Paradigm shifts in fish conservation: moving to the ecosystem services concept

Various factors constrain the existence and development of inland fishes and fisheries, such as pollution, habitat degradation, alien invasive species, local user conflicts, low social priority and inadequate research and funding. In many cases, however, degradation of the environment and loss of aquatic habitat are the predominant concerns for the conservation of freshwater aquatic biota. The need for concerted effort to prevent and reduce environmental degradation, as well as protection of freshwater fishes and fisheries as renewable common pool resources or entities in their own right, are the greatest challenges facing the conservation of fishes in inland waters. Unfortunately, traditional conservation practices such as regulation of exploitation, protected areas and habitat restoration have failed to arrest the alarming increase in number of threatened freshwater fish species worldwide. This paper examines the shifting paradigm of fisheries management from rule-based regulation, through fishery enhancement towards the ecosystem approach to fisheries, with reference to inland waters, and how the emerging concept of ecosystem services coupled with traditional fish conservation management practices, institutional restructuring and integrated management planning should provide a more sustainable thrust to formulation and promotion of fish conservation initiatives.     

River inter linking in India: status,issues, prospects and implications on aquatic ecosystems and freshwater fish diversity

India is a vast country in terms of natural resources and considered one of the mega- biodiversity countries in the world. The freshwater aquatic resources of the different river basins are unevenly distributed in space and time and the country is suffering from the increasing population and shortage of all kind of natural resources like water. To fulfill the water demand and mitigate flood and drought, Indian Government has been planning a huge scheme encompassing the Himalayas and most of India, by linking all major rivers through interlinking canals systems and building several dams. Though the concept of interlinking of rivers is novel and new in India, it had rather initiated long back in other countries of ancient civilization. This is considered as one of the options to remedy spatial mismatch in water availability and demand. To overcome those, National Water Development Agency (NWDA) has taken up massive project and nearly 30 links have been proposed to interlink the major rivers. The Government of India has approved the country’s first river interlinking project on Ken–Betwa and a MOU has been signed among the states of Uttar Pradesh and Madhya Pradesh and the Union Government. The feasibility report of most of the links have been completed and detailed project reports of Ken–Betwa River link is expected to be finalized soon. Our study indicated presence of rich fish diversity and threatened fishes in river Betwa and improved aquatic environment in river Ken which makes it a high priority area in view of proposed interlinking. The current state of knowledge indicates that large dams, interbasin transfers and water withdrawal from rivers have many negative as well as positive impacts on freshwater aquatic ecosystem. As regards to the impact on fish and aquatic biodiversity, there could be positive as well as negative impacts. The present paper is aimed at explaining and synthesizing the long term plan and its implications, creating baseline database, requirement of appropriate technology, manpower and related issues especially with reference to riverine aquatic ecosystem and conservation of fish biodiversity.     

Studies on species of fungi associated with mycotic infections of fish in a Nigerian freshwater fish pond

A survey was carried out on the species of fungi associated with mycotic infections of fish in a Nigerian freshwater fish pond. A total of 24 fungal species belonging to 6 genera of aquatic phycomycete were isolated from the infected fishes. Achlya racemosa, Aphanomyces laevis, Dictyuchus sterile, Saprolegnia ferax, S. litoralis and S. parasitica had 100% frequency of occurrence amongst the infected fishes. There were similarities in the species of fungi isolated from the infected fishes in the fish pond and those isolated from the hatchery. Of the infected fishes, Clarias lazera had the highest number of fungal isolates. It was followed by Tilapia zilli, then by Chanos chanos, Ethmalosa fimbriata and finally by Cyprinus carpio. The implications of the results obtained on the development of fish farming in Nigeria are discussed.     

