|Scientific Name:||Neolissochilus hexagonolepis (McClelland, 1839)|
|Red List Category & Criteria:||Near Threatened ver 3.1|
|Reviewer(s):||Rema Devi, K.R., Vishwanath, W., Dahanukar, N. & Daniel, B.A.|
Although Neolissochilus hexagonolepis is apparently widespread, a number of the records require confirmation, and it is known with certainty only from India (Assam), Bangladesh and Myanmar. It is over-exploited in most of its range with populations in continuing decline and predicted to decline by more than 50% in the next 10 years due to over exploitation for fisheries, habitat loss and several human influenced changes. The species is assessed here as Near Threatened on the basis of inferred population decline, but may qualify for a higher threat category if further information becomes available on the species distribution and level of threat, including exploitation in fisheries.
|Range Description:||The species is recorded from Nepal (Gandaki, Trisuli, Koshi, Karnali, Mahakali river basins; Shrestha 2003), Bangladesh, Pakistan, Myanmar, Thailand, Malaysia (Peninsular), China, Indonesia (Sumatra), and India (Uttarakhand (introduced), Assam, West Bengal (Darjeeling Dt. and the Damodar river system), Arunachal Pradesh (E. Kameng Dt.), Meghalaya, Nagaland Rivers (Arachu, Dhansiri, Dikhu, Doyang, Intangki, Likhimro, Meguiki, Milak, Tesuru, Tizit, Tizu and Tsurang). Presence within other states in India within the Ganges basin is likely.|
Menon (2004) considered the species to be distributed in small in numbers through the eastern Himalayas in India (Assam), Bangladesh and Myanmar. Presence of this species in China is doubtful (Menon 1999), though it may be present in the tributaries of the Brahmaputra (Tsangpo) in Tibet and China. The records from Pakistan, Myanmar, Thailand, Malaysia (Peninsular), Indonesia (Sumatra) also need confirmation (N. Dahanukar, pers. comm., 2010). Kullander et al. (1999) surveyed the Kashmir valley (Indus drainage) and did not report the species.
The report of the species from Myanmar and Thailand may be due to misidentification because there is another species Neolissochilus stracheyi, which Day (1871) described from Akyab and Moulmein (Irrawaddy basin) in Myanmar. It is not known if the two species occur syntopically. But these are coldwater species, restricted to coldwater regimes and are not widely distributed.
Native:Bangladesh; India (Arunachal Pradesh, Assam, Bihar, Darjiling, Jharkand, Meghalaya, Nagaland, Uttar Pradesh, West Bengal - Introduced); Indonesia (Sumatera); Malaysia (Peninsular Malaysia); Myanmar; Nepal; Thailand
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||Much information is available on population decline due to habitat loss and over-exploitation. The species habitat has been lost due to the removal of sand and gravel, siltation caused by deforestation, pollution, and the construction of dams which degrade habitat and disrupt upstream breeding migrations (Menon 2004). It is inferred that the population has declined by 50-60% due to over exploitation of this species, and the occurrence has been limited to smaller areas. |
Our experience shows (and also informed by Dr. Debojit, pers. comm. 2010), there is great decline in its population. We know the flow modifications caused to northeast Indian waters (for example, the Teesta River) in Sikkim. We also know that due to global warming, coldwater regime has dwindled and warm water species have already invaded uplands.
Work on captive breeding of the species with the aim to release back into the wild is progressing, with studies on the population genetics of the species using polymorphic microsatellite markers and fast evolving regions of mtDNA with a view to initiate stock specific propagation assisted rehabilitation is progressing well in NBFGR (A. Gopalakrishnan, National Bureau of Fish Genetic Resources, pers. comm., 2010).
|Current Population Trend:||Decreasing|
|Habitat and Ecology:||Inhabits streams with fast flowing water mostly in high gradient and low gradient riffles and pools (Menon 1991). It prefers rocky and boulder areas with high flow. Siltation caused by deforestation could act as a threat.|
The species is known to breed from April to October with a peak in August to September. The male of this species mature at an early size of 9 cm. It breeds in pools with running water.
|Continuing decline in area, extent and/or quality of habitat:||Yes|
|Use and Trade:||This is a highly valued food and game fish which attains a length of over 60 cm and upto 11 kg.|
Major threats include habitat loss due to deforestation and erosion, urbanisation, including road construction, and over-exploitation. This migratory species is also threatened in parts of its range by current and planned hydropower developments e.g. the proposed Pancheshwar Dam in the Ganges basin on the border between India and Nepal (Everard and Kataria 2010).
Dams and weirs at higher reaches of the Brahmaputra have affected the spawning run of the fish (Menon 2004).
Conservation efforts are in action along with mahseer species because it is a co-occurring species.
|Citation:||Arunachalam, M. 2010. Neolissochilus hexagonolepis. The IUCN Red List of Threatened Species 2010: e.T166479A6217872.Downloaded on 16 August 2018.|
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