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Endangered Fish, Rivers at Risk: Spatial Aspects of Freshwater Biodiversity Conservation

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A special issue of Water (ISSN 2073-4441). This special issue belongs to the section "Biodiversity and Functionality of Aquatic Ecosystems".

Deadline for manuscript submissions: closed (1 May 2023) | Viewed by 15496

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Dr. Aaron Koning

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Guest Editor

Department of Biology and Global Water Center, University of Nevada, Reno, NV, USA
Interests: conservation biology; ecosystem ecology; rivers; aquatic ecology; fish ecology; freshwater ecology; aquatic ecosystems; community structure; field sampling; freshwater biology; stream ecology; freshwater fish ecology; limnoecology; electrofishing; experimental biology; freshwater fisheries

Dr. Zeb Hogan

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Guest Editor

Department of Biology, University of Nevada, Reno, NV 89557, USA
Interests: conservation biology; aquatic ecology; fisheries; environmental education; science communication
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Special Issue Information

Dear Colleagues,

Freshwater ecosystems support over 18,000 fish species, a quarter of all known vertebrates, as well as thousands of other animal and plant species. These critical ecosystems, and the diversity of life they support, are highly imperiled by numerous, interacting threats. Habitat degradation, flow modification and fragmentation, non-native species introductions, pollution, overexploitation, and climate change have resulted in IUCN threatened status for nearly one-third of all listed freshwater fish species. While the threats facing freshwaters and freshwater fishes are well documented, their continued decline suggests current conservation strategies provide insufficient protection for many threatened fish populations. In recent years, there has been a growing recognition of the benefits of protecting riverine habitats and conserving connectivity for aquatic biodiversity. The aim of this Special Issue is to both highlight spatial approaches for the protection of threatened freshwater fishes and to identify the challenges to wider implementation of these strategies. Successful protection for threatened freshwater fishes, and other species, will require continued development of diverse conservation strategies, including spatial protections. By identifying cases where durable river/habitat protection has effectively protected at-risk fish populations, and conversely, where spatial protection (or better understanding of spatial factors) is needed or could be applied, this Special Issue will add to the portfolio of tools available for effective global freshwater conservation.

Contributions are welcome on topics such as the past, present, and future status of endangered freshwater fishes and their habitats, spatial aspects of fish natural history and population genetics, migration and ecological connectivity, explorations of the importance of scale and ecosystem process when considering conservation approaches and outcomes, scale and spatial components of threats and human impacts, single species vs. ecosystem-based approaches, and obstacles and approaches to transboundary management, policy, and conservation. Commentaries, short communications, literature reviews, field-based research, and case studies are all welcome.

Dr. Aaron Koning
Dr. Zeb Hogan
Guest Editors

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Keywords

conservation
biodiversity
conservation biology
fish biology
fisheries science
fisheries management
fish ecology
ecosystem ecology
aquatic ecology
freshwater-protected areas
fish reserves

Published Papers (8 papers)

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Research

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19 pages, 2617 KiB

Open AccessArticle

Assessing the Movements, Habitat Use, and Site Fidelity of the Giant Freshwater Whipray (Urogymnus polylepis) with Acoustic Telemetry in the Maeklong River, Thailand

by Thanida Haetrakul, Teresa Campbell, Chayanis Daochai, Nitiwadee Keschumras, Tanatporn Tantiveerakul, Zeb Hogan and Nantarika Chansue