Freshwater fish biodiversity in the River Ganga (India): changing pattern, threats and conservation perspectives

The river Ganges is the largest river in India and the fifth longest in the world. Although, many studies on fish ecology and systematic have been conducted largely to improve fisheries but fish diversity and their distribution pattern from conservation point of view have never been adequately addressed in the Ganges. In this connection, current distribution and abundance of freshwater fishes of river Ganges was studied and assessed from April 2007 to March 2009. We documented and described 143 freshwater fish species in the all stretches of the river which is higher than what was reported earlier. Some species were observed with shift in their distribution ranges. First time, a total of 10 exotic fishes, including Pterygoplichthys anisitsi, which has never been reported from India found in the Ganges. Alterations of the hydrological pattern due to various types of hydro projects was seems to be the largest threat to fishes of Ganges. Indiscriminate and illegal fishing, pollution, water abstraction, siltation and invasion of exotic species are also threatening the fish diversity in the Ganges and as many as 29 species are listed under threatened category. The study advocates a need to identify critical fish habitats in the Ganga basin to declare them as conservation reserves to mitigate the loss of fish diversity from this mighty large river.     

Impact of terrestrial protected areas on the fish diversity and habitat quality: Evidence from tropical river Pranhita,India

The conservation and management of inland fish and freshwater ecosystems immensely contribute to global sustainable development. The existing ‘Protected Area’ (PA) network does not represent freshwater resources well and seldom considers its fish communities, while designating PAs. A study was undertaken to quantitatively assess the role played by the three terrestrial PAs (IUCN category IV) in conserving fish diversity and preserving habitat quality in the river reaches bordering the three PAs of the river Pranhita. It is a unique river system in the Indian Deccan Plateau in terms of fish diversity and community structure. Field surveys were conducted during the non-monsoon and monsoon seasons in 2020–21, that recorded 53 species including endemic and threatened fishes from river Pranhita, which represent more than one-third the number of fish species of Telangana state. The higher diversity and lower dominance index value (p < 0.01) reported in PAs compared to Eco Sensitive Zones and unprotected areas during the non-monsoon season indicate the role of intact physical habitat in providing refuges to the fish species in monsoon dependent tropical rivers. The optimal water quality revealed no significant difference (p > 0.0001) between protected and unprotected river reaches, and healthy biotic integrity assessed on the basis of fish community structure was attributed to the contiguous flow and less anthropogenic disturbance. This study supports that it can be considered as a representative zone for the conservation and protection of indigenous and endemic fish species of the Godavari Basin. The results concluded that the scope of the terrestrial PA network in India could be potentially extended to their bordering aquatic ecosystems, especially rivers to maintain pristine habitat conditions and conserve the fish genetic resources to ensure the flow of ecosystem services.     

Alien fish species in Indian inland wetlands: current status and future challenges

Although wetlands are well-recognized for their biological, ecological, cultural, hydrological, recreational, socio-economic and educational values, still they are facing severe anthropogenic pressure in the form of habitat destruction, pollution, overexploitation of resources and the invasion of alien species. India is bestowed with several natural and man-made wetlands which support rich aquatic biodiversity with high degree of endemism, especially fish diversity. Zoological Survey of India reported that, inland wetlands alone support 1027 species of fishes with more biological, nutritional and economic values. However, for the past three centuries Indian wetlands are witnessing continuous introduction of exotic fishes. According to available reports, 31 aquaculture species, 600 ornamental varieties and 2 species of larvicidal fish have been introduced. Surfacing reports confirmed that among the introduced fishes nearly 55 fish species established a sustainable reproductive population in several inland wetlands (i.e. wild) including in the biodiversity hotspots. Among the 55 the National Biodiversity Authority of India has declared 14 species as invasive. Though, there are no comprehensive studies available in India about the impacts of invasive alien species on its ecosystem and food security. In addition, researchers are of the opinion that the ongoing climate change, river linking projects, Genetically Improved Farmed Tilapia (GIFT) project and ornamental trade will exacerbate the invasive issues in future. India is thus in a position to develop new robust policy and research guidelines on the exotic species issues. Cooperation among different stakeholders and common public is the need of the hour, else India will lose its unique aquatic diversity and also face huge socio-economic problems.

