Chiloglanis bifurcus 

Scope: Global, Pan-Africa & Southern Africa
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Actinopterygii Siluriformes Mochokidae

Scientific Name: Chiloglanis bifurcus Jubb & Le Roux, 1969
Common Name(s):
English Incomati Suckermouth
Taxonomic Notes: Work in progress (Bloomer et al.) suggests that Chiloglanis do not migrate very much. An analysis of population structuring would be valuable to nature conservators when developing managements plans.

Assessment Information [top]

Red List Category & Criteria: Critically Endangered A2ace ver 3.1
Year Published: 2017
Date Assessed: 2016-11-30
Assessor(s): Roux, F. & Hoffman, A.
Reviewer(s): Weyl, O. & Raimondo, D.
Contributor(s): Engelbrecht, J. & Bills, R.
Facilitator/Compiler(s): Van Der Colff, D.
Incomati Suckermouth (Chiloglanis bifurcus) is endemic to the Upper Crocodile River and Elands River of the Inkomati River System, South Africa (Jubb & Le Roux 1969; Gaigher 1969; Kleynhans 1982, 1984, 1986; Skelton 1987; Kleynhans et al. 1992) and in the Upper Mlumati River in Swaziland (Monadjem et al. 2003, Bills et al. 2004). The population has declined since 1984 with the construction of the Kwena Dam (formerly Braam Raubenheimer Dam) in the Crocodile River for irrigation purposes. Flow regulation is particularly relevant in this regard and is thought to be the main driver of the elimination of the subpopulation in the Crocodile River below this dam. The chemical spill from the SAPPI Paper Mill at Ngodwana (23 September 1989) into the Elands River, further accelerated the decline of this species. More recently, deteriorating water quality from Machadodorp has impacted on this species. These declines have been exacerbated by the introduction of invasive alien fish species (Roux and Selepe 2013). These declines have been observed, through continuous biomonitoring of the species and the determination of the Ecostatus of the Inkomati Catchment by nature conservation officials (MTPA – Mpumalanga Tourism and Parks Agency). Based on the trends of the catch per unit effort (CPUE) and relative abundance of this species a 90% population reduction has been observed over the past 10 years (estimated generation length of 3-5 years) (Kleynhans 1984, 1989; Roux & Selepe 2013; Roux et al. 2016). There has also been a decline in the area of occupancy (AOO), extent of occurrence (EOO) and a loss of habitat quality. It therefore qualifies as Critically Endangered under criteria A2ace.
Previously published Red List assessments:

Geographic Range [top]

Range Description:This species has a restricted distribution and is endemic to the Inkomati River System and within this system it is restricted to altitudes between 900 m.a.s.l to 1200 m.a.s.l. It historically occurred in the Crocodile and Elands River and in some of its sub-tributaries (Elands, Ngodwana, Gladdespruit and Stadspruit) (Kleynhans 1984). Recently only sampled from a small section of the Elands River and Crocodile River as well as in a few tributaries of the Mlumati River in South Africa and Swaziland.
Countries occurrence:
South Africa (Mpumalanga); Swaziland
Additional data:
Estimated area of occupancy (AOO) - km2:56
Number of Locations:3
Lower elevation limit (metres):900
Upper elevation limit (metres):1200
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:This mainstem species is naturally found at relatively low population densities and based on comprehensive population studies by Kleynhans (1984) its historic relative abundance in relation to other fish species sampled from appropriate habitat was 2.8% and catch per unit effort (CPUE) was 0.18 fish/minute electrofishing. O’Brien et al. (2014) assessed the different CPUE trends dating back to 1989 (Kleynhans 1992, James 1992) and also conducted seven fish surveys from March 2002 to August 2006. The CPUE rates during these surveys the for Incomati Suckermouth ranged between 0.04 and 1.73 fish/minute electrofishing, In 2013 the Mpumalanga Tourism and Parks Authority (MTPA) conducted a comprehensive study on the Ecostatus of the Crocodile River Catchment during which 56 biomonitoring sites were sampled (Roux and Selepe 2013). Chiloglanis bifurcus were only sampled from three of the 56 sampling sites, two in the Elands River and one in the Crocodile River, close to its confluence with the Elands River. In conjunction with a small number of sites from which this fish was sampled, the CPUE 0.06 fish/minute electrofishing was indicative of a drastic decline in the population. Particularly relevant was that no Incomati Suckermouth were recorded at the type locality in the Crocodile River downstream of the 50 m high Kwena Dam (formerly Braam Raubenheimer Dam). It would appear that stream regulation from the dam has had a detrimental effect on the downstream population of this species. During this study the species was also not recorded in the Houtbosloop tributary as intensive forest fires in 2010 resulted in excessive siltation and sedimentation altering and reducing its available habitat.In September 2013 and April 2014 high flow and low flow surveys were conducted to determine stream flow conditions in the Elands River relating to the impact of the Sappi Paper Mill at Ngodwana (Diedericks and Roux 2014). During the low flow period survey no Incomati Suckermouth were sampled despite the collection of 477 individuals of other fish species during an electrofishing sampling effort of 97 minutes. During the high flow period surveys only four adults were recorded, resulting in a CPUE of 0.04 fish/minute electrofishing and a relative contribution to the fish community of 1.23%. Thus for both the high and low flow surveys the average combined CPUE value was 0.02 and a population density of 0.49%. In comparison to the historical CPUE of 0.18 fish/minute electrofishing the 2013/14 survey indicated a decline in the population density of Incomati Suckermouth (Kleynhans 1986). In 2016 an intensive study was conducted to determine the overall status of the Incomati Suckermouth population across its extent of occurrence. In the Ngodwana River, described as a sanctuary area (James 1992), three adult individuals were collected from two sites that were surveyed with a combined sampling effort of 138 minutes resulting in a CPUE value of 0.02 individuals/minute electrofishing (relative abundance= 0.24%). This observed reduction can possibly be related to the presence of the invasive alien species such as Rainbow Trout (Oncorhynchus mykiss). For the other seven biomonitoring sites on the Elands River and tributaries only ten adults were sampled with a CPUE value of 0.03 (relative abundance = 0.36%). These recent surveys indicate that the population in the Elands River catchment and tributaries has suffered a >90% reduction in distribution and a decline in AOO as well as a loss of habitat quality. Further, the subpopulation in the Crocodile River reach below the Kwena Dam is likely to be extinct and the population recorded in the Ngodwana River is now fragmented and threatened by alien fishes. For the subpopulation recorded in the Upper Mlumati River, Swaziland, very little information is available. However, due to unregulated forestry activities, most of these streams in Swaziland are severely sedimented and it is suspected that this subpopulation is also at risk.
Current Population Trend:Decreasing
Additional data:
No. of subpopulations:3