Water 2023, 15(13), 2311; https://doi.org/10.3390/w15132311 - 21 Jun 2023

Cited by 1 | Viewed by 1575

Abstract

We used acoustic telemetry to assess site fidelity, movement patterns, and habitat use within the lower Maeklong River, Thailand, by 22 giant freshwater whipray Urogymnus polylepis. This study is the first of its kind for this rare, endangered species, and it begins to fill critical information gaps about its ecology and life history. Study animals were tagged subcutaneously in the dorsal area with acoustic transmitters and tracked for 12 months using a fixed array of eight receivers. Receivers were positioned within an 18 rkm section of the Maeklong, starting approximately 4 rkm upstream from the mouth. We calculated individual residency indices, tracked longitudinal movements, and assessed annual and seasonal patterns of site use. We also investigated spatial use patterns, diel activity patterns, and relationships of temperature and site fidelity. We detected 86% of our tagged whiprays, 53% of which were detected for the majority of the study period. Whiprays exhibited high site fidelity across seasons. Individuals made long longitudinal movements within the site for much of the study period but seemed to remain closer to the estuary during the second half of the rainy season and early winter. All receivers had large numbers of detections, but upstream receivers were visited for longer time durations than downstream receivers. A receiver in the middle of the study area had the highest detection rate, but low detection durations, suggesting that this receiver is in a migration corridor. A mix of immature and mature males and females was present in the site throughout the study period, suggesting that this area is not exclusively a breeding or nursery site. However, the high site fidelity suggests that this is an important aggregation site for the species. Effective conservation measures may include conservation zones and a shrimp reintroduction program upstream, ensuring fish passage through the middle of the site, and regulating traffic and pollution downstream. We found acoustic telemetry to be an effective study method and encourage its use to improve understanding of the giant freshwater whipray. Full article

(This article belongs to the Special Issue Endangered Fish, Rivers at Risk: Spatial Aspects of Freshwater Biodiversity Conservation)

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9 pages, 1945 KiB

Open AccessCommunication

World Heritage, Hydropower, and Earth’s Largest Freshwater Fish

by Dana Lee, Jackman C. Eschenroeder, Lee J. Baumgartner, Bunyeth Chan, Sudeep Chandra, Seila Chea, Sothearoth Chea, Chheana Chhut, Elizabeth Everest, Radong Hom, Kong Heng, Stefan Lovgren, Sinsamout Ounboundisane, Wayne Robinson, Lykheang Seat, Sobot Soth and Zeb S. Hogan

Water 2023, 15(10), 1936; https://doi.org/10.3390/w15101936 - 20 May 2023

Cited by 2 | Viewed by 4291

Abstract

The Mekong River is one of the most biodiverse, productive rivers in the world, supporting more than 1000 fish species and the livelihoods of tens of millions of people. The spatial dynamics and population status of many Mekong fish species, especially megafishes, are poorly understood. Therefore, this information is rarely incorporated into environmental risk assessments for large infrastructure projects, such as mainstream hydropower developments, which have been accelerating rapidly in the Mekong Basin. In this study, we present initial findings from the ongoing, collaborative, transnational acoustic telemetry monitoring of nearly 300 tagged fishes representing 27 species, which yield important insights into the potential impacts that proposed hydropower dams would have on populations of ecologically and economically important fish species. Included in these data are more than ten months of hydrophone records tracking the location of a 300 kg giant freshwater stingray, Urogymnus polylepis (Bleeker, 1852), currently the world’s largest known freshwater fish, used to detect its migration behavior and distribution patterns. The telemetry data, combined with fisher surveys used to gather local ecological knowledge, provide evidence that the proposed dams would fragment the existing populations of this iconic species as well as those of other fish species that support river food web balance and local food systems. Furthermore, the existence of giant freshwater stringray populations and other unique megafauna reinforces the universal natural heritage value of the stretch of the Mekong River between the Lao People’s Democratic Republic/Cambodia border and the city of Kratie. This stretch of river is located between two proposed megadams, the 900 MW Stung Treng Dam and the 2300 MW Sambor Dam. However, the Cambodian Ministry of Environment has also proposed this area for designation as a UNESCO World Heritage Site (Biosphere Reserve). The documentation of the movement of migratory fishes through this reach of the river using acoustic telemetry, the surprising discovery of the world’s largest freshwater fish, the potential threat posed by dam construction, and the management ramifications of UNESCO World Heritage Site designation underscore the importance of scientific research and community involvement in landscape-scale development decisions. The decisions made today will affect the fate of this global biodiversity hotspot, the world’s most productive inland fisheries, and the livelihoods of millions of people throughout the Lower Mekong Basin. Full article