     

In-stream behaviour of threatened fishes and their food organisms based on remote video monitoring

Can remote underwater video be used to investigate the in-stream behaviour of small fishes and decapods? Diel activity of two threatened freshwater fishes (Macquaria australasica and Gadopsis bispinosus), a palaemonid prawn and an atyid shrimp, was established from remote underwater video in a pool of an upland stream in the current study. Decapods and large fishes (>5 cm TL) were nocturnal, whereas, small fishes (<5 cm TL) were diurnal. The suitability of using underwater video to quantify short-term (seconds) behavioural interaction among individuals was also demonstrated, with early-juvenile-phase Gadopsis bispinosus exhibiting interference competition on 35% of occasions when two or more individuals were observed. This study demonstrates that remote underwater video is useful for observing the in-stream behaviour of threatened freshwater fauna where other techniques are not viable, and presents sub-sampling of video as a means of reducing video processing time in assessing fish diel activity patterns.     

Elevated river discharge enhances the immigration of juvenile catadromous and amphidromous fishes into temperate coastal rivers

Anthropogenic alterations to river flow regimes threaten freshwater biodiversity globally, with potentially disproportionate impacts on species that rely on flow cues to trigger critical life history processes, such as migration for diadromous fishes. This study investigates the influence of river discharge on the abundance of juvenile fish moving into rivers by four temperate catadromous or amphidromous species (common galaxias Galaxias maculatus, spotted galaxias Galaxias truttaceus, climbing galaxias Galaxias brevipinnis and the threatened Australian grayling Prototroctes maraena). Fyke netting or fishway trapping was used to catch juvenile fish moving from estuaries into freshwater in five coastal waterways in south-eastern Australia during the spring migratory period. There was a positive relationship between the probability of high catch rates and mean discharge in September. We also found a positive relationship between discharge and the number of recruits captured 22–30 days later in a flow stressed system. In addition, day-of-year had a strong influence on catch rates, with the peak abundance of juveniles for three species most likely to occur midway through the sampling period (spotted galaxias in October, climbing galaxias in late October and Australian grayling in late October and early November). Our study shows that higher magnitudes of river discharge were associated with increased catches of juvenile catadromous and amphidromous fishes. With a limited supply of environmental water, environmental flows used to enhance immigration of these fishes may be best targeted to maintain small amounts of immigration into freshwater populations in waterways or years when discharges are low and stable. When there are natural, large discharge volumes, relatively large numbers of juvenile fish can be expected to enter coastal waterways and during these times environmental flows may not be required to promote immigration.     

Impacts of Alien Invasive Species on Freshwater Fauna at Risk in Canada

Freshwater aquatic organisms in North America are disproportionately imperilled when compared to their terrestrial counterparts due to widespread habitat alteration, pollution, overexploitation and the introduction of alien species. In this review, we examine the threat factors contributing to the endangerment of freshwater fishes and molluscs in Canada and further examine the nature of alien invasive species introductions affecting aquatic species at risk. Habitat loss and degradation is the predominant threat factor for Canadian freshwater fishes and molluscs that are listed as Extinct, Extirpated, Endangered and Threatened. Alien invasive species are the second most prevalent threat for fishes, affecting 26 of 41 listed species. Alien invasive species are a threat in most parts of Canada where listed fishes are found. Most (65%) of the alien invasive species affecting listed fishes are the result of intentional introductions related to sport fishing, and the majority of these introductions are unauthorized. Fifteen fishes and two plant species are cited as alien invasive species that impact listed fishes with brown bullhead (Ameiurus nebulosus) and pumpkinseed (Lepomis gibbosus) being the most prevalent. Alien species are a threat to 6 of 11 listed mollusc species. All six species are threatened by the alien zebra mussel (Dreissena polymorpha) in the Great Lakes basin. An erratum to this article is available at .     

