Within the freshwater fish order Cypriniformes, loaches form a monophyletic lineage comprising nine families with more than 1400 species. Secondary sexual dimorphism is widespread among loach families, most notably in the form of enlarged pectoral fins and tubercles or other ossified structures on the pectoral fin in adult males. To date, the family Botiidae, phylogenetically sister to all other loach families, was reported to lack such sexually dimorphic structures, leading to the hypothesis that the common ancestor of loaches did not exhibit sexual dimorphism. Here, we report the presence of sexual dimorphism in eight species of Botiidae: Leptobotia bellacauda, L. guilinensis, L. microphthalma, L. taeniops, L. tchangi, Parabotia fasciatus, Sinibotia pulchra, and S. robusta. In all species, adult males possess longer pectoral fins than females. Additionally, males of L. guilinensis and L. tchangi exhibit larger pelvic fins, while males of L. microphthalma have larger anal fins. In L. bellacauda, L. microphthalma, and L. tchangi, portions of the dorsal surface of the pectoral fin bear rows of tubercles. The three genera displaying sexual dimorphism belong to two different subfamilies, demonstrating that sexual dimorphism is widespread across Botiidae and not restricted to a single genus or subfamily. Our results show that sexual dimorphism is present in the most basal family of loaches, suggesting that it represents a synapomorphy of loach fishes.

The present study “Fish Diversity of Champabati River in Bongaigaon district with special reference to ornamental fish” was carried out with an objective to investigate the fish diversity especially ornamental fish diversity in the river Champabati of the district Bongaigaon, Assam. To facilitate the research objective, the tributary was divided into three different stations at regular distance. Field surveys were conducted from May, 2022 to June, 2023. For catching the fishes mainly cast net, floating gill net, boat seine, rod and hook line, etc were used. A total of 453 Number of fishes were collected, among which 218 number of fish were form Station I, 155 number of fishes were from station II and 80 number of fishes were from Station III. Altogether 36 Ornamental Fish species belonging to 09 orders and 19 families were observed in the study area. Among the total fish species, Cyprinidae family constitutes the largest group consisting of 13 species, followed by family Channidae consisting 03 species. The highest frequency occurrence of order Cypriniformes was 41.22% and of family Cyprinidae was 36.11%. The most common fish species found in all station were Puntius sophore, Glossogobius guiris, Aspidoparia morar, Trichogaster fasciata, Puntius titco, Labeo bata, Amblypharyngodon mola, Cirrhinus reba etc.

Ornamental fish fauna possess attractive colouration in nature and are used primarily for aesthetic purposes in aquaria and small ponds. This investigation from March 2023 to December 2023 for three seasons focused on the diversity of indigenous ornamental fish species in Bardia District, Lumbini Province of Nepal. Twelve specific sampling sites were thoroughly surveyed for the presence of locally inhabiting ornamental fish species during the study period. A total of 32 indigenous ornamental fish species, under 20 genera, 16 families, and 6 orders, were identified. The dominant species number belongs to the order Cypriniformes, which is followed by Siluriformes and Anabantiformes. This survey indicated that all the ornamental fish species recorded are indigenous to the Bardia District. The conservation status of the reported ornamental fish, according to the IUCN, indicates that one species, Clarias magur, is classified as Endangered (EN). Additionally, two species are categorised as Near Threatened (NT), twenty-eight species are listed as Least Concern (LC), and one species has not yet been evaluated (NE). Of the available data on indigenous ornamental fish species, Danio spp., Botia spp., Chanda spp., Trichogaster spp., Esomus danrica, Nandus nandus and Xenentodon cancila are overlooked in reference to trade and conservation, despite their significant aesthetic value and aquarium trade potential. Habitat management, domestication, and promoting markets for native ornamental fish species are crucial to reduce the growing dependence on imported fish in Nepal.