Habitat and Ecology [top]

Habitat and Ecology:This is a instream species with adults ranging from 4.1 cm to 6.7 cm and occurs in rocky habitats in fast flowing streams and rivers, but typically inhabits deeper runs rather than rapids. The average flow velocity in the Crocodile River where this species occurs range from 0.35 m sec-1 to 1.16 m sec-1 with a depth ranging from 0.3 – 1.5 m and the river width ranging between 5 to 8 m (Kleynhans 1984). This species inhabit the interstitial spaces of lose rocks with a diameter ranging from 0.1 m to 0.5 m. They occur in relative low population densities together with several other fish species which include Common Mountain Catfish (Amphilius uranoscopus), Rosefin Barb (Enteromius argenteus) and Shortspine Suckermouth (Chiloglanis Pretoriae) (Kleynhans 1984). This species breeds in the summer from October to February and is classified as a partial spawner with total fecundity of between 250 and 300 ova. The precise spawning habitat has not been identified.
Continuing decline in area, extent and/or quality of habitat:Yes
Generation Length (years):3-5

Threats [top]

Major Threat(s): In the Inkomati River System, the Crocodile River below the Kwena Dam, the population has gone extinct from its type locality. This is probably due to continuous flow regulation from the Kwena Dam. In the Elands River additional impacts within the region are deteriorating water quality from Machadodorp (Ferrochrome smelter, Machado waste water treatment plant and informal settlements). Further downstream it is impacted by sedimentation from forestry and agricultural activities, water extraction resulting in reduced or no flows, as well as introduced alien fishes (Brown Trout (Salmo trutta), Rainbow Trout (Oncorhynchus mykiss) and Largemouth Bass (Micropterus salmoides)). The SAPPI Ngodwana Paper Mill and related activities is a present form of pollution and according to Griffin et al. (2014) the Elands River is one of the most impacted rivers in the catchment. The assessment of water quality changes with time show a clear temporal quality decrease and a distinct cumulative impact with distance downstream. In the other Elands River tributaries (Ngodwana, Gladdespruit, Stadspruit and Houtbosloop) forestry related practices with high road network densities and stream crossings resulted in excessive sedimentation and the loss of habitat availability to this species, resulting in the disappearance of this species in most of these streams. Large forestry fires in 2010 furthermore attributed to sedimentation of instream fish habitats. In the upper Mlumati River, Swaziland, similar conditions relating to unregulated forestry threatens this species.

Conservation Actions [top]

Conservation Actions: The distribution range of Incomati Suckermouth is entirely within privately owned land without any formal conservation protection. The two remaining subpopulations need to be given priority for conservation efforts. Land and water use practices need to be carefully managed and stocking of alien organisms need to be stopped. The most effective way might be through conservancy agreements with riparian land owners and the Mpumalanga Parks Board. The Elands River and its tributaries have been identified as priority freshwater environments for fish conservation and are listed as a fish sanctuary in the National Freshwater Ecosystem Priority Areas (NFEPA) (Driver et al. 2011).

Citation: Roux, F. & Hoffman, A. 2017. Chiloglanis bifurcus. The IUCN Red List of Threatened Species 2017: e.T4632A100193958. . Downloaded on 22 September 2018.
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