(This article belongs to the Special Issue Endangered Fish, Rivers at Risk: Spatial Aspects of Freshwater Biodiversity Conservation)

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16 pages, 4402 KiB

Open AccessArticle

Spatial Conservation Assessment for Native Fishes in the Lahontan and Central Nevada Basins, USA

by Daniel C. Dauwalter, Eric Miskow and Chris Crookshanks

Water 2023, 15(6), 1087; https://doi.org/10.3390/w15061087 - 12 Mar 2023

Viewed by 1896

Abstract

Freshwater biodiversity is declining faster than terrestrial and marine biodiversity. The protection and restoration of aquatic habitats are based, in part, on stemming this decline. We conducted a spatial conservation assessment of native fishes in the Lahontan and central Nevada basins using core-area zonation. The complementarity-based assessment yielded a landscape value (rank) of all subwatersheds (12-digit hydrologic unit code; ~12,000 ha) whereby high-ranking subwatersheds, as a set, maximized the representation of all native species, subspecies, and the within-species ecological diversity of salmonids, while accounting for aquatic connectivity and risk of aquatic habitat degradation. The high-ranking subwatersheds encapsulated small patches of habitat inhabited by endemic desert fishes, as in the Ash Meadows National Wildlife Refuge. They also highlighted clusters of high-value subwatersheds, such as in the Truckee River watershed that has extant populations of, and historical habitat for, Lahontan cutthroat trout in its headwaters, with species such as the mountain whitefish with migratory life histories, and endemic cui-ui, Chasmistes cujus, at Pyramid Lake—a terminal lake. Both the Truckee River headwaters and Pyramid Lake have been recipients of ongoing native fish conservation efforts. The landscape rankings will be used by the Desert Fish Habitat Partnership to inform regional conservation investments, and the rankings are available for broader use by resource agencies working on native fish conservation at landscape scales. Full article

(This article belongs to the Special Issue Endangered Fish, Rivers at Risk: Spatial Aspects of Freshwater Biodiversity Conservation)

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15 pages, 1355 KiB

Open AccessArticle

The Ichthyofauna of the Bednja River, Ichthyological ‘Hot Spot’ in the Danube Basin—Exceptional Diversity under Strong Threats

by Ivana Buj, Sara Pleše, Lucija Onorato, Zoran Marčić, Perica Mustafić, Davor Zanella, Marko Ćaleta, Lucija Ivić, Lucija Novoselec, Nikola Renić, Sven Horvatić, Roman Karlović and Goran Tvrdinić

Water 2023, 15(2), 311; https://doi.org/10.3390/w15020311 - 11 Jan 2023

Cited by 2 | Viewed by 1312

Abstract

The Bednja River is the longest river flowing with its full course exclusively through Croatia and one of the largest right tributaries of the Drava River, which belongs to the Danube River basin. Due to the variety of habitats present within the course of the Bednja River, as well as older literature reports, it can be expected that this river harbors a high number of freshwater fish species and would likely benefit from conservation and preservation efforts. We compiled and analyzed the existing literature data on the Bednja River fish communities and performed field investigations at various localities on this river in order to describe the current structure of its freshwater fish fauna and monitor changes induced by human activities. Our results corroborate the presence of a rich and diverse fish community. Moreover, with 36 native species, the Bednja River harbors one of the richest fish communities in Croatia as well as in the Danube basin. Unfortunately, modifications of the native fish community were evident in the form of local extinctions, reductions in the population abundance of several native species and the presence of non-native species. Habitat degradation and fragmentation were identified as the most serious threats provoking negative effects on the native fish populations, followed by predatory and competitive effects of invasive species. Full article

(This article belongs to the Special Issue Endangered Fish, Rivers at Risk: Spatial Aspects of Freshwater Biodiversity Conservation)

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13 pages, 869 KiB

Open AccessArticle

Dispersal and Survival of Captive-Reared Threatened Fishes in a Tonle Sap Lake Reserve

by Teresa Campbell, Peng Bun Ngor, Bunyeth Chan, Jackman C. Eschenroeder, Elizabeth Everest, Sudeep Chandra, Seila Chea, Kakada Pin, Samol Chhuoy, Soksan Chhorn, Sothearith Soem, Mecta Sup, Chheng Phen, Hoy Sreynov, Thay Somony, Chheana Chhut and Zeb S. Hogan

