsCurrent study supported the efficacy of the COI gene for the species identification in River Indus and develop the concept for establishing Pakistani fish gene bank which is still needed.

Temporal change in urban fish biodiversity-Gains, losses, and drivers of change.

Our aim was to examine temporal change in alpha and beta diversity of freshwater fish communities in rivers that have urbanized over the same period to understand the influence of changes in land use and river connectivity on community change. We used biological (2001-2018), land use (2000-2015), and connectivity data (1987-2017) from Toronto, Ontario, Canada. We used linear mixed effects models to determine the strength of upstream land use, connectivity, and their changes over time to explain temporal change in alpha and beta diversity indices. We examined beta diversity using the temporal beta diversity index (TBI) to assess site-specific community change.The TBI was partitioned into gains and losses, and species-specific changes in abundance were assessed using paired t-tests. There were more gains than losses across the study sites as measured by TBI. We found little to no significant differences in species-specific abundances at aggregated spatial scales (study region, watershed, stream order). We found different relationships between landscape and connectivity variables with the biodiversity indices tested; however, almost all estimated confidence intervals overlapped with zero and had low goodness-of-fit. More fish biodiversity gains than losses were found across the study region, as measured by TBI. We found TBI to be a useful indicator of change as it identifies key sites to further investigate. We found two high value TBI sites gained non-native species, and one site shifted from a cool-water to warm-water species dominated community, both of which have management implications. Upstream catchment land use and connectivity had poor explanatory power for change in the measured biodiversity indices. Ultimately, such spatial-temporal datasets are invaluable and can reveal trends in biodiversity useful for environmental management when considering competing interests involved with urban sprawl in the ongoing "Decade on Restoration."

Benchmarking fish biodiversity of seaports with eDNA and nearby marine reserves

AbstractCoastal areas offer a diversity of habitats providing refugia and nursery for fish, promoting their biodiversity and associated contributions to people. Yet, natural coastlines are replaced by artificial infrastructures such as seaports and the influence of this artificialization on fish biodiversity remains poorly known. Here, we assessed fish biodiversity indicators using environmental DNA metabarcoding inside seaports and adjacent natural habitats including no‐take marine reserves. We found that species assemblages within seaports were primarily influenced by their area and habitat. We detected a similar species richness in seaports and reserves during lockdown, but seaports host more threatened species than natural habitats. Yet, species turnover between seaports was lower than between natural areas, reflecting biotic homogenization. Seaport managers should consider that complexifying artificial infrastructures could increase habitat diversity and coastal fish biodiversity. Our study illustrates that eDNA‐based indicators can be integrated in management and policy applications toward greener marine artificial infrastructures.

Heat shocks during egg incubation led to developmental, morphological, and behavioral differences in Arctic charr (Salvelinus alpinus).

Temperature variation is affecting fish biodiversity worldwide, causing changes in geographic distribution, phenotypic structure, and even species extinction. Incubation is a critical stage for stenothermic species, which are vulnerable to large temperature fluctuations, and its effects on the phenotype at later developmental stages are understudied, despite the fact that the phenotype being essential for organism ecology and evolution. In this study, we tested the effects of heat shocks during the embryonic period on the phenotype of Arctic charr (Salvelinus alpinus). We repeatedly quantified multiple phenotypic traits, including morphology, development, and behavior, over a period of 4 months, from hatching to juvenile stage in individuals that had experienced heat shocks (+ 5°C on 24 h, seven times) during their embryonic stage and those that had not. We found that heat shocks led to smaller body size at hatching and a lower sociability. Interestingly, these effects weakened throughout the development of individuals and even reversed in the case of body size. We also found an accelerated growth rate and a higher body condition in the presence of heat shocks. Our study provides evidence that heat shocks experienced during incubation can have long-lasting effects on an individual's phenotype. This highlights the importance of the incubation phase for the development of ectothermic organisms and suggests that temperature fluctuations may have significant ecological and evolutionary implications for Arctic charr. Given the predicted increase in extreme events and the unpredictability of temperature fluctuations, it is critical to further investigate their effects on development by examining fluctuations that vary in frequency and intensity.

Assessing electrofishing effort required to estimate species richness of fishes in nonwadeable rivers of Alabama, USA

AbstractObjectiveMuch of the fish biodiversity in the southeastern USA is found in lotic systems, but assessment of fish community structure in large nonwadeable rivers has lagged compared to streams. Sampling designs that adequately estimate species richness are a prerequisite to creating bioassessment metrics but thus far has not been attempted in highly biodiverse rivers in the southeastern USA east of the Mississippi River.MethodsFish communities in four nonwadeable rivers across Alabama spanning catchments of 2046–57,415 km2 were sampled using electrofishing in summer and fall of 2015 and 2016. All rivers were sampled during day; two rivers were also sampled at night to assess diel changes in species accumulation.ResultIn total, 55,239 fishes were collected across rivers, representing 106 species in 24 families. Species collected continued to increase as sampling increased in all river‐season combinations, rarely displaying an asymptote. Species generally accrued more quickly and accumulation curves showed more tendency to asymptote in fall than summer in all but the largest river. Species accumulated faster at night than during the day in both rivers during summer but was similar between diel periods in fall. On average, 95% of the species observed were collected in eight subreaches in fall but not until nine during summer; however, observed number of species was generally one to six species lower than mean estimates of true species richness. Sampling efforts collected approximately similar species assemblages across transects, years, season, and diel periods. Extrapolation of species accumulation curves suggested that 6–17 km of sampling distance would be required to collect all species present.ConclusionResults of this study demonstrate that assessing fish communities in species nonwadeable rivers requires an inordinate amount of sampling effort, which may be unattainable for many agencies. Further study is warranted to develop innovative solutions to overcome these logistical challenges.