Ichthyofaunal diversity in the upper-catchment of Kabini River in Wayanad part of Western Ghats , India

We present here a detailed account of the diversity, distribution, threats, and conservation of freshwater fishes in the uppercatchment of the Kabini River in the Wayanad part of the Western Ghats Biodiversity Hotspot. A total of 136 fish species belonging to 13 orders, 29 families, and 69 genera were recorded. Order Cypriniformes dominated with five families, 36 genera, and 84 species, and Cyprinidae was the dominant family represented by 51 species within 21 genera. The true diversity of ichthyofauna in this catchment, is still unclear and requires further exploration and taxonomic studies. At least 44 species recorded during the study are endemic to the Western Ghats, of which 16 are endemic to the Cauvery River System and two species endemic to the Kabini Catchment. A total of 20 non-native fish species were recorded from the study area, of which six species were inter-basin (within India) transplants and 14 species were exotic. Among the native species with confirmed identity, four are Critically Endangered (CR) and nine Endangered (EN) as per the IUCN Red List of Threatened Species. As a part of the study, we also extend the distribution ranges of Opsarius malabaricus, Laubuka trevori, Opsarius bendelisis, Puntius cauveriensis, Oreichthys coorgensis, Mesonoemacheilus pambarensis, Hypselobarbus curmuca, and Pseudosphromenus cupanus to the Kabini Catchment. The presence of four species, which were earlier considered to be endemic to the west flowing rivers of the Western Ghats, viz, Laubuka fasciata, Hypselobarbus kurali, Sahyadria denisonii, and Puntius mahecola, in an east flowing stream is reported and discussed. Deforestation and removal of riparian vegetation, pollution, stream channel modification, sand mining, destructive fishing practices, dams and other impoundments, monsoon fishing, and non-native species are the major threats to freshwater fishes in the region. Strategies for the conservation of aquatic ecosystems in the Kabini Catchment are discussed.


INTRODUCTION
The Western Ghats of India, a global biodiversity hotspot (together with Sri Lanka) is also the principal watershed of peninsular India (Myers et al. 2000). Rivers and streams of the Western Ghats are exceptionally biodiverse with high levels of endemism (Kottelat & Whitten 1996;Dahanukar et al. 2011). Much of these critical ecosystems, however, are threatened by a range of anthropogenic stressors (Dahanukar et al. 2011;Kumar et al. 2019). Around 340 species of freshwater fishes are known from the Western Ghats till date, of which more than 60% are endemic (Dahanukar & Raghavan 2013).
Despite several studies on freshwater fish fauna of southern Western Ghats, most upstream tributaries of major river systems continue to remain underexplored. Kabini is one of the major tributaries of the east flowing Cauvery River, originating from the Wayanad region of the Western Ghats. Studies on freshwater fishes of Wayanad date back to Jerdon (1847Jerdon ( , 1849 and Day (1867) who described several species from the region, but the first comprehensive list of freshwater fishes of Wayanad was compiled only in the 1990s (Shaji & Easa 1995). Three species, viz., Pethia pookodensis (Mercy & Jacob 2007), Pethia nigripinnis (Knight, Rema Devi, Indra & Arunachalam 2012), and Dario neela (Britz et al. 2018), were subsequently described from this region. Most upstream tributaries of Kabini, however, continue to be poorly studied and the diversity and distribution of fish species in the river system has not been investigated in a comprehensive manner over the past two decades. In this paper, we provide an overview of the diversity and distribution of fishes in the upper-catchment region of Kabini in Wayanad, identify threats to the river and its fish species, and suggest conservation plans.

