On the freshwater fish fauna of Krishna River, Sangli District, Maharashtra, India

Freshwater fish fauna of Krishna River, Sangli district was studied from 2013 to 2017. A total of 73 species belonging to 10 orders, 22 families, and 49 genera were recorded, of which, 29 species are endemic to the Western Ghats and 11 species endemic to the Krishna River system. Labeo kontius, an endemic barb of the Cauvery River System was recorded for the first time from the Krishna River, Maharashtra. As per the IUCN Red List of Threatened Species, 54 species are assessed as ‘Least Concern’, four species as ‘Near Threatened’, three species as ‘Vulnerable’, five as ‘Endangered’, and two as ‘Data Deficient’. The conservation status of two species has not yet been assessed. Fish fauna of the Krishna River within the study area is threatened as a result of alien species, and several anthropogenic stressors such as pollution from industrial as well as agricultural sources, human settlements, and overfishing. Since, this small study area harbours 28 endemic and eight threatened species, their conservation should be given high priority.


OPEN ACCESS
The Western Ghats of India is global biodiversity hotspot (Myers et al. 2000), known for its high level of endemism of taxonomic groups such as amphibians and freshwater fish. Around 320 species belonging to 11 orders, 35 families, and 112 genera are known from this region (Dahanukar & Raghavan 2013) and this number is certain to increase given the high number of species being discovered on a yearly basis. Krishna is one of the major perennial rivers of the northern Western Ghats. The river originates at Mahabaleshwar (17.988 0 N; 73.637 0 E), Satara District, Maharashtra, and traverses a distance of 290 km through Satara, Sangli, and Kolhapur districts in Maharashtra, thereafter flowing through the states of Karnataka and Telangana before emptying into the Bay of Bengal at Hamasaladeevi in Andhra Pradesh.
Earliest studies on the fish fauna of Deccan was carried out by Sykes (1839). Specific studies on the fish fauna of the Krishna River (in addition to the Godavari) were carried out by David (1963), but no separate 'riverwise' locations for the species collected, were provided. A major study on the fish fauna of Krishna River was also carried out by Jayaram (1995), but no separate list of fishes collected specifically from the tributaries in Sangli District was provided.
Previous studies on the fish fauna of Krishna River has largely focused on the tributaries in Satara District. Annandale (1919) reported 18 species from the Yenna River at Medha, followed by Silas (1953) who studied the fish fauna of Mahabaleshwar and Wai and recorded 14 species. Arunachalam et al. (2002) recorded 14 species from Dhom reservoir, and subsequently Jadhav et al. (2011) reported 58 species from the Koyna tributary. More recently, Kharat et al. (2012) provided an updated checklist of the fish fauna of Krishna River at Wai and Dhom reservoir, and reported the presence of 51 species. The only published work on the freshwater fishes of the Krishna River in Sangli District is by Kumbar & Lad (2014) who recorded 13 species of catfishes. In the present paper, we provide a comprehensive checklist of the freshwater fishes of the Krishna River flowing through Sangli district in Maharashtra and identify possible threats so as build baseline data for future conservation action.   (Figure 1), with the help of local fishers using different mesh-sized gill nets and cast nets. Alternatively, fish samples were also procured from local fish markets.