This study was conducted in Rapti River in Makawanpur located between latitudes 27° 21’ 23" N to 27° 47’ 00" N and longitudes 84° 08’ 43"E to 85° 11’ 57" E. It was carried out throughout Bhainse to Lothar, border of Makawanpur and Chitwan with a range of about 40 km. The objective of this study was to discover the fish diversity in Rapti River, Makawanpur and to determine the Shannon-Weiner’s and Margalef’s richness diversity indices. A total of 4 stations were set on the basis of human settlement along Bhainse, Hetauda, Manahari and Lothar. The field work was conducted from January 2025 to August 2025 to cover winter and summer seasons. The fishes were collected by employing local fisherman by using locally prepared fishing gears. A total of 40 fish species were collected belonging to 7 orders, 10 families and 25 genera. The order Cypriniformes was the most dominant, comprising 30 species and accounting for 75% of the total collection. It was followed by Siluriformes with 4 species (10%), Anabantiformes with 3 species (7.5%) and Clupeiformes, Synbranchiformes and Beloniformes, each represented by 1 species (2.5%). The Barilius bendilisis comprises the highest frequency of 20.14% of total catch followed by Garra gotyla 8.14%, Puntius ticto 8% and Schistura beazvani 7.71%. The highest Shannon-Weiner’s index was recorded at Manahari (2.47) and lowest at Bhainse (1.97). The high Margalef’s species richness was recorded at Lothar (4.21) and low at Bhainse (1.85). Manahari has the highest diversity and Lothar has the highest richness. This indicate that Lothar has many species but their distribution is slightly less even than in Manahari where the species richness is high. The present study benefit researchers and locals for the conservation of valuable aquatic fish fauna enhancing biodiversity richness.

The present study investigated the species composition and spatial distribution of fish assemblages in the upper reaches of the Tien River in Dong Thap province. Samples were systematically collected at four fixed sites within the headwater basin from March to August 2025. A total of 86 species, representing 59 genera, 36 families, and 14 orders, was recorded. Among these, members of the order Cypriniformes exhibited the greatest species richness (25 species), followed closely by Siluriformes (22 species). Species assemblages displayed marked seasonal shifts, with composition differing between the rainy season and the preceding dry period. Importantly, the survey documented a number of threatened taxa. Several rare species appear on the IUCN Red List (2025) and the Vietnam Red Data Book (2024), underscoring the conservation value of this riverine system. Furthermore, analysis of encounter rates revealed that most species had low to very low frequencies of occurrence, pointing to either naturally sparse populations or anthropogenically induced declines. Overall, these findings provide a baseline for biodiversity monitoring and resource management in the upper Tien River. They highlight the need for integrated conservation strategies that account for seasonal dynamics and protect vulnerable taxa. Continued monitoring is therefore recommended to detect long‐term trends and to inform adaptive management in the face of ongoing environmental change.

Abstract The aim of this study is to describe the biodiversity and current status of ichthyofauna in the Lesser Zab River. Through the examination of more than 1,500 samples collected from various river stations between May and August 2014 and June and August 2016, 35 fish species belonging to six families have been identified. The fish identified belong to the orders Cypriniformes, Siluriformes, and Synbranchiformes, which include Cyprinidae, Balitoridae, Sisoridae, and Mastasembelidae. Both meristic and morphological analyses were conducted on the specimens. Some of these species are reported for the first time in this part of the Zab River. Additionally, the study mentions the effects of anthropogenic and climate changes on fish biodiversity in this basin.

The present study focused on evaluating the species richness, distribution, conservation status, and economic value of fish in these Umiam River, Umngot River, and Kynshi rivers based on a field survey of six months duration between October 2024 and March 2025. Using a combination of traditional and modern fishing techniques, a total of 67 fish species were recorded, spanning 45 genera, 22 families, and 8 taxonomic orders. Among these, the order Cypriniformes was the most species-rich, with the family Cyprinidae alone accounting for over half of all identified species. The Umngot river, with its clear water and minimal anthropogenic disturbance, had the maximum species diversity, while the Kynshi river showed lower diversity, which could be related to mining-induced pollution. A total of 67 species belonging to 45 genera and 22 families were recorded. Notably, over 10% of species were found to be under various IUCN threat categories. Interestingly, a number of high-value ornamental species were reported, which is an indication of both the natural richness and economic value of the region's ichthyofauna. The research emphasizes the twofold importance of freshwater fish as indicators of ecosystem health and as important livelihood resources. It recommends an integrated conservation strategy that involves community participation, responsible fishing practices, and the protection of natural habitats to ensure the continued health of fish populations and their surrounding ecosystems.