Study Area
Kabini, also known as river Kapila is an important tributary of Cauvery which waters almost the entire part of the Wayanad Plateau. Kabini is an east flowing eighth order stream with a total basin area of 7,060.362km 2 spread across the southern Indian states of Kerala, Karnataka, and Tamil Nadu. A major part of its catchment area is in Mysore and Chamarajnagar districts of Karnataka. The river flows for around 250km before joining the main Cauvery River at Thirumakudal in Karnataka; however, in Kerala, Kabini is a seventh order stream with a catchment area of only about 1,934.5km 2 .
Wayanad has a total forest cover area of 907km 2 , divided into three major administrative divisions, viz., Wayanad Wildlife Sanctuary (344.44km 2 ), Wayanad North (214.94km 2 ), and Wayanad South forest divisions (347.66km 2 ). The forest patches in various sub-catchment regions of Kabini are represented by 118.9km 2 in the Panamaram sub-catchment, 167.8km 2 in the Mananthavady sub-catchment, 4.7km 2 in the Karapuzha Sub-catchment, 123.2km 2 in the Bavali subcatchment, 147.1km 2 in the Nugu sub-catchment, and 138.9km 2 in the Kabini sub-catchment. Nagarhole and Bandipur tiger reserves of Karnataka, and Mudumalai Tiger Reserve of Tamil Nadu are the other important protected areas in the Kabini Basin.

Mapping
The drainage basin of Kabini River was digitized prior to the study. For the delineation of catchments and subcatchments ArcGIS pro software and Arc Hydro tool was used. Cartosat V3.0 data was used for the delineation of the drainage basin. Streams were delineated using Arc Spatial analyst extension and hydrology tool. Drainage channels were ordered according to Strahler's (1957) classification.

Sampling sites and methods
Fish sampling was carried out from March 2014 to March 2020. A total of 89 different stream stretches were selected across various sub-catchments of the Kabini (Image 1), with sampling done at every 500m point of the total stream length (Image 2). GPS coordinates at each sampling location was recorded using standard digital GPS reader (Garmin eTrex 30x).
Fish were collected using monofilament gillnets, cast nets and scoop nets of varying mesh size, with the help of local fishers. Traditional fishing techniques like bund making, bamboo cage traps and sieving by cloth were also used in suitable areas. Only a minimum number of fish were collected for identification and the rest were released back into the stream, immediately after capture. Samples were fixed in 5% formaldehyde after

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anaesthesia with clove oil and later preserved in 70% ethanol. Samples for molecular studies were directly fixed in 80-99 % ethanol. Under the same sampling effort, we categorize records of 10 or less than 10 individual specimens of a species as 'very rare', 10-50 as 'rare', 50-100 as 'moderate', and more than 100 as 'common'. This classification is not based on any standard methodology or literature.

Species identification and morphometry:
Measurements were made with point to point using a digital-callipers to the nearest 0.1mm. Fish were identified by comparing the measurements and counts with the type/type series and/or as mentioned in the original description. Fish identification was confirmed using the relevant taxonomic literature for each group. Collected fish specimens are deposited in the museum collection of the Zoological Survey of India Western Ghats Research Centre, Kozhikode (ZSI WGRC) and the Laboratory of Systematics and Germplasm Conservation, Kerala University of Fisheries and Ocean Studies, Kochi (KUFOS). A few species could be identified only up to the generic level, as they showed significant variations in morphology from the currently known species. Some species which closely resembled known species whose specific status could not be confirmed due to a few marked differences in morphology were labelled with cf. (confusion). Specimens which could not be identified up to species level and some species with confusing identity have not been deposited in the museum collection as further studies on them are in progress, while some other species including most of the non-native species could not be preserved due to different logistic reasons (e.g., large size). We follow Nelson et al. (2016); Tan & Armbruster (2018) for family status while overall taxonomy and nomenclature follows Fricke et al. (2020).

