Austroglanis gilli 

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

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Actinopterygii Siluriformes Austroglanididae

Scientific Name: Austroglanis gilli (Barnard, 1943)
Common Name(s):
English Clanwilliam Rock Catfish
Gephyroglanis gilli Barnard, 1943

Assessment Information [top]

Red List Category & Criteria: Near Threatened ver 3.1
Year Published: 2017
Date Assessed: 2016-12-02
Assessor(s): Van der Walt, R., Jordaan, M., Bills, R. & Impson, D.
Reviewer(s): Raimondo, D., Raghavan, R. & Freyhof, J.
Facilitator/Compiler(s): Van Der Colff, D.
Clanwilliam Rock Catfish (Austroglanis gilli) is endemic to the Olifants-Doring River System (ODRS), South Africa, where it has been recorded from 16 tributaries (16 locations). Its extent of occurrence (EOO) is 2080 km2 (calculated using minimum convex polygon) and area of occupancy (AOO) is 196 km2 (calculated using a 2 km2 grid). Recent conservation efforts have increased the viability of two locations (Rondegat and Thee River). Five locations are located in formal conservation areas. In the previous assessment (2007) the number of locations was regarded as five now there are 16 locations identified, based on a better understanding of the criteria. However, these locations are currently still experiencing continuous decline in habitat quality and the extent of occurrence due to unsustainable water abstraction and other threats. The species was previously listed as Vulnerable but has been reclassified as Near Threatened B1b(i,iii)+2b(i,iii) due to conservation efforts and more information available on the number of locations.
Previously published Red List assessments:

Geographic Range [top]

Range Description:Clanwilliam Rock Catfish (Austroglanis gilli) is endemic to the Olifants-Doring River System (ODRS) in the Western Cape, South Africa. It occurs in tributaries of the Olifants (Ratel, Oudste, Thee, Noordhoeks, Boontjies, Boskloof, Heks, Rondegat, Jan Dissels, Dwars) and Doring (Biedouw, Tra Tra, Eselbank, Matjies, Krom and Breekkrans) basins of the ODRS and also occurs in the mainstream Olifants River near the Heks tributary (Bills 1999, Van der Walt 2016).
Countries occurrence:
South Africa (Western Cape)
Additional data:
Estimated area of occupancy (AOO) - km2:196
Continuing decline in extent of occurrence (EOO):Yes
Number of Locations:16
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:There are large subpopulations (possibly more than 1,000 mature individuals) in the Oudste, Thee, Noordhoeks, Boskloof, Heks (including the mainstream Olifants nearby), Rondegat, Jan Dissels, Dwars, Breekkrans and Krom tributaries and smaller populations (possibly less than 1,000 mature individuals) in the Ratel, Boontjies, Biedouw, Tra Tra, Eselbank and Matjies tributaries (Bills 1999).
Current Population Trend:Stable
Additional data:
Population severely fragmented:No
No. of subpopulations:16

Habitat and Ecology [top]

Habitat and Ecology:The species is common and widespread in both the lower and headwater sections of perennial streams and appears to prefer larger pools and deeper water. The species inhabits cobble riffles as juveniles but as they mature they are found in a wide variety of habitats such as deeper runs and pools (Bills and Impson 2013). They are more active during night hours and hide in crevices during the day, which allows some adults to co-exist with alien predatory fish such as Bass (Micropterus spp.) in some habitats. Electrofishing and snorkeling indicate that they use holes in the banks, crevices under rocks and vegetation root stocks as refuges. It was also found in deep pools in the Tra Tra and Biedouw Rivers (4-5 m depth) (Bills and Impson 2013). The species is carnivorous, feeding primarily on aquatic insects such as Caddisfly larvae (Skelton 2001).
Continuing decline in area, extent and/or quality of habitat:Yes

Use and Trade [top]

Use and Trade: This small species is not a target of subsistence or recreational anglers, and is not kept in aquaria, except for public awareness purposes under permit.

Threats [top]

Major Threat(s): The introduction of alien fishes, particularly Smallmouth Bass (Micropterus dolomieu) into the Olifants-Doring River System (ODRS) in the 1940s, probably caused a major reduction in their range and numbers in mainstem habitats. Since then, the decline due to alien fish predation and competition has reduced due to the inability of Smallmouth Bass and Spotted Bass (Micropterus punctulatus) to move above some barriers in tributary streams. Currently, the cobble habitat found in the tributaries are their preferred habitat, where in some streams they co-exist with alien invasive Bass species. There appears to be an interaction between the amount of sand cover over cobbles (exacerbated in rivers in heavily farmed areas) and vulnerability to impacts from Micropterus spp. (Woodford et al. 2005). Further research is required to assess the specific impacts of invasive alien fish, currently there is evidence that it has negative impacts on the abundance of Austroglanis gilli. Large parts of the ODRS, especially the fertile river valleys are heavily farmed for citrus. Unsustainable water abstraction for irrigation purposes during the hot dry season (November to March) is a major threat that affects the middle to lower reaches of almost all the tributary streams as well as most mainstream areas. Rates of abstraction are usually so severe it stops river flow, resulting in habitats being reduced to warm shallow pools that are not the preferred habitat of this species. The effect of insecticides has not been quantified, but could have an increasing impact in the future as more orchards are being established (Bills 1999).

Conservation Actions [top]

Conservation Actions: In 2012 and 2013, about 4 km of the Rondegat River in the ODRS was successfully treated with rotenone to remove invasive Smallmouth Bass (M. dolomieu) which has led to substantial recoveries of several threatened fish species (Weyl et al. 2014) and this should also lead to increases in the population size in that section of the river. Further rotenone treatments are planned for the Biedouw and Breekkrans Rivers to remove Bass species (Micropterus spp.) and this is expected to increase population sizes of Austroglanis gilli and several threatened cyprinid species. In the Thee River of the ODRS, invasive Spotted Bass (Micropterus punctulatus) were successfully removed using mechanical methods between 2010 and 2014 from a 5 km stretch of the lower river which should benefit A. gilli. Five of the 16 locations for the species are partly in formal conservation areas (for example Cederberg Wilderness Area). In addition, Impson and Bills (2013) have prepared a conservation plan for the Catfishes (Austroglanis spp.) of the ODRS. This details actions needed to more effectively conserve these species. Recently, a report has been written by the conservation authority CapeNature on the priority rivers for fish conservation in the ODRS, which includes management actions required for effective protection of its habitat (Impson et al. 2016)

Citation: Van der Walt, R., Jordaan, M., Bills, R. & Impson, D. 2017. Austroglanis gilli. The IUCN Red List of Threatened Species 2017: e.T2427A99448983. . Downloaded on 20 September 2018.
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