Evaluating functional diversity conservation for freshwater fishes resulting from terrestrial protected areas

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Length-Weight Relationships for freshwater fishes from streams of the Atlantic Rainforest,State of Paraná, Brazil

This study reports the Length-Weight Relationships (LWR) for 10 freshwater fish species sampled in the Atlantic Rainforest, Southern Brazil. Sampling was conducted between 2016 and 2017, in nine streams, using electrofishing. Collected fishes were fixed in formalin, and thus some shrinking was unavoidable. The values of parameter b of the LWR (W = aL^b) ranged between 2.5 and 3.5. We report for the first time the LWR for seven species: Geophagus iporanguensis, Isbrueckerichthys duseni, Hypostomus interruptus, Kronichthys lacerta, Chasmocranu lopezi, Astyanax lacustris e Neoplecostomus ribeirensis. We highlight the importance of the LWR data in supporting further studies on fish stocks and environment in the Atlantic Rainforest, thereby contributing to the database needed to develop fisheries management and maintenance of ecosystem services.     

An assessment of fish species assemblages in rice fields in West Bengal,India: implications for management

Wetlands such as rice fields and associated canals are congenial habitats for different fishes and provide the foundation of rice‐fish culture. The selection of suitable fish species determines the success for this linkage of aquaculture and agriculture. An assessment of fish assemblages in selected rice fields and associated canals in West Bengal, India documented the candidate species for culture and conservation in rice fields. Indigenous minnow traps made of bamboo were employed in the rice fields and canals for a period of 3 months, to collect and record the fish abundance. A total of 531 fishes representing 19 different species were caught from the rice fields in 30 sampling efforts. From the canals, 13 different fish species totaling 676 fishes were collected in 80 sampling efforts. The fish collected per trap in the rice fields (mean 17.7 ± 1.97 SE) remained significantly different (t = 4.461, df = 112; P < 0.001) from those of the canals (mean 8.05 ± 1.09 SE). Diversity indices ranged between 1.91 and 2.01, with a 53% similarity between the rice fields and canals. Among the fish species collected, Badis badis, Colisa fasciatus and C. lalia exhibited high abundance; the two species Heteropneustes fossilis and Mystus vittatus established as threatened fish categories, showed low abundance. The fish species collected were important as food resources and the ornamental fish trade, and many of them bear potential in regulating mosquitoes in the rice fields. These fish assemblages in the rice fields and associated canals suggest a rice‐fish culture potential for integrating food and health.     

Do hotspots fall within protected areas? A Geographic Approach to Planning analysis of regional freshwater biodiversity

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Zoogeography and biodiversity of the freshwater fishes of Southeast Asia

The ichthyofauna of the freshwater system of Southeast Asia is extremely diverse. A recent estimate of about 1000 species is probably an understatement. More than 10 new species are being added to the list annually. The distribution pattern of the Southeast Asian freshwater fishes can be divided into five zoogeographic regions. The first one is the Salween basin in Burma, with fishes mainly of the Indian subcontinent origin such as Amblypharyngodon atkinsoni, Bangana almorae and Brachydanio jayarami. The second zoogeographic area is the Mekong, Chao Phraya and Mae Khlong drainages which harbour fishes typical of the mainland of Southeast Asia such as Acanthorhodeus deignani, Barbichthys nitidus and Cirrhinus siamensis. The Malay Peninsula is the third region whose species composition is heavily influenced by the Siamese (such as Homaloptera smithi, Tuberoschistura baenzigeri and Botia beauforti) and Indonesian (such as Botia hymenophysa, Luciocephalus pulcher and Parosphromenus deissneri) elements. The islands of Sumatra, Borneo and Java are the fourth zoogeographic area of fish distribution. These islands show a high degree of endemism, especially in fishes of the family Belontiidae. Finally, the freshwater system of the Philippines is the last zoogeographic region of Southeast Asia. The area is characterized by the presence of closely related species of the cyprinids especially in Lake Lanao. Currently, high diversity of these freshwater fishes is being threatened by land development, such as deforestation, road construction and land expansion for plantation. Recent studies in the Gombak River basin show the extermination of 41 per cent of native fish species from 1969 to 1990. This is probably due to the construction of highways, logging, as well as land clearing for agriculture.     