Diversity and distribution
A total of 136 fish species belonging to 13 orders, 29 families and 69 genera were recorded from the study area (Table 1). Cypriniformes was the most dominant order with five families, 36 genera and 84 species, followed by Siluriformes with seven families, 11 genera and 21 species. Cyprinidae was the most dominant family represented by 51 species belonging to 21 genera, followed by Danionidae (19 species within eight genera) and Nemacheilidae (11 species within four genera). Lack of detailed taxonomic and systematic revisions have rendered the diversity of several groups of fishes in the Western Ghats to be obscure. The specific identity of 45 species collected during the present study could not be confirmed. We refrain from citing some recent publications in predatory journals following the journal policy (see Raghavan et al. 2015). Among the 91 species with confirmed specific identity, 44 are endemic to the Western Ghats, of which 16 are endemic to the Cauvery River System (Image 15a-d, Image 16e,g,i,k and Image 17a-h) and two species are currently known only from the Kabini Catchment (Image 15a, Image 17g). A total of 20 non-native fish species were also recorded from the study area, of which six species were inter-basin transplants within India, and 14 species were exotic to the country. Among the 74 native species with confirmed specific identity, four are Critically Endangered (CR) (Image 15a-d), nine Endangered (EN), three Vulnerable (VU), four Near Threatened (NT), 44 Least Concern (LC), and one species Data Deficient (DD). The conservation status of a further eight species have not yet been assessed.
Seventeen species (Table 2) which were earlier reported from Kabini could not be collected during the present study. Voucher specimens of these species are not available and based on the latest taxonomic literature, many are assumed to be misidentifications.
Kabini River Basin, identified as a freshwater Key Biodiversity Area (IUCN 2014) is among the regions of Western Ghats with the highest richness and endemism of freshwater faunal groups (Molur et al. 2011). The present study revealed that the river system is exceptionally rich in ichthyofaunal diversity. The total species richness of 136 is higher than many of the studied rivers in Kerala including the Bharathapuzha (117 species) (Bijukumar et al. 2013), and the Chalakkudy (98 species) (Raghavan et al. 2008). It is also important to note that the present study only surveyed the uppercatchment region of Kabini falling within the state boundary of Kerala and a detailed study in the lower reaches of the river and the tributaries in Karnataka may lead to more species being added into the list.
All six sub-catchment regions of Kabini support good numbers of endemic and threatened fish species, and have equal conservation value. Higher order streams running through forests (Images 6, 7 and 8) supported J TT the highest number of species, while several endemic species like Neolissochilus wynaadensis, Pterocryptis wynaadensis, Dario neela, loaches belonging to the family Nemacheilidae and Balitoridae and a few catfishes of the family Sisoridae could be recorded only from the lower order hill streams (Image 3,4 and 5) which are comparatively less disturbed.
Though we studied several streams in the region during the survey span of six years, records of more species are expected and further taxonomic studies are essential for calculating the true diversity of fishes in this region. It was noted that the assemblage and diversity of fishes are greatly dependent on the climatic conditions and vary between seasons, with several species available only during the monsoon.

Range extensions and first records
Our study revealed the presence of several species which were previously not recorded from Wayanad, and from the east flowing river systems. Laubuka fasciata (Image 16j), Hypselobarbus kurali (Image 16d), Sahyadria denisonii (Image 16f), and Puntius mahecola (Image 16h) are species considered endemic to the west flowing streams of Western Ghats (Abraham 2011a,b;. All four species mentioned above were recorded from various locations (Table 3) within the Banasura Sagar Reservoir and could not be collected from any other part of the Kabini catchment. This suggests that the four species could have either been introduced to the reservoir, or might be inter-basin migrants between Kuttiyadi and Kabini rivers, facilitated by a feeder canal which connects the Banasura Sagar Reservoir with the Kakkayam Reservoir built across the west flowing Kuttiyadi River (Image 2). It is currently not understood what the nature and population status of these species inside the reservoir are, as their presence is known only from a few specimens. Juvenile specimens of H. kurali and S. denisonii, however, were collected during the present study, which confirms that both species are breeding within the reservoir limits. Sahyadria denisonii is also one of the most traded ornamental fishes ) and therefore the possibilities of introduction of this species into the Kabini Basin by aquarist and breeders needs to be considered. Laubuka fasciata, H. kurali, and P. mahecola are, however, rare native species which are not commonly found in the ornamental fish trade in Kerala, and there are less likely chances of the introduction of these species into the reservoir, further supporting the idea of inter-basin migration. A feeder canal is also suspected to facilitate the movement of fish species endemic to Cauvery River System into the Kuttiyadi Basin (Gopi 2006). There is, however, no conclusive evidence to prove these speculations, and until any further information becomes available, all four species are considered native to the study region.

