Pachypanchax arnoulti 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Actinopterygii Cyprinodontiformes Aplocheilidae

Scientific Name: Pachypanchax arnoulti Loiselle, 2006
Pachypanchax sp. nov. 'Betsiboka'
Taxonomic Source(s): Eschmeyer, W.N., Fricke, R. and Van der Laan, R. (eds). 2016. Catalog of Fishes: genera, species, references. Updated 2 May 2016. Available at: (Accessed: 2 May 2016).
Taxonomic Notes: This species appeared on the IUCN Red List as Pachypanchax sp. nov. 'Betsiboka' until 2016. This species was formally described as Pachypanchax arnoulti in Loiselle (2006). An updated Red List assessment has been created to reflect this change.

Assessment Information [top]

Red List Category & Criteria: Vulnerable B1ab(iii) ver 3.1
Year Published: 2016
Date Assessed: 2016-06-15
Assessor(s): Sparks, J.S. & Loiselle, P.V.
Reviewer(s): Randrianizahaisa, H., Rasoloariniaina, R, Ravelomanana, T. & Velosoa, J.
Contributor(s): Participants of the CBSG/ANGAP CAMP "Faune de Madagascar" workshop, Mantasoa, Madagascar 2001
Facilitator/Compiler(s): Darwall, W.R.T.
This species is recorded from rivers on the western slopes of Madagascar from the Betsiboka-Kamoro basin to the Tsiribihina and including Lac Kinkony. However, the Betsiboka/Ikopa and Kinkony subpopulations are impacted by loss of habitat and exotic fishes colonisation. The extent of occurrence is less than 20,000 km², it is found in only four locations, and there is an ongoing decline in habitat. This species is assessed as Vulnerable.
Previously published Red List assessments:

Geographic Range [top]

Range Description:This species is endemic to Madagascar. According to Loiselle (2006), Pachypanchax arnoulti is native to the basins of the Mahavavy du Sud and the Betsiboka, to the small independent streams that flow into the Mozambique Channel between the estuaries of the Betsiboka and Mahavavy du Sud, and to Lake Kinkony and its satellite lakes. It has also been collected from a hill stream draining the Tampoketsa highlands, which crosses the Antananarivo-Maevatanana road at the Kilometre 240 marker, 53 km east of the town of Maevatanana, and from the upper Kamoro drainage (P. de Rham pers. comm.). Its presence in the Mahajamba drainage, which lies to the north of the Betsiboka and is connected to it by the Kamoro, is probable but has yet to be confirmed.
Countries occurrence:
Additional data:
Number of Locations:4
Range Map:Click here to open the map viewer and explore range.

Population [top]


According to Loiselle (2006), the conservation status of P. arnoulti varies over its extensive range. During the past fifty years, its numbers have declined significantly within the Betsiboka-Ikopa drainage. Recent efforts to recollect this species from streams near the town of Maevatanana, where Arnoult (1955) found it to be abundant, were unsuccessful. These localities now are home to substantial populations of naturalized Xiphophorus hellerii. This species has also become very rare in the Ampijoroa Forest Reserve, where Arnoult collected a large series of specimens in the 1960's (J. S. Sparks, pers. com.), N. Raminosoa (pers. com.) reported that it is still abundant in satellite lakes of the Kinkony basin in the delta of the Mahavavy du Sud but recent survey contradicts it, it is becoming rare (Ravelomanana T. unpublished data) and appears to be under significant pressure from X. hellerii at the type locality and from G. holbrooki in the lower reaches of the Kamoro (P. deRham, pers. com.). However, it remains abundant in both the upper Kamoro River and in the small streams situated between the mouths of the Betsiboka and Mahavavy du Sud (P. de Rham., pers. com.).

Current Population Trend:Decreasing
Additional data:

Habitat and Ecology [top]

Habitat and Ecology:

According to Loiselle (2006), Pachypanchax arnoulti has been collected from a wide range of habitats. The type locality is a Pandanus-Dracaena swamp, whose waters are clear, tannin stained, acidic (pH of 6.2), soft (total hardness < 17.1 ppm), and deficient in dissolved substances (electrical conductivity 16 ìS/cm2). Neither filamentous algae nor vascular aquatic plants were present. This species was also collected in a small creek flowing into the Akalimolitra River, a tributary of the Betsiboka, and was observed in the shallows of the main channel of the Akalimolitra proper. Its waters were clear, colorless, with a neutral pH, moderate hardness (total hardness 68.4 ppm), and deficient in dissolved substances (electrical conductivity 34 ìS/cm²). Neither filamentous algae nor vascular aquatic plants were present in either the main channel of the Akalimolitra or its tributary.

Continuing decline in area, extent and/or quality of habitat:Yes
Movement patterns:Not a Migrant

Use and Trade [top]

Use and Trade: There is not trade or use information available for this species.

Threats [top]

Major Threat(s): In the Kinkony and surrounded satellite lakes, local fishermen use very large seine nets with a small  seize mesh for catching Sauvagella madagascariensis and Acentrogobius therezieni. This kind of practice takes all fishes present in the area and it results the decline of the population (Ravelomanana T. pers. obs. 2002). Loiselle (2006) noted that Xiphophorus hellerii displaces Pachypanchax arnoulti.

Conservation Actions [top]

Conservation Actions: Three protected areas are included within the range of Pachypanchax arnoulti : The "Complexe Mahavavy Kinkony", Ankarafantsika and Bombetoka Belemboka.

Citation: Sparks, J.S. & Loiselle, P.V. 2016. Pachypanchax arnoulti. The IUCN Red List of Threatened Species 2016: e.T44484A58307322. . Downloaded on 22 September 2018.
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