Impact of human activities on changes of ichthyofauna in Dongjin River of Korea in the past 30 years

Ichthyofauna and fish community were investigated at 17 representative stations of the Dongjin River drainage system from spring to fall in 2014. The survey resulted in a list of 53 species belonging to 14 families structured into 4 distinctive parts along the river: uppermost-stream, upper-stream, mid-stream, and lower-stream. Comparison of species lists with 30-year interval exhibited significant decreases in peripheral freshwater fishes, Acheilognathinae, endemic, and indigeneity species, but increases in exotic, epipelagic, and lentic species. Moreover, in the estuary of the Dongjin River drainage system, peripheral freshwater fish species were replaced by pure freshwater fish species due to the Saemangeum sea-wall project. In the upper region of the river, introduced eight alien species from Seomjin River via water diversion tunnels. In the mid-lower region, the construction of floodgates and numerous small weirs caused expansion of lentic water areas, facilitating the spread of problematic exotic species such as Micropterus salmoides, Lepomis macrochirus, and Carassius cuvieri. Also, water deterioration in this region resulted in an increase of tolerant species and a decrease of sensitive and endemic species. Our results suggest that a recovery strategy for a healthy ecosystem in the Dongjin River drainage system should reflect this compartmentalized cause and effect on the changes of icthyofauna.     

Phylogeographic structure in the threatened Yarra pygmy perch <Emphasis Type="Italic">Nannoperca obscura</Emphasis> (Teleostei: Percichthyidae) has major implications for declining populations

Molecular genetic information should be a pre-requisite when evaluating conservation priorities in highly structured species such as freshwater fishes. Nuclear (allozyme) and mitochondrial (cytochrome b) markers were used to investigate phylogeographic structure in the Yarra pygmy perch Nannoperca obscura (Klunzinger), a threatened freshwater fish endemic to mainland south-eastern Australia. Complementary patterns of strong, geographically defined sub-structure were observed including a major east–west divergence (at the Glenelg River), four diagnosable lineages, and statistically-significant differences between most populations. Accordingly, four Evolutionarily Significant Units (ESUs) are defined and multiple, drainage-scale Management Units (MUs) suggested. Since Nannoperca obscura is a relatively poor disperser with no apparent gene flow between most populations, any regional extirpation would see the irreversible loss of genetic diversity. This is problematic, as several populations, most notably a recently discovered ESU in the Murray-Darling Basin, are feared extirpated through a combination of anthropogenic threats and severe drought. The potential loss of unique evolutionarily components within N. obscura soon after their discovery highlights with some urgency, the need to define and protect conservation units in highly modified freshwater habitats.     

We need better understanding about functional diversity and vulnerability of tropical freshwater fishes

Here we extend a discussion initiated by Toussaint et al. (Sci Rep 6:22125, 2016) concerning the relationship between global patterns of freshwater fish functional diversity (FD) and its vulnerability to human impacts. Based on a set of morphological traits, they concluded that Neotropical freshwater fishes have highest FD, but low vulnerability given high levels of functional redundancy. This conclusion implies that conservation efforts for freshwater fishes should emphasize temperate regions. This perspective is risky, because Toussaint et al.’s study seriously underestimates the full scope of FD, including important ecosystem services provided by fishes in the tropics. We briefly discuss some additional and well-documented aspects of tropical freshwater fish FD and conclude that tropical fish FD is highly vulnerable.     