Vertebrates have undergone two rounds of whole‐genome duplication (WGD), termed 1R and 2R, with a third, teleost‐specific duplication (TSGD or 3R) occurring in ray‐finned fishes. In the order Cypriniformes, additional lineage‐specific WGDs have further contributed to species diversification. While polyploidy is well characterized in species like common carp and goldfish, other polyploid taxa—particularly loaches—remain understudied. Here, high‐quality, chromosome‐level genome assemblies are presented for two loach species: Sinibotia superciliaris (Golden Chinese Loach) and Parabotia fasciatus (Yichang Sand Loach). By integrating these genomes into a comparative framework with 20 other cypriniform species, key phylogenetic relationships are reconstructed, and introduce a novel subgenome partitioning method (M3). Unlike previous approaches, M3 uses differential sequence divergence to accurately and rapidly assign subgenomes, completing partitioning within minutes and outperforming existing tools. Applying M3, a markedly reduced subgenome is uncovered in the Golden Chinese Loach, with lineage‐specific molecular changes in several candidate genes, suggesting potential adaptive significance. This study offers a comprehensive view of polyploidy and subgenome evolution in loaches, highlighting the genomic complexity shaped by repeated WGDs in Cypriniformes and providing valuable resources for future research on vertebrate genome evolution and adaptation.

Abstract Organisms utilizing lower trophic levels consume nutrient-poor foods with little energy and must maximize nutrient extraction during digestion. In fishes, there is a strong inverse relationship between trophic level and intestine length and a positive relationship between body length and intestine length. Adaptation to lower trophic levels and concomitant increases in intestine length may influence either the size of the abdominal cavity region or overall body size, as the fish must accommodate longer intestines. This study evaluates these two alternative adaptive pathways in 122 North American species from the order Cypriniformes. We used traditional dissection and microcomputed tomography scans to measure intestine length and abdominal cavity volume. We used a suite of phylogenetic comparative methods to determine whether diet influenced intestine length, body size, and abdominal cavity volume. Our results show that the herbivore–detritivore trophic group has significantly longer intestines than at least one other trophic group and is evolving towards a larger optimal intestine length than all other trophic groups. Furthermore, we see a positive, significant relationship between abdominal cavity volume and body size. These results support the inverse trophic position–body length pattern seen in the group and further elucidate the evolutionary limitations based on body shape covariation in predicting diversification in freshwater fishes.

A comprehensive fish diversity study in the Rupnarayan River in West Bengal, India, were undertaken for two years, once every month at four separate study locations. Recorded a total of 109 fish species, which were ultimately divided into 82 genera, 44 families, and 19 orders. Seventy-one of the total number of fish species were designated as being the first to be documented from the Rupnarayan’s water. The order Cypriniformes has the highest composition (18.26%), followed by the Siluriformes (13.80%), Clupeiformes (13.42%), and so on. Cyprinidae represented 17.02% of the total, followed by Mugilidae (9.40%), Engraulidae (7.90%), and so forth. In the winter, Station II had the greatest Simpson's index of diversity (0.983), whereas in the summer, Station III had the lowest (0.961). Sorensen's findings reveal strong predicted similarities between stations I - II (0.84) and II - III (0.76), moderate similarities between stations III - IV (0.63), and a dissimilarity between stations I - IV (0.26). The current study is an up-to-date documentation of the finfish faunal variety and spatial distribution along the entire length of the Rupnarayan River will certainly be a helpful baseline data for future researchers and fishery planners.

Freshwater fishes in Malaysia are relatively diverse with species of primary freshwater fishes. The total species richness of freshwater fishes of Malaysia remains unknown, this is due to many inland water bodies that have not been sampled. This study was conducted to ascertain the abundance of the freshwater fish at selected lakes in Maran, Pahang. The aim of this study to determine freshwater fish diversity and the relationship with water characteristics. All captured fish were measured, weighed and identified. Sample of water were collected from each lake. Water was analysed for pH, temperature, turbidity, total dissolved solids, dissolved oxygen and biological oxygen demand. A total of 107 individuals of fish compromising 8 species and 7 families were recorded. Trichopodus trichopterus was the most abundant species with total of 44 individuals which belonging to Order Anabantiformes and the least species with total of one individual captured which belonging to Order Cypriniformes, which is Puntigrus partipentazona. The highest diversity of fish was recorded at Lake 3 with Shannon Wiener Diversity Index H’= 1.428 and the lowest was at Lake 1 with H’= 0.968. The highest evenness index of fish species was detected at Lake 3 with Pielou’s Evenness J’= 0.797 and the lowest was at Lake 1 with J’= 0.698. Meanwhile, the most diverse species was found at Lake 3. Canonical Correspondence Analysis (CCA) ordination diagram of fish communities and selected water properties showed that Notopterus notopterus, Pristolepis fasciata and Puntigrus partipentazona were associated with the environment variables such as total dissolved solids (TDS) and turbidity while Oreochromis mossambicus and Oxyeleotris marmorata were not associated with any of the variables.and water salinity.

