“The Limpopo River has few fish species compared with other rivers in Africa (FAO 2004).” The low number of fish species found in the Limpopo River is attributed to the prolonged dry periods that characterise the region. These fluctuations impact streamflow and water temperature, making rivers challenging environments for sustaining fish populations. Relatively more fish species are found in the stable tributaries and dams (watercourses with consistent water presence) than in the main stem of the Limpopo River (FAO 2004).
There are at least 30 species found in the Limpopo River System of which cyprinids, catfish, Tilapia, trout and several brakish-water species (found in the estuary in Mozambique) provide a source of income and protein to the basin people living near these watercourses. These same species are suitable to aquaculture and can be stocked in dams. The Limpopo River Valley also supports a large number of mollusc species that can be harvested (Darwall et al. 2009).
Although an economic study of fisheries in the basin has yet to be done a number of individual studies in the basin countries have been completed and are outlined as follows from upstream to downstream. There is the potential for increased fisheries in the basin in all four countries (FAO 2004).
Fish Species of the Limpopo River
Ambassisspp., possibly three species in lower reaches;
Amphlius natalensis, in coastal areas;
Amphlius uranoscopus, in the lower reaches of the river;
Aplocheilichthys johnstoni; katangae; a variety of exotic poeciliids;
Austroglanis sclateri, translocated through the Orange-Vaal water transfer schemes;
Chiloglanis pretoriae, C. paratus, swierstrai;
Clarias gariepinus, C. ngamensis, theodorae;
Gambusia, an exotic species;
Glossogobius callidus, giurus in the lower reaches;
Lepomis macrochirus, an exotic species;
Micropterusspp., an introduced bass;
Mugilidae(mullet), numerous species in coastal areas;
Nothobranchius orthonotus, N. rachovii, furzeri in coastal areas;
Oncorhynchus mykiss, introduced exotic;
Oreochromis macrochir, translocated into parts of Zimbabwe from the Zambezi River system;
Oreochromis niloticus, an exotic species with a barred tail;
Oreochromis placidus, probably in lower river area;
Perca fluviatilis, an exotic species;
Psedocrenilabrus philander, a small cichlid;
Salmo trutta, brown trout;
Serranochromis meridianus, possible in lower reaches of the river;
Serranochromis thumbergi, introduced in parts of Zimbabwe from the Zambezi River system;
Synodontis zambezensis; an introduced exotic species;
Tilapia sparrmanii, rendalli, substrate-spawning tilapias.
Source: Bell-Cross and Minshull (1988); Lévêque, Bruton and Ssentongo (1988) in FAO 2004
Lepomis macrochirus is an exotic species found in the basin.
Source: Engbretson (no date)
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In South Africa, fish in the Limpopo River System are largely found in dams and the more stable tributaries feeding the main stem river. The frequency of occurrence of fish species is monitored at numerous sites in each of the Water Management Areas (WMAs) as part of the National Aquatic Ecosystem Health Monitoring Programme (NAEHMP) - River Health Programme (RHP). Fish are important indicators of river health, and their response to modified habitat and environmental conditions are measured as part of the Fish Response Assessment Index (FRAI). The FRAI looks at the baseline conditions and species as well as habitat preference and tolerance to change. A number of monitoring sites are found in the Limpopo WMA (69), Luvuvhu and Letaba WMA (43), Crocodile West and Marico WMA (98) and Olifants WMA (63).
Botswana and Zimbabwe
In Botswana and Zimbabwe, fisheries in the basin contribute little in the way of protein or economic benefits (FAO 2004) due to limited and variable streamflow in rivers.
Catch limit advisory at Inyankuni Dam, Zimbabwe.
Source: Schaefer 2010
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The lower Limpopo River is important to maintaining the productive brackish conditions at the river mouth in Mozambique (FAO 2004). The cultivation of marine species has only emerged in the last decade, and the brackish waters support a number of species that can serve as a source of income and protein to the people inhabiting the area (FAO 2004). In 2003 the aquaculture industry in Mozambique was producing marine shrimp (Penaeus spp.) and seaweed (Kappaphycus spp.) in commercial farms and Tilapia in artisanal farms (FAO 2005).
Alien Invasive Species and Fisheries
Fisheries in southern Africa are threatened by alien invasive fish species and by habitat degradation. In the Limpopo River Opsaridium peringueyi, Barbus rapax andChiloglanis swierstrai used to be more widely distributed but are now considered threatened. Rivers south of the Limpopo River also contain a large number of threatened species (IUCN 2009). Nile Tilapia (O. niloticus) is a notorious alien invasive species that has entered into, and outcompeted, species throughout southern Africa. In the Limpopo River system O. niloticus has replaced the less competitive tilapia species resident in dams in the basin- O. mossambicus. Micropterus and various other carp species are also impacting the fauna of the Limpopo River basin.