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Freshwater fish in South Africa: what you need to know about their plight

The hidden struggle of South Africas freshwater fish

South Africa is home to a rich diversity of freshwater fish, many of which are endemic and endangered. However, these fish are facing a range of threats that jeopardize their survival and the ecosystem services they provide. In this article, we will explore some of the challenges and solutions for conserving South Africas freshwater fish.

The hidden struggle of South Africa’s freshwater fish

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What are the threats to freshwater fish in South Africa?

According to the World Wildlife Fund (WWF), freshwater biodiversity is declining at twice the rate of that in the oceans or forests, and about a third of freshwater fish species globally are threatened with extinction. In South Africa, some of the main threats to freshwater fish include:

  • Invasive alien species: Predatory fish such as bass, carp, and tilapia have been introduced to many rivers and dams for recreational fishing or aquaculture, but they have negative impacts on native fish by competing for food and habitat, