Ichthyological survey and review of the checklist of fish fauna of Arunachal Pradesh, India

One hundred thirty eight fish species were collected during a systematic survey of 35 rivers in Arunachal Pradesh state, India, in March 2004 to March 2008. Based on this survey and on literature review we developed a checklist with 213 fish species for the state. We have added 43 species to the previous record of 170 species. This study confirmed the occurrence of five new species described by previous investigations and encompasses the discovery of two new species, although the taxonomic status of 27 species is uncertain and requires additional study


Introduction
Fish are invariable living components of water bodies. These organisms are important food resource and good indicators of the ecological health of the waters they inhabit. However, the rich biodiversity of the freshwater fish of the Indian region has been rapidly dwindling because of increasing degradation of inland water. Out of a total of 2,500 species of fish in India, 930 are in fresh waters and belong to 326 genera, 99 families and 20 orders (Talwar and Jhingran 1991). Arunachal Pradesh (AP) state is the largest in geographical as well as in river drainage area in North-Eastern India and harbours innumerable rivers and rivulets which are home to diverse fish species, of which many are endemic to this region. AP is regarded as the type locality for more than 11 freshwater fish species in the world.
The fish resources in the lotic systems had not been completely explored because most of the rivers are located in unapproachable mountainous steep terrain with dense forest cover. The forest cover of the state, based on satellite data of February 2005, is 67.78 km 2 (80.93 %) and due to low human density large areas of forest still remain intact.
In recent years the number of studies on fishery resources of the state have increased. For example, Nath and Dey (2000) published their pioneering works on systematic account of fish resources of AP revealing 131 species from AP. Moreover, two new species have been described recently: Pseudechenies sirenica Vishwanath and Darshan 2007 and Psilorhynchus arunachalensis (Nebeshwar, Bagra and Das 2007). These publications suggest that water bodies of AP are of taxonomic importance.
Besides the probable importance of this system, we have found a gap of information regarding the list of fish fauna in the drainage systems of the state. By this reason, the aim of the study was to catalogue the fish species diversity in AP state and to establish a museum of fish resources of Arunachal Pradesh -the first of this kind in the state, at the Centre of Biodiversity in Rajiv Gandhi University, Rono Hills, Itanagar.

Material and methods
Arunachal Pradesh (AP) state is situated in the North-Eastern part of India between 26° 28' to 29° 30' N and 90° 30' to 97° 30´ E, with 83,743 km 2 total area. Almost 95 % of the streams and rivers in the state drain in to the mighty river Brahmaputra and the rest drain in to Irrawaddy river drainage of Chindwin basin. The river Brahmaputra also receives water from the state Assam and ultimately discharges the contents in to the Bay of Bengal. The river Siang is the biggest river in AP which is originated in Tibet where it is known as Tsangpo. The major rivers traversing the state are Lohit, Dibang, Siang, Siyom, Subansiri and Kameng. We surveyed 40 randomly selected stations in 35 streams and rivers in the state during a period of four years from March 2004 to March 2008. Fishes were collected with the following methods: viz. elctrofisher (Samus-725G), cast nets, gill nets and indigenously used fishing contraptions. During the field activities, we also used formalin for preserving the specimens, GPS (Garmin eTrex Legend) for recording the geographical coordinates and digital camera (Sony DSC-W30) for registering the specimens. At each randomly selected sampling station the maximum possible length of the stream/ river was covered and attention was paid to sample fishes from maximum heterogeneous habitat types.
The indigenously used fishing devices, their construction and the methods of application are described below: i) Takom gaanam: technique of placing a Takom in the river or stream. Takom is a conical shaped fish trap made of bamboo with a mouth diameter ranging from 0.1 to 0.3 meter. It is fixed against the water current. Once the fish entered inside, they remained entangled in the base with the pressure of water current. ii) Tasum kunam: fishing method in which a conical shaped basket made of cane is used to collect fishes from streams or rivers. With this fishing gear small sized fishes, especially bottom dwellers, are easily collected. iii) Lipum paanam: fishing method in which the flat stones are piled one on other in the pool or slow flowing river of approximately 1 meter depth. The stone are piled in such a way that forms a round shape of aggregated stone block called lipum. The diameter of lipum ranges from 1.2 to 2.0 meters and height ranges from 0.4 to 0.5 meter. Lipum paanam is practiced during winter season and is allowed to remain undisturbed for 2 to 3 months where fish used to take shelter. The aggregated fishes are then collected by unpiling stones just after cordoning the lipum with a circular screen made of bamboo. These indigenous devices were used where common fishing gears were not appropriated. The collected specimens were immediately dipped in 10 % formalin after removed from water in a spacious container that allowed proper spreading of their fins. Two to three changes of specimens in fresh formalin preparation of 10 % dilution was adopted during the sampling time. When necessary, peritoneal administration of the preservative has also been done. By the end of each sampling the specimens were examined on field and classified into different families; which were carried in separate containers. Each container was labeled properly against the physical data sheet of the sampling station and brought to the laboratory for further taxonomic exercise.
Morpho-taxonomic counts and identifications have been done following Kottelat (2001). Measurements were taken up to the one tenth of a millimeter using dial calipers.
The present checklist has been prepared as per the internationally accepted valid names available in the online catalog of fishes, California Academy of Sciences. The results of this study are presented in a way to provide relevant information, which includes number of the specimen examined, range of size group as standard length (SL), the registration number in the museum, site of collection, geographical co-ordinates of the collection site and a geographical map of the state indicating the collection sites. The station of collection, as pointed in the map, is presented in a tabular form mentioning the name of the station, the name of nearby town and the altitude of the respective sites.

Results and Discussion
A total of 138 fish species were collected and examined (Appendix 1) from 40 randomly selected stations in 35 rivers (Table 1) of Arunachal Pradesh (Figure 1) during the study period. From this total, 111 species were identified and confirmed at the species level, including 16 new occurrences for the study site. The remaining 27 species of the total collection are yet to be confirmed at species level. Comparing with previous studies, 75 such species registered for the region have not been recorded in the present collection (Appendix 2). Based on the valid name of both examined and consulted species, the current checklist of 213 fish species included in 11 orders, 31 families and 93 genera have been ascertained for the state.

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We have added 43 species to the previous record of 170 species, in a total of 213 fish species in the drainage system of the state. This study also confirmed the occurrence of five new species described by previous studies in the study site. Nevertheless, the study encompasses the discovery of two new species, though one of them is awaited for publication. Moreover, our study has been the first, to our knowledge, to cover the entire hydro-geographical locations at different altitude zones, which was hardly emphasized in any of the earlier works. Previous studies were also mostly fragmentary (e.g. McClelland 1839, Chaudhuri 1913Hora 1921;Jayaram 1963;Mazumdar 1964, Menon 1964;Dutta and Sen 1977;Choudhury andSen 1977, Jhingran andSehgal (1978). One of the only non-fragmentary studies on fish and fisheris in AP state has been the checklist of 131 species (see Nath and Dey 2000 for further details).
The identity of 27 type specimens in species level under different genera of our collection still remained uncertain due to morphotaxonomic variations from the described species under their respective genera. Moreover, the lower number of collections of certain type specimens in some genera caused hindrance for further taxonomic confirmation. Also, the lack of facilities either for exchange of voucher specimens or for consultation of holotypes in the established museums of the country and abroad remained as one of the reasons behind confirmation of species level identity of some collected genera within the study period. For example, species of Garra were very difficult to identify. Previous studies report 9 species of Garra for the state. Our collection consisted of 7 species of Garra, from which 3 could not be confirmed at the species level due to lack of museum voucher specimens. Thus, a total of 27 species (Figure 2 to 26, Appendix 3) were identified up to genera level and at this point of time they have been considered as new record from the state. Garra kalpangii sp. nov. ( Figure  27, Appendix 3) (awaiting publication in Zoos' Print Journal) has recently been described from the same study. As such, all the unconfirmed species may either be described as new species or may be confirmed as new report of known species from the state.
Some of the river sites of AP state have been reported as type locality of eleven fish species. From these 11 species, five were collected in our study (Amblyceps arunachalensis Nath and Dey 1989, Amblyceps apangi Nath and Dey 1989, Pseudecheneis sirenica Vishwanath and Darshan 2007, Aborichthys kempi Chaudhuri 1913 and Pareuchiloglanis kamengensis (Jayaram 1966)). The remaining six species were not found in our study but have been included in this checklist (Schistura tirapensis Kottelat 1990 2002). Further, the species competes with native species for food at all of their life stages. As juveniles, they feed on zooplankton, insect larvae, small crustaceans and eggs and fries of other fishes. As adults, the species become voracious predators, feeding upon other fishes, crustaceans, snails, frogs, small reptiles and aquatic and terrestrial insects. If the species establishes themselves in the lotic systems, their predatory behaviour could drastically modify the array of native species. As a result, they may disrupt the ecological balance of these native aquatic systems. As we collected five specimens of invasive species, ranging from 58 to 120 mm in SL, it is probable that the species have been able to establish natural population in the river.   ----------------Appendix 2. Fish species consulted during the study.