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Opsarius malabaricus (Image 16a), described from northern Malabar was considered as a synonym of Opsarius bakeri until , cleared the identity of the two species, based on collections from west flowing Payaswini and Valapattanam rivers of Kasargod and Kannur districts. Ten specimens of this species were collected from two locations (Table 3), within the catchment area of Banasura Sagar Reservoir, where they are rarely seen.
Laubuka trevori (Image 16e), is a recently described species from the Cauvery Catchment in Coorg District of Karnataka. This species was recorded from four different locations (Table 3) within the Kabini Catchment, extending the range of this species to the Kerala part of the Western Ghats.
In Kerala, Opsarius bendelisis (Image 16c) is known only from Chinnar and Pambar rivers of Amaravati Catchment in Idukki District (Easa & Shaji 1996). Our study confirms the range extension of this species to northern Kerala and for the first time from the Kabini Catchment.
Puntius cauveriensis (Hora, 1937) (Image 16i) is an endangered barb, endemic to the Cauvery River System in Karnataka, with records from Ithipuzha and Malampuzha in west flowing Bharathapuzha requiring confirmation (Shaji 2011). In our study, we recorded P. cauveriensis from seven different locations (Table 3) within the Kabini Catchment extending the range of this species to the Kerala part of Western Ghats.
Oreichthys coorgensis (Image 16g) is a poorly known species of small barb known only from the upper reaches of the Cauvery River in Coorg District of Karnataka (Knight & Kumar 2015). We report the range extension of this species to the Kerala part of Western Ghats with specimens collected from a single location (Table 3) within Kabini Catchment.

Pethia pookodensis (Image 15a) is a Critically
Endangered small-sized barb endemic to Wayanad, with confirmed records only from the Pookode Lake in Wayanad, the type locality . During our study, the species was recorded from all the sub-catchments of Kabini, confirming their occurrence outside the type locality, and its wide distribution range. A reappraisal of the conservation status of the species is hence required.
Mesonoemacheilus pambarensis (Image 16k), currently known only from Chinnar and Pambar rivers of Amaravati Catchment in Kerala, and from the Bhavani River in Tamil Nadu  was collected from four different locations (Table 3) in Wayanad, extending the range of this species to northern Kerala.
Hypselobarbus curmuca (Image 16b) and Pseudosphromenus cupanus (Image 16l), which were not recorded from Wayanad in previous ichthyofaunal studies were recorded in our study. Hypselobarbus curmuca was found be to be very rare in Kabini with records only from two locations (Table 3), while Pseudosphromenus cupanus is widely distributed in the basin with records from all the major tributaries of Kabini.

Major threats
Deforestation and removal of riparian vegetation (Image 9), pollution (Image 13), stream channel modification, sand mining, destructive fishing practices, dams & other impoundments, monsoon fishing, and non-native species are the major threats to freshwater fishes in the region. Riparian vegetation along Kabini and its major tributaries are severely disturbed, and in many cases totally destroyed. Over the past few decades, the natural vegetation across many of the streams has been cleared for agricultural plantations and construction.

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The Kuruva-Vettathur River Islands (Images 1,7 and 8) is the only region in the Kabini main stem where the riparian vegetation is currently intact. Similarly, the stream stretches running through reserved forests and protected area network are the only reaches with intact or less disturbed riparian buffer. Most of the stream stretches outside forests are severely disturbed, with riparian vegetation completely removed, particularly evident in Panamaram, Karapuzha, and Mananthavady sub-catchments. Loss of forest cover negatively impacts freshwater fish and several other faunal groups, since the nutrient cycle in stream ecosystems are regulated by a healthy riparian buffer (Vannote et al. 1980;Junk et al. 1989;Pusey & Arthington 2003). In addition, several freshwater fish species in the Western Ghats exploit allochthonous food resources and use the flooded riparian forests as spawning grounds (Arunachalam 2000). Canopy cover is also important in regulating stream water temperature which in turn plays an important role in the distribution of fish communities (Marsh-Matthews & Matthews 2000). Indiscriminate sand and gravel mining poses irreparable damage to habitats in the Kabini. Even the smallest stream stretches in the region are exploited for sand. Large scale destruction of river beds due to sand mining for commercial purposes are evident in Panamaram River, Mananthavady River, and Kabini main stem (Image 12). Sand mining-related stream bank modifications resulted in mass failure of stream banks in several locations during the floods of 2018 and 2019.
Heavy siltation of streams due to deforestation and sand mining which modify the stream beds directly affects several endemic species as it degrades their breeding substrates (Dahanukar et al. 2011). Hill stream loaches of the families Balitoridae, Cobitidae, and Nemacheilidae, and several species of cyprinids including the Critically Endangered Neolissochilus wynaadensis and Tor remadevii are particularly vulnerable to siltation.
Indiscriminate fishing, often using destructive practices such as dynamiting and poison fishing is