Water 2022, 14(19), 2995; https://doi.org/10.3390/w14192995 - 23 Sep 2022

Cited by 2 | Viewed by 2280

Abstract

The Tonle Sap Lake in Cambodia supports several species of threatened megafish and contains one of the largest networks of freshwater fish reserves in the world. Despite these traits, this system remains understudied in terms of its utility for endangered fish conservation and restoration. This study was the first of a series of planned fish releases designed to test the effectiveness of conservation supplementation programs in the Tonle Sap Lake. In March 2022 (during the dry season), 1582 captive-reared fishes, including 1538 striped catfish Pangasianodon hypopthalmus, 42 giant barb Catlocarpio siamensis, and two Mekong giant catfish Pangasianodon gigas, were tagged and released into a 986-hectare fish reserve to assess post-release dispersal and survival. Brightly colored external tags with unique identification numbers were used to facilitate tag returns. A high-profile release event was held to raise awareness about the activity, bringing attention to the importance of fish reserves and endangered species conservation, and disseminating information about the research and tag return and reward program. This, in concert with other efforts, served to be an important education and outreach tool and increased tag return rates. We found that mortality from fishing was rapid and very high. Nineteen percent of released fishes were recaptured in the first 2 days after the fish release, and 46% were recaptured by day 83 after the release, indicating intense fishing pressure on the Tonle Sap Lake fisheries. Eighty percent of recaptured fishes were caught in stationary gill nets, most within 10 km of the release site. Fishing mortality rates were independent of fish size or source (pond-reared or cage-reared). Environmental DNA (eDNA) was found to be capable of detecting each of these species’ presence in the water at the release site and could prove to be a useful tool for endangered species monitoring and restoration. Future research should explore alternative release timing, release location, and other methods of increasing post-release survival. Ultimately, underlying sources of mortality, especially fishing, will need to be addressed for conservation supplementation programs to succeed in the Tonle Sap Lake. Conservation supplementation should not be viewed as a substitute for more fundamental conservation measures, such as maintenance of environmental flows, preservation of ecological connectivity, and science-based fisheries management. Full article

(This article belongs to the Special Issue Endangered Fish, Rivers at Risk: Spatial Aspects of Freshwater Biodiversity Conservation)

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22 pages, 6336 KiB

Open AccessArticle

Deep Pools: Ecological Sanctuaries for Steindachneridion melanodermatum, a Large Endemic and Endangered Pimelodid of the Iguaçu River

by Lucileine de Assumpção, Maristela Cavicchioli Makrakis, Jhony Ferry Mendonça da Silva, Karane Allison Silvestre de Moraes, Suelen Fernanda Ranucci Pini, Patrícia Sarai da Silva, Elaine Antoniassi Luiz Kashiwaqui, Eduardo Gentil, Lenice Souza-Shibatta, Oscar Akio Shibatta and Sergio Makrakis

Water 2021, 13(12), 1700; https://doi.org/10.3390/w13121700 - 19 Jun 2021

Cited by 4 | Viewed by 3407

Abstract

Steindachneridion melanodermatum, an endemic and endangered species, is the largest catfish in the Lower Iguaçu River basin. Currently, the wild population of this species no longer exists in most of this basin, probably due to the loss of habitat by successive hydroelectric dams. This study evaluated the spatial distribution and abundance of S. melanodermatum in the last free-flowing river stretch of approximately 190 km downstream from the Salto Caxias Dam, upstream of the Iguaçu Falls, as well as some tributaries. Hydroacoustic and fishing campaigns were performed between September 2010 to December 2016 to characterize the preferred habitat. A total of 180 specimens was sampled with higher abundances in a protected area near Iguaçu Falls in the Iguaçu National Park. Twenty-four deep pools were identified with maximum depths ranging from 5 to 25 m: 21 pools were along the main channel of the Iguaçu River, and three pools were in tributaries. Deep pools are preferential habitats for this species, especially the deep pool called Poço Preto (P23) and its surroundings. Conservation strategies are required to protect these habitats and prevent S. melanodermatum from becoming extinct, such as establishing deep pools as ecological sanctuaries, intensifying the inspection of illegal fishing, and maintaining dam-free tributaries. Full article

