Tilapia Guinasana.Pdf

The IUCN Red List of Threatened Species™ ISSN 2307-8235 (online) IUCN 2008: T63354A12662434

Tilapia guinasana

Assessment by: Bills, R.

View on www.iucnredlist.org

Citation: Bills, R. 2007. Tilapia guinasana. The IUCN Red List of Threatened Species 2007: e.T63354A12662434. http://dx.doi.org/10.2305/IUCN.UK.2007.RLTS.T63354A12662434.en

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THE IUCN RED LIST OF THREATENED SPECIES™ Taxonomy

Kingdom Phylum Class Order Family

Animalia Chordata Actinopterygii Perciformes Cichlidae

Taxon Name: Tilapia guinasana Trewavas, 1936 Assessment Information

Red List Category & Criteria: Critically Endangered B1ab(iii)+2ab(iii) ver 3.1

Year Published: 2007

Date Assessed: March 1, 2007

Justification: Naturally occurs in a single location (Lake Guineas). Benign introductions have been made into Lake Otjikoto and other farm dams but these have no formal protection. Two major threats are ground water extraction and the introduction of alien fishes (primarily tilapiine cichlids). Impacts of tilapiines range from competition for food and space, predation to introgression. This species is assessed as Critically Endangered under criterion B as it has a highly restricted AOO <1 km² (the lake is only 50 m in diameter), is limited to a single location, and is threatened by ongoing groundwater extraction and the potential introduction of an alien species.

Previously Published Red List Assessments 1996 – Critically Endangered (CR)

1994 – Endangered (E)

1990 – Endangered (E)

1988 – Endangered (E)

Geographic Range

Range Description: Naturally occurs only in Lake Guinas, central Namibia. Benign introductions to Lake Otjikoto and several nearby farm dams (Skelton 1987, 2001).

Country Occurrence: Native: Namibia

Habitat and Ecology (see Appendix for additional information) Sink hole lake, substrate is rocky ledges. Depth range is broad; observed breeding down to 67 m.

Systems: Freshwater

Threats (see Appendix for additional information) Two major threats are extraction of groundwater for farming and the potential for introducing alien tilapiines. Oreochromis mossambicus is the largest threat as it is presently in Lake Otjikoto and, if introduced, it thought likely to directly compete for food and space and possibly act as a predator. There is also a potential threat of introgression from the introduction of T. sparrmanii which is known to interbreed with T. guinasana and produce fertile offspring.

Conservation Actions (see Appendix for additional information) Control of ground water use by water management authorities is essential. The movement of fishes around Namibia in general and introductions into isolated sink holes specifically must be prevented by nature conservation authorities. Programmes for controlling alien fishes should be considered. Possibly additional benign introductions should be considered. Credits

Assessor(s): Bills, R.

Reviewer(s): Snoeks, J. (Freshwater Fish Red List Authority) & Darwall, W. (Freshwater Biodiversity Assessment Unit)

© The IUCN Red List of Threatened Species: Tilapia guinasana – published in 2007. 3 http://dx.doi.org/10.2305/IUCN.UK.2007.RLTS.T63354A12662434.en Bibliography Groombridge, B. (ed.). 1994. 1994 IUCN Red List of Threatened Animals. IUCN, Gland, Switzerland and Cambridge, UK.

IUCN. 1990. IUCN Red List of Threatened Animals. IUCN, Gland, Switzerland and Cambridge, UK.

IUCN. 2007. 2007 IUCN Red List of Threatened Species. Available at: www.iucnredlist.org. (Accessed: 12th September 2007).

IUCN Conservation Monitoring Centre. 1988. IUCN Red List of Threatened Animals. IUCN, Gland, Switzerland and Cambridge, UK.

Skelton, P.H. 1987. South African Red Data Book - Fishes. South African National Scientific Programmes Report 137. Council for Scientific and Industrial Research, Pretoria.

Skelton, P.H. 2001. A Complete Guide to the Freshwater Fishes of Southern Africa. Struik Publishers, Cape Town, South Africa.

Citation Bills, R. 2007. Tilapia guinasana. The IUCN Red List of Threatened Species 2007: e.T63354A12662434. http://dx.doi.org/10.2305/IUCN.UK.2007.RLTS.T63354A12662434.en

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Habitats (http://www.iucnredlist.org/technical-documents/classification-schemes)

Major Season Suitability Habitat Importance? 5. Wetlands (inland) -> 5.18. Wetlands (inland) - Karst and Other - Suitable - Subterranean Hydrological Systems (inland)

Threats (http://www.iucnredlist.org/technical-documents/classification-schemes)

Threat Timing Scope Severity Impact Score 5. Biological resource use -> 5.4. Fishing & harvesting Future - - - aquatic resources -> 5.4.6. Motivation Unknown/Unrecorded Stresses: 2. Species Stresses -> 2.1. Species mortality 7. Natural system modifications -> 7.2. Dams & water Ongoing - - - management/use -> 7.2.8. Abstraction of ground water (unknown use) Stresses: 1. Ecosystem stresses -> 1.2. Ecosystem degradation 8. Invasive & other problematic species & genes -> Future - - - 8.1. Invasive non-native/alien species -> 8.1.2. Named species (Tilapia sparrmanii) Stresses: 2. Species Stresses -> 2.3. Indirect species effects -> 2.3.1. Hybridisation 8. Invasive & other problematic species & genes -> Future - - - 8.1. Invasive non-native/alien species -> 8.1.2. Named species (Oreochromis mossambicus) Stresses: 2. Species Stresses -> 2.1. Species mortality 2. Species Stresses -> 2.3. Indirect species effects -> 2.3.2. Competition

Conservation Actions Needed (http://www.iucnredlist.org/technical-documents/classification-schemes)

Conservation Actions Needed 2. Land/water management -> 2.1. Site/area management

3. Species management -> 3.2. Species recovery

3. Species management -> 3.3. Species re-introduction -> 3.3.2. Benign introduction

© The IUCN Red List of Threatened Species: Tilapia guinasana – published in 2007. 5 http://dx.doi.org/10.2305/IUCN.UK.2007.RLTS.T63354A12662434.en The IUCN Red List of Threatened Species™ ISSN 2307-8235 (online) IUCN 2008: T63354A12662434

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