Dam construction alters river hydrology, influencing the temporal and spatial heterogeneity of fish communities. This study utilized environmental DNA (eDNA) sequencing to analyze seasonal variations in fish communities in the Duliu River, Guizhou Province, and to assess the impact of hydrological regulation on biodiversity. High-throughput sequencing revealed that sequence reads were significantly higher in the dry season than in the wet season (P < 0.05), while operational taxonomic unit (OTU) richness was greater in the wet season. A total of 69 fish species (6 orders, 18 families) were detected in the dry season, with only 23 species matching historical records. eDNA sequencing identified an additional 46 species, primarily from the order Cypriniformes. In the wet season, 82 species (7 orders, 17 families) were recorded, including 44 species not found in historical data. Cypriniformes dominated in both seasons, comprising 94% of the community in the dry season and 82% in the wet season. Spatial heterogeneity analysis using principal coordinates analysis (PCoA) indicated significant differences among river sections (PC1 = 65.2% in the dry season; 83.65% in the wet season). Beta diversity analysis (NMDS) confirmed significant temporal and spatial variation in fish communities (P < 0.05). This study highlights the ecological impact of dam construction on fish communities and underscores the need for conservation strategies to protect biodiversity in regulated mountain rivers.

The diversity and distribution of fishes were studied in the Chinnar and Thenar rivers of the Cauvery River basin of Anamalai Hills. A total of 14 sampling sites were randomly selected in this region, and fish sampling was carried out from April 2017 to May 2018. The high species diversity was recorded in downstream site 11, Thenar River (H’ = 3.14), and low diversity was observed in upstream site 3, Chinnar River (H’ = 1.64). Thirty-seven species of primary freshwater fishes belonging to four orders, 11 families, and 21 genera were recorded. The order Cypriniformes, with 26 species, dominate the fish assemblages (70.27%), followed by Perciformes with six species (16.21%), Siluriformes with four species (10.81%), and Synbranchiformes with one species (2.70%), respectively. Among the Cyprinids, Devario aequipinnatus, Barilius getensis, and Garra mullya had the highest local dominance (32% each) in this river’s cape. The only one exotic species, Oreochromis mossambicus, was recorded at downstream sites of Amaravathi River. Among the recorded species, about 43% of fish species are endemic to the Western Ghats, seven species are listed as threatened, five as endangered, and two are vulnerable, according to the IUCN Red List.

The fish fauna of Yerla River, Sangli district was studied between 2021 to 2024. It is aimed at making a comprehensive checklist and to find out real anthropogenic threats to the fish fauna of Yerla River. A total of twelve species belonging to two orders, five families and eight genera were recorded. Order Cypriniformes were the most dominant one and represents eight species followed by Siluriformes with four species. Among these, three species are endemic to the Western Ghats and one species is endemic to the Krishna River System. As per IUCN’s Red list of Threatened Species, nine species assessed as least concern; two species as endangered and one species as vulnerable. The fish fauna of the river is threatened due to exotic species like Pterygoplichthys pardalis and Pangasianodon hypophthalmus of various sites of Yerla River and some anthropogenic activities like releasing of agricultural effluents, domestic organic wastes and non-degradable plastic materials owing to tourism activities. Since, this small study area hosts four endemic and three threatened species. Therefore, Yerla River will be the most suitable habitat for conservation of endemic and threatened species.

