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Rheocles derhami 

Scope: Global
Language: English
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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Actinopterygii Atheriniformes Bedotiidae

Scientific Name: Rheocles derhami
Species Authority: Stiassny & Rodriguez, 2001

Assessment Information [top]

Red List Category & Criteria: Critically Endangered A2ac; B1ab(iii,v) ver 3.1
Year Published: 2016
Date Assessed: 2016-06-21
Assessor(s): Sparks, J.S.
Reviewer(s): Raminosoa, N., Randrianizahaisa, H., Rasoloariniaina, R, Ravelomanana, T. & Velosoa, J.
Contributor(s): Loiselle, P.V. & Participants of the CBSG/ANGAP CAMP "Faune de Madagascar" workshop, Mantasoa, Madagascar 2001
Facilitator/Compiler(s): Darwall, W.R.T.
Justification:
This species is only known from a single location, a tributary of the Sofia River in Madagascar. The species was formerly abundant in this area as recorded by Stiasnny et al. (1992) but surveys in 2013 (Tsilavina Ravelomanana, Brian Zimmerman et al.) found only one specimen despite extensive survey. Assuming the decline in habitat, which is the main ongoing threat, has occurred at a steady rate since 1992 it is also assumed that the resulting decline in the species population has also been linear. On this basis the species has declined from its former abundance to being very rare over a 10 year period and is assessed as Critically Endangered due to an inferred population decline of more than 90% in the last 10 years. As the species also has an EOO estimated to be less than 100 km² and the degradation and loss of habitat is ongoing it also qualifies as Critically Endangered under Criterion B.
Previously published Red List assessments:

Geographic Range [top]

Range Description:Rheocles derhami only known from Amboaboa and Mangarahara rivers in the Sofia drainage. Recent surveys (2013-2014) only found one specimen in Amboaboa near the Marotandrano village. No other subpopulations are found elsewhere (pers. obs.).
Countries occurrence:
Native:
Madagascar
Additional data:
Number of Locations:1
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:This species is only known from a single location, a tributary of the Sofia River in Madagascar. The species was formerly abundant in this area as recorded by Stiasnny et al. (1992) but surveys in 2013 (Tsilavina Ravelomanana, Brian Zimmerman et al.) found only one specimen despite extensive survey.
Current Population Trend:Decreasing
Additional data:
Continuing decline of mature individuals:Yes

Habitat and Ecology [top]

Habitat and Ecology:The species was formerly found in clear, pristine river habitat. It occurs in the upper part of the catchment where the water is relatively cool.
Systems:Freshwater
Continuing decline in area, extent and/or quality of habitat:Yes
Generation Length (years):1-3.3
Movement patterns:Not a Migrant

Use and Trade [top]

Use and Trade:

People consume this species locally.

Threats [top]

Major Threat(s):

This species is facing a significant degree of habitat loss, which is the main cause of its decline. Sedimentation changes the main river facies into shallow pools and runs. This kind of habitat is not suitable for this species especially when it is exposed to the sun, as the temperature climbs.  

This species also faces huge overfishing pressure. Local fishers use mosquito nets for fishing in the shallows and they practice poisoning in deep sections.

Conservation Actions [top]

Conservation Actions: The species receives no protection.

Citation: Sparks, J.S. 2016. Rheocles derhami. The IUCN Red List of Threatened Species 2016: e.T44659A58309105. . Downloaded on 10 December 2016.
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