(This article belongs to the Special Issue Endangered Fish, Rivers at Risk: Spatial Aspects of Freshwater Biodiversity Conservation)

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15 pages, 15575 KiB

Open AccessReview

A Review of the Conservation Status and Ecology of the Giant Freshwater Whipray (Urogymnus polylepis) across Its Known Distribution

by Teresa Campbell, Sinsamout Onboundisane, Heng Kong and Zeb S. Hogan

Water 2023, 15(13), 2487; https://doi.org/10.3390/w15132487 - 06 Jul 2023

Cited by 3 | Viewed by 2233

Abstract

The giant freshwater whipray is a large-bodied stingray species that is listed as endangered across its known range from India through Southeast Asia. However, little is known about the species’ ecology, biology, and conservation status. We reviewed all available literature, articles, and reports on the species found through database and internet searches in order to consolidate and update information on the giant freshwater whipray. We found that remarkably little research has been done, and most existing information on the species is derived from fisher catch reports. Whiprays of 300 kg or more have been reported in most countries where it occurs. The available evidence suggests that this species is endangered across its range by numerous threats, including fishing, bycatch, bottom trawls, pollution, and habitat destruction and fragmentation. Various reports indicate declines in population size, genetic diversity, and body size. Relatively stable populations may persist in the Maeklong River, Thailand, the Mekong River in Cambodia, and insular Southeast Asia. More work is needed to understand the species’ spatio-temporal distribution, reproductive behavior, migration patterns, and general ecological and biological characteristics in order to inform effective management and conservation plans. Due to difficulties in sampling this rare species and monitoring fisher catches, partnership and collaboration with all stakeholders, including local fishers, government officials, and researchers, is essential to produce conservation gains for the giant freshwater whipray. Full article

(This article belongs to the Special Issue Endangered Fish, Rivers at Risk: Spatial Aspects of Freshwater Biodiversity Conservation)

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21 pages, 711 KiB

Open AccessEditor’s ChoiceReview

Hydropower Dam Development and Fish Biodiversity in the Mekong River Basin: A Review

by Ian G. Baird and Zeb S. Hogan

Water 2023, 15(7), 1352; https://doi.org/10.3390/w15071352 - 01 Apr 2023

Cited by 7 | Viewed by 4231

Abstract

Over the last few decades, considerable concern has been expressed about the threat of Mekong River Basin hydropower dams to a range of important freshwater riverine fisheries, particularly for fish that seasonally migrate long distances. However, much less attention has been given to the threat of hydropower dams to fish biodiversity in the high-diversity Mekong River Basin, the focus of this paper. Through reviewing the existing state of knowledge regarding Mekong River Basin fish biodiversity, and threats to it, we argue that even though no species are definitively known to have been extirpated from the Mekong River Basin to date, hydropower dam development and various other developments nevertheless pose a serious threat to fish biodiversity. Indeed, dams typically significantly block fish migrations and fish larvae distribution, cause river fragmentation, fundamentally alter river hydrology, and change water quality, all factors that have the potential to intersect with each other and lead to significant species extirpation and extinction, or in some cases, functional extinction, when a small population remains but the important larger population is lost permanently. The circumstances are further exacerbated by the lag time between impact and when that impact becomes evident, cumulative impacts, a lack of consistent data collection, including the collection of base-line data, and insufficient post-project research related to biodiversity. We contend that much more could and should be done to ensure that the Mekong River basin’s exceptional fish biodiversity is not variously diminished and destroyed during the coming years. Full article

(This article belongs to the Special Issue Endangered Fish, Rivers at Risk: Spatial Aspects of Freshwater Biodiversity Conservation)

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