The present study investigates the ichthyofaunal diversity of Lakshmipuram Lake in Anakapalli District of Andhra Pradesh state of India from January 2024 to December 2024, a vital freshwater body supporting ecological balance and local livelihoods. A total of 47 fish species were identified at different sites. Freshly collected fishes were carefully cleansed and photographed. They were preserved in 9-10% formalin solution. Fish species were identified using classical taxonomical observations. Among the identified 12 orders, the order Cypriniformes was dominant with 18 species which contributed to 37% followed by Siluriformes 10 (21%), Perciformes 3 (4%), Channiformes, Cichliformes, Anguilliformes each 3 (6%), Beloiniformes, Synbranchiformes each 2 (4%), while Cyprinodontiformes, Gobiiformies, Osteoglossiformes, Anabantiformes each 1 (2%). The population status of 11 species were abundant which contributed to 23% whereas 25 species were common contributing to 53%, 4 species were moderate by contributing to 8%, and the least percent of species i.e., 7 were represented as rare which contributed to only 14%. According to IUCN 2024, 36 species contributed around 77% are least concern (LC), 8 species contributed about 16% are near threatened (NT), about 2 species contributed to 4% are not evaluated (NE), and 1 species of 2% are data deficient (DD). As per the present study, the Lake is found good potential with variety of freshwater fish fauna.

An analysis of fish diversity in the mountain rivers and tributaries of the Araks (Aras) River drainage basin – including the Turkish, Armenian, Iranian, and Azerbaijan sectors – revealed a total of 27 species, representing six families and 16 genera. In the mountain rivers of southeastern Armenia, we identified eight species belonging to four families (Cyprinidae, Leuciscidae, Nemacheilidae, and Salmonidae) and two orders (Cypriniformes and Salmoniformes). The native species Salmo caspius, Barbus cyri, Alburnoides eichwaldii, and Capoeta capoeta are consistently present and dominate the ichthyofauna of all mountain rivers within the Armenian section of the Araks River basin. In addition, the fish community includes non-native species such as Carassius gibelio, Pseudorasbora parva, and Oncorhynchus mykiss. Among these, C. gibelio and P. parva accounted for 14.8% of fish occurrences, while O. mykiss was recorded only rarely. Oxynoemacheilus cf. brandtii was documented for the first time in the Aragilijur and Ayriget rivers, while Oxynoemacheilus bergianus was found in the Vachagan River; both species coexist within the same river basin. Overall, our study indicates a relatively low ichthyofaunal diversity in the small mountain rivers of Armenia when compared to the richer fish assemblages of the main Araks River.

Burhi Gandak River is a left-bank tributary of River Ganga and a major riverine ecosystem in North Bihar. The river is home to different freshwater fish species, gastropods, bivalves, and other aquatic animals. The fish diversity and Water quality parameters data were collected in six sampling locations from the period of August 2020 to June 2021. The present study examined fish diversity and their relationship with water quality parameters. The study revealed that Burhi Gandak River is the home of 71 fish species (67 indigenous and 4 exotic species). Identified species belong to 28 families, 10 orders, and 52 genera. The Order Cypriniformes contributes (45%) and 19 fish species belonging to the family Cyprinidae constitute the major diversity of the river. The maximum number of species was documented from location S4 (Pusa) and minimum from S2 (Muzaffarpur) respectively. The four types of diversity indices i.e., Shannon–Wiener (2.886 to 3.206), Simpson’s (0.9235 to 0.9449), Margalef’s richness (4.768 to 6.82) and Pielou’s evenness (0.4935 to 0.5708) were also assessed, and values of diversity indices vary from each location. Canonical correspondence analysis (CCA) indicates that pH, free CO2, water temperature, and dissolved oxygen were the key water quality parameters in the Burhi Gandak River. Four exotic species namely Ctenopharyngodon idella, Barbonymus gonionotus, Carassius carassius and Cyprinus carpio were recorded. According to the IUCN RedList, out of 71 fish species, 4 Near Threatened (NT), 1 Vulnerable (VU) and 66 Least Concern (LC).