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observed in almost all the major sub-catchments of Kabini. Monsoon triggers the local migration of several fish species from large rivers into smaller streams, flooded marsh lands (Image 10), paddy fields and riparian forests, which serves as their spawning grounds. This mass movement of fishes is locally called 'ootha or ootha keattam" (Shaji & Laladhas 2013). Many of   (Image 14). Extreme climatic events increase the susceptibility of freshwater fishes to infections and disease outbreaks (Lopez et al. 2010), which was evident during the summer and post flood months of 2018 and 2019, when bacterial disease outbreaks resulted in widespread mortality of fishes at several locations in the Kabini catchment.

Conservation measures
Streams and rivers across the Kabini Catchment are severely threatened by a range of anthropogenic activities, leading to the fragmentation of available habitats. For the effective conservation of aquatic species in the river basin, a landscape-scale conservation strategy should be implemented, such that the complexity and diversity of the watershed is maintained. Longitudinal and lateral drainage network connections including lower order streams, head-water tributaries, upper-slope areas, wetlands and flood plains in the region should be maintained to provide un-obstructed corridors, to satisfy the life history requirements of several endemic species. River protection should be taken as a priority issue by the District Environmental Impact Assessment Authority (DEIAA) before giving clearances for activities such as mining, waste disposal plants and construction. To stop further ecological degradation of the river, we recommend that clearance should not be given to any large-scale constructional activities along the stream stretches, which includes dams, buildings and roads.
Structural diversity and species integrity of plant communities in wetland and riparian zones within the catchment should be conserved and the continuity of riparian forests can be maintained via restoration of degraded landscapes. Eco-restoration of the river can be initiated by the local self-governments by collaborating with non-governmental organizations, educational institutes and other public bodies like the Vana Samrakshana Samithi of the state forest and wildlife department.
It is also important to maintain the physical integrity of the ecosystems which include stream banks, shorelines and substrates. Regular monitoring of river sand extraction, recording the severity of extraction and periodic environmental auditing could prevent further degradation of river beds. Immediate actions are to be taken by the government to stop illegal sand mining in the region. Large scale conversion of floodplains and marshes for construction and unsustainable farming practices should be prohibited by strict implementation of the available laws. Actions should also be taken to stop the disposal of sewage water and domestic wastes into the river system.
Destructive fishing practices and indiscriminate harvest of fishes in Kabini, especially during the breeding seasons should be completely prohibited. The official ban on dynamiting and poisoning should be reinforced by the concerned authorities. Seasonal streams and marshes adjacent to the main river channels should be protected to secure the migratory corridors and spawning grounds of several native species.
Immediate actions are also to be taken to control the populations of exotic and invasive species in the river system and the introduction of new non-native species should be prevented. Farming and cultivation of nonnative species in the regions adjacent to river channels should not be promoted, and parties associated with such activities have to be made aware of the issue.
Designation of river reaches in reserved forest areas as fish sanctuaries or river sanctuaries with elevated protection level will also help in conserving the habitat and the species. Kuruva-Vettathur River Island region (image 1) in the Kabini main stem is a potential site which can be declared a riverine sanctuary.
Conservation and management of aquatic environments in the Kabini Basin require research involving inter-disciplinary approaches aimed at understanding the various aspects of landscape evolution, biodiversity and socio-economic vulnerability. Awareness campaigns involving researchers, students, farmers, fishing communities and other stakeholders can be arranged at local levels to create a network of people who can be employed for long-term monitoring and restoration of ecosystems.

Ichthyofaunal diversity in the upper-catchment of Kabini River
Thampy et al.