Nemacheilus triangularis 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Actinopterygii Cypriniformes Balitoridae

Scientific Name: Nemacheilus triangularis Day, 1865
Common Name(s):
English Zodiac Loach
Mesonoemacheilus triangularis (Day, 1865)
Mesonoemacheilus triangularis (Day, 1865)
Noemacheilus triangularis tambaraparniensis Menon, 1987
Taxonomic Notes: Nemacheilus triangularis was described by Day in 1865.  The subspecies designated as N. triangularis tambarapaniensis Menon, 1987 from Tambaraparani River may be a distinct species.  Presently it is synonymised under this species (Menon 1987, M. Arunachalam pers. com.).

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2011
Date Assessed: 2010-06-21
Assessor(s): Abraham, R.
Reviewer(s): Rema Devi, K.R., Gopalakrishnan, A., Arunachalam, M., Shrikant, J., Johnson, J.A., Rahul, K. & Molur, S.
Contributor(s): Molur, S.
Nemacheilus triangularis is a widely distributed species occurring in the Western Ghats of three states of southern India.  Although the species is harvested for aquarium trade and there is no monitoring, the population trends in this commonly occurring and abundant species is stable, hence Least Concern.

Geographic Range [top]

Range Description:Nemacheilus triangularis is endemic to the Western Ghats, widespread in southern Karnataka, Kerala and Tamil Nadu  (Menon 1987, Devi et al. 1997, Shaji & Easa 2003, Johnson and Arunachalam 2009, Jayaram 2010).  It is commonly found in almost all west flowing rivers and in some east flowing rivers in southern India (Tamil Nadu) (Remadevi pers. comm.).
Countries occurrence:
India (Karnataka, Kerala, Tamil Nadu)
Additional data:
Estimated area of occupancy (AOO) - km2:1800
Number of Locations:32
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:It is a fairly common species, abundant in its range (R. Abraham pers. obs.). There is no literature on the population trends of this species.
Current Population Trend:Stable
Additional data:
Population severely fragmented:Unknown

Habitat and Ecology [top]

Habitat and Ecology:Nemacheilus triangularis is a benthic species that are found in both highland and midland areas, preferring oxygenated clear water streams with gravel, cobbles and bedrock with a little amount of sand as the substrate. They are a territorial, omnivorous and forage fishes for larger species (Chhapgar & Manakadan 2000, Biju 2003).
Continuing decline in area, extent and/or quality of habitat:Yes

Use and Trade [top]

Use and Trade: Nemacheilus triangularis is collected for the aquarium trade. But, levels of off-take from the wild has not been monitored. Not a targeted food fish.

Threats [top]

Major Threat(s): The species is threatened by widespread deterioration and transformation of its habitat for agricultural expansion and developmental activities including recent spurt in tourism development resulting in the damming of rivers, submerging large areas of habitat as well as pollution from tourism and agricultural sources. In recent years many streams in the species range have been threatened by habitat alterations caused by sand mining, and exploitative fishing by poisoning and explosives, despite not being the targeted species (R. Abraham pers. obs. November 2009).

Conservation Actions [top]

Conservation Actions: Some areas of the species' habitat falls in protected areas. Outside PAs, there are no conservation measures of any kind and the threats are escalating.  Captive breeding technology has been developed (Mercy et al. 2007).

Classifications [top]

5. Wetlands (inland) -> 5.1. Wetlands (inland) - Permanent Rivers/Streams/Creeks (includes waterfalls)
suitability:Suitable  major importance:Yes
1. Land/water protection -> 1.1. Site/area protection
1. Land/water protection -> 1.2. Resource & habitat protection

In-Place Research, Monitoring and Planning
  Action Recovery plan:No
  Systematic monitoring scheme:No
In-Place Land/Water Protection and Management
  Conservation sites identified:Yes, over part of range
  Occur in at least one PA:Yes
  Area based regional management plan:No
  Invasive species control or prevention:No
In-Place Species Management
  Harvest management plan:No
  Successfully reintroduced or introduced beningly:No
  Subject to ex-situ conservation:No
In-Place Education
  Subject to recent education and awareness programmes:No
  Included in international legislation:No
  Subject to any international management/trade controls:No
1. Residential & commercial development -> 1.3. Tourism & recreation areas
♦ timing:Ongoing ♦ scope:Minority (<50%) ♦ severity:Negligible declines ⇒ Impact score:Low Impact: 4 
→ Stresses
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation
  • 2. Species Stresses -> 2.2. Species disturbance