The present study was carried out to know the Ichthyofaunal diversity and their conservation status in the river Kuwano, flowing through Balrampur district of Uttar Pradesh. The systematic survey of five sampling sites of the river was conducted once in a month for a period of one year from February 2024 to January 2025. The result of this study revealed the occurrence of 58 species belonging to 36 genera, 20 families and 8 orders. The order Cypriniformes was found as dominated order with 24 species (41.38%) followed by Siluriformes 16 species (27.59%), Perciformes 7 species (12.07%), Ophiocephaliformes 4 species (6.90%), Mastacembeliformes 3 species (5.17%), Osteoglossiformes 2 species (3.45%), Clupeiformes 1 species (1.72%) and Beloniformes with 1species (1.72%). According to IUCN red list most of the species (51) are under least concern (LC), while 5 species including Hypophthalmichthys molitrix, Notopterus chitala, Ompak bimaculatus, Ompak pabda and Ailia coila are in near threatened (NT) category and the remaining 2 species Wallago attu and Bagarius bagarius are reported as vulnerable (VU) category. The river Kuwano and its fauna are under severe ecological degradation due to anthropogenic activities, overfishing, illegal fishing approaches, aquatic pollution, siltation, introduction of exotic species of fishes and alien plant species. Thus, there is an urgent need to taking up steps to maintain this valuable river and to conserve the aquatic fauna and flora. The present study will provide base line data and may contribute as skeletal information for future studies of this river ecosystem. Author strongly recommends practical conservation action plan to prevent the Ichthyofauna from extinction.

Dikhu River constitutes one of the major perennial rivers of Nagaland and due to its pristine beauty aids as a tourism spot. From the present study, ichthyofaunal diversity accounted for a total of 28 fish species belonging to 6 orders, 13 families, and 3 subfamilies. From the investigation, order Cypriniformes (67.9%) was found to be the most dominant, followed by Siluriformes (14.3%) and Anabantiformes (7.1%) while order Beloniformes, Synbranchiformes and Anguilliformes was found to be the least common with 10.7% in total. The IUCN red list of threatened species shows 71.4% are Least Concern, 7.1% Near Threatened, 3.6% Vulnerable, 3.6% Endangered, 10.7% Not Accessed and 3.6% Data Deficient. IUCN population status data shows that 57.1% are unknown, 10.7% stable, 10.7% not accessed, and 21.4% with decreasing population trends. Diversity indices (Shannon, Simpson, and Evenness) indices ranged 2.497–2.912, 0.892–0.936, and 0.820–0.908, respectively. Relative abundance determinations ranged from a high of 15.55% for Devario aequipinnatus to the lowest values for Tariqilabeo latius and Botia rostrata at 0.08%. Anthropogenic pressure on the Dikhu River has resulted in habitat modification and fragmentation, posing a hazard to fish diversity. Fish abundance was found to be highest in the post-monsoon season and lowest in winter. These findings are significant for academic purposes and support conservation strategies for local fish resources.

Exploring the intricate dynamics of aquatic ecosystems present study investigates the spatio-temporal variations in the ecological parameters of the fish community within the Vaishav stream, Kashmir Himalayas. Monthly field investigations were conducted at three distinct sites (SI, SII & SIII) throughout the four seasons (winter, spring, summer, autumn) from November 2019 to October 2020. The findings encompass a total of 630 specimens belonging to 11 fish species, three orders Cypriniformes, Siluriforms and Salmoniformes and four families including Cyprinidae, Nemachelidae, Siluridae and Salmonidae were reported from the study sites. Among collected specimens, Cypriniformes were dominant with nine species followed by order Siluriformes and Salmoniformes with one species each. Out of eleven fish species, six fish species belongs to family Cyprinidae, three to Nemachelidae, one to Siluridae and Salmonidae each. The analysis, employing non-metric multidimensional scaling (NMDS), Principal component analysis (PCA), Analysis of similarity (ANOSIM) and Per-mutational multivariate analysis of variance (PERMANOVA) on fish abundance data highlighted significant differences among the various sites but not across seasons. The results unveil a diverse occurrence and distribution pattern of fishes from upstream to downstream. Furthermore, diversity metrics confirm higher diversity index values downstream, indicating a more conducive environment for fish survival. Jaccard's index reveals greater similarity in fish fauna between site-II and site-III than site-I and site-III in terms of overlap of fish species composition. The study concludes that anthropogenic activities in the stream catchment area have led to a reduction in fish diversity and abundance, with landscape features significantly influencing fish abundance in this unique Himalayan ecosystem.