Toxicity and bioaccumulation of chromium in some freshwater fish

Chromium (Cr) is a common pollutant of freshwater bodies in India, and is frequently detected in high concentrations in edible fish. Bioassays were carried out in the laboratory to determine acute the toxicity and pattern of accumulation of Cr in three species of freshwater fish. The 96-h LC₅₀ value of Cr for Labeo bata, Puntius sarana, and Catla catla was found respectively as 7.33, 10.37, and 31.61 mg/L. Concentrations of Cr in water, sediments, and fish, during a period of 28 d of exposure to 0, 0.73, and 2.19 mg/L of Cr, varied with exposure period, concentration of Cr, presence of weed, and species of fish exposed. Polynomial regressions obtained by drawing polynomial curves revealed that the aquatic weed Eichhornia crassipes prevented gradual decrease of Cr concentrations in water, but reduced the accumulation of Cr in L. bata and Catla catla. However, the effect of the weed on Puntius sarana was not apparent. The pattern of Cr deposition on sediments was also inconsistent. To explain interactions between environment and fish in a very precise manner, polynomial and multiple regression curves were simultaneously used. When polynomial curves were replaced by multiple regression curves, it was revealed that the aquatic weed E. crassipes could reduce Cr accumulation in Puntius sarana also.     

Fish fauna, biogeography and conservation of freshwater fish in Poyang Lake Basin, China

A checklist of the fish of Poyang Lake Basin based on an extensive survey and literature review is presented. A total of 220 species and subspecies belonging to12 orders, 27 families and 100 genera, have been recorded. Of these, 131 species are endemic to China. Based on cluster analysis with presence-absence data, freshwater ecosystems in Jiangxi Province are divided into two regions, the Xunwushui River region and the region of Poyang Lake. The Xunwushui River flows into the Pearl River, whereas the region of Poyang Lake flows into the Yangtze River. The fish fauna and evolution of the fish fauna in Poyang Lake Basin owes much to geological events and belongs to the Oriental Region, South-east Asiatic sub-region and East China area. Anthropogenic activities including habitat alteration, overfishing, pollution and soil erosion have severely reduced the fish biodiversity in Poyang Lake Basin. River modifications (i.e. dam construction and sand excavation) and heavy metal pollution are the most significant threats to fish diversity and ecosystem functioning in the majority of the river systems in the province. To protect fish diversity and fisheries more effectively in Poyang Lake Basin, law enforcement should be strengthened, and the following measures could be introduced: restocking economically important fish species; establishing fish sanctuaries and freshwater protected areas, ordering a close season and developing sustainable aquaculture.     

The Asian Fish Tapeworm Bothriocephalus acheilognathi: a Potential Threat to Native Freshwater Fish Species in Mexico

Introduction of the parasite Bothriocephalus acheilognathi Yamaguti, 1934 with the herbivorous carp Ctenopharyngodon idellus, and other cyprinids, has been documented in almost every continent, except Antarctica. This study presents the current geographical distribution of this cestode in the freshwater fish of Mexico, highlighting infections in autochthonous and endemic species. It compiles existing information and presents original data. B. acheilognathi is widely dispersed among the freshwater fish of Mexico, being recorded to date in 49 fish species from 26 genera, 7 families and 5 orders. B. acheilognathi is reported from Mexico for the first time in Dionda ipni, Notropis celayensis, Yuriria alta, Gambusia vittata, Poecilia butleri, P. mexicana, Poeciliopsis baenschi, Poeciliopsis sp., Cichlasoma cyanoguttatum and C. labridens. The new hosts identified in this study bring the total number of known host species to 102 in 14 families and 7 orders of freshwater fishes around the world. Given its wide distribution among Mexican freshwater fish species, the abundance of the parasite and its high pathogenicity, parasitological data for B. acheilognathi should be considered as an important factor in native fish conservation policies. Biological changes in the freshwater habitats in Mexico caused by the introduction of exotic fish species and their parasites are virtually ubiquitous and extremely difficult to eradicate once established. As such, they should be considered as one of the most serious threats to native fish conservation.