5. Biological resource use -> 5.4. Fishing & harvesting aquatic resources -> 5.4.3. Unintentional effects: (subsistence/small scale) [harvest]
♦ timing:Ongoing ♦ scope:Minority (<50%) ♦ severity:Unknown ⇒ Impact score:Unknown 
→ Stresses
  • 2. Species Stresses -> 2.2. Species disturbance

7. Natural system modifications -> 7.2. Dams & water management/use -> 7.2.10. Large dams
♦ timing:Past, Unlikely to Return ♦ scope:Minority (<50%) ♦ severity:Rapid Declines ⇒ Impact score:Past Impact 
→ Stresses
  • 1. Ecosystem stresses -> 1.1. Ecosystem conversion

7. Natural system modifications -> 7.2. Dams & water management/use -> 7.2.9. Small dams
♦ timing:Past, Likely to Return ♦ scope:Minority (<50%) ♦ severity:Causing/Could cause fluctuations ⇒ Impact score:Past Impact 
→ Stresses
  • 1. Ecosystem stresses -> 1.1. Ecosystem conversion

8. Invasive and other problematic species, genes & diseases -> 8.1. Invasive non-native/alien species/diseases -> 8.1.1. Unspecified species
♦ timing:Ongoing ♦ scope:Majority (50-90%) ♦ severity:Causing/Could cause fluctuations ⇒ Impact score:Medium Impact: 6 
→ Stresses
  • 1. Ecosystem stresses -> 1.2. Ecosystem degradation
  • 2. Species Stresses -> 2.2. Species disturbance
  • 2. Species Stresses -> 2.3. Indirect species effects -> 2.3.2. Competition

1. Research -> 1.1. Taxonomy
1. Research -> 1.2. Population size, distribution & trends
1. Research -> 1.3. Life history & ecology
1. Research -> 1.5. Threats
3. Monitoring -> 3.1. Population trends
3. Monitoring -> 3.2. Harvest level trends
3. Monitoring -> 3.3. Trade trends
3. Monitoring -> 3.4. Habitat trends

♦  Food - human
 Local : ✓ 

♦  Pets/display animals, horticulture
 National : ✓  International : ✓ 

Bibliography [top]

Biju C. R. 2003. Habitat and Distribution of Hillstream fishes of Northern Kerala. Department of Zoology, Mahatma Gandhi University.

Chhapgar, B.F. and Manakadan, R. 2000. Ecology of Hill Streams of Western Ghats with Special Reference to Fish Community. US Fish and Wildlife Service & Bombay Natural History Society, Bombay.

Devi, R., T.J.Indira, M.B. Raghunathan, M. Marybai and M.S. Ravichandran. 1997. Ichthyofauna of the Tambaraparani River system, Tamil Nadu. Zoos' Print 12(7): 1-2.

IUCN. 2011. IUCN Red List of Threatened Species (ver. 2011.1). Available at: (Accessed: 30 June 2017).

Jayaram, K.C. 1981. The freshwater fishes of India, Pakistan, Bangladesh, Burma and Sri Lanka - a handbook..

Jayaram, K.C. 2010. The Freshwater Fishes of the Indian Region. Narendra Publishing House, Delhi.

Johnson, J. A. and Arunachalam, M. 2009. Diversity, distribution and assemblage structure of fishes in streams of southern Western Ghats, India. Journal of Threatened Taxa 1(10): 507-513.

Menon A.G.K. 1987. The Fauna of India and Adjacent Countries (Pisces - Teleostei - Cobitidea - Homalopteridae). Zoological Survey of India, Calcutta.

Menon, A. G. K. 1987. The fauna of India and the adjacent countries. Pisces. Vol. IV. Teleostei - Cobitoidea. Part 1. Homalopteridae. Zoological Survey of India.

Mercy, T.V.A and Jacob, E. 2007. A new species of Teleostei: Puntius pookodensis (Cyprinidae) from Wayanad, Kerala, India. Journal of the Bombay Natural History Society 104(1): 76-78.

Shaji, C.P. and Easa, P.S. (eds). 2003. Freshwater fishes of Kerala. pp. 125. Kerala Forest Research Research Institute (KFRI), Thrissur.

Citation: Abraham, R. 2011. Nemacheilus triangularis. In: . The IUCN Red List of Threatened Species 2011: e.T172434A6891437. . Downloaded on 21 June 2018.
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