Results
We recorded a total 73 species of freshwater fish belonging to 10 orders, 22 families and 49 genera from the Krishna River in Sangli district (Table 1). Order Cypriniformes dominated with 42 species, followed by Siluriformes (18 species), Anabantiformes (three species), Synbranchiformes, Perciformes, & Beloniformes (two species each), and Cyprinodontiformes, Gobiiformes, Osteoglossiformes, & Cichliformes (one species each). Representative species of fish collected from Krishna River are shown in (Images 1, 2, 3 & 4). As per the IUCN Red List of Threatened Species, 54 species are assessed as 'Least Concern', four species as 'Near Threatened', three species as 'Vulnerable', five as 'Endangered', two as 'Data Deficient', and the conservation status of two species has not yet been assessed. Of the 73 species, 29 are endemic to the Western Ghats, and 11 are endemic to the Krishna River System (Table 1). Microlevel distribution of species along the upstream-downstream gradient showed that 56 species occurred in upper reaches, 28 species in middle stream, and 37 species in downstream respectively ( Figure 1). Of the total fish collected, 15 species were found to be common, six abundant, 28 moderate and 24 rare.
Fish fauna of Krishna River is severely threatened by pollution from organic wastes particularly around the towns of Sangli and Miraj as well as from pollution due to agricultural runoff and sewage. Recently, sand mining has also increased significantly along the stretch of the river near Bahe and Borgaon, resulting in the loss of available habitats to the fish fauna of these areas. Similarly, overfishing, indiscriminate use of poison to collect fish in large numbers and using fine-meshed gill-nets, is a specific threat to species of the genera Bangana, Tor, Hypselobarbus, Labeo, Cirrhinus, Opsarius, Salmostoma, Botia, Mystus, Cirrhinus, and Puntius. We also recorded seven non-native species-four transplanted: Cirrhinus mrigala, Labeo rohita, Labeo catla, Labeo calbasu in all sites and three alien invasive species: Oreochromis mossambicus, Cyprinus carpio and Clarias gariepinus at Sangli and Miraj. Studies in their entirety of Krishna River by Jayaram (1995) have recorded 10 invasive alien species, but interestingly Jadhav et al. (2011) could not record any alien species from Koyna tributary. However, Dahanukar et al. (2012) recoded seven introduced species from Indrayani River near Pune, and four species from Hiranyekeshi River by Kumkar et al. (2017).

Discussion
Krishna River harbours a number of endemic and threatened species. We collected Glyptothorax cf. poonaensis from Bahe near Islampur in moderate numbers. These specimens resemble G. poonaensis (Hora 1938), but differs considerably with the description provided in Dahanukar et al. (2011). It is therefore possible that this species might comprise a 'complex'. The population of Endangered and endemic Bangana nukta is declining drastically in the study area as per the local knowledge of fishers. Pollution, overfishing and the competition created by transplanted carps such as  Labeo potail, a species that has been assessed as 'Endangered' due to population decline of 50-60 % in the last 10 years due to organic and inorganic pollution, exploitation and competition created by transplanted carps (Dahanukar 2011) was collected near Palus and Sangli. However, their numbers are declining rapidly due to pollution from domestic organic waste and effluents released heavily from industries situated on the riverbank. Another Krishna River endemic and threatened species, Botia striata (locally called 'waghmasa') (Image 3-22) was recorded from Bahe, Borgaon and Islampur. At Bahe and Borgaon, indiscriminate collection of this species by aquarium traders in the summer months is a major threat to the species. The species is however relatively abundant in the study area, and also in Koyna River (Jadhav et al. 2011). Gagata itchkeea (Image 3-25) a species recorded previously from the Krishna River system (Kalwar & Kelkar 1956;Jayaram 1995;Kharat et al. 2003;Wagh & Ghate 2003;Chandanshive et al. 2007) was collected from Bahe in very low numbers. Other important endemic species such as Garra bicornuta, Parapsilorhynchus discophorus, Pachypterus khavalchor were also collected from various sampling sites.
We recorded Labeo kontius (Image 1) for the first time from the Krishna River system in, Maharashtra State, through samples from Miraj, thus extending its range to the northern part of the Western Ghats. Labeo kontius was described by Jerdon (1849) from Cauvery River and its tributaries. Currently, the species is also known to occur in the Bhavani and Moyar rivers and their tributaries (Rajan 1955;Manimekalan 1998), as well as in the main stretch of the Cauvery River (Jayaram et al. 1982;Jayaram & Dhas 2000).
Krishna River harbours a rich diversity of endemic and threatened fishes of Western Ghats. However, this fauna is threatened due to overfishing, introduced species, sand mining and organic and inorganic pollution. If the present anthropogenic impact continues, this might lead to a drastic decline of habitats and populations of fish species available in this region. It is therefore essential to declare some stretch of rivers as aquatic sanctuaries, particularly near Bahe and Miraj for protection and preservation of endemic and threatened species and mitigation of anthropogenic stress. www.threatenedtaxa.org The Journal of Threatened Taxa (JoTT) is dedicated to building evidence for conservation globally by publishing peer-reviewed articles online every month at a reasonably rapid rate at www.threatenedtaxa.org. All articles published in JoTT are registered under Creative Commons Attribution 4.0 International License unless otherwise mentioned. JoTT allows allows unrestricted use, reproduction, and distribution of articles in any medium by providing adequate credit to the author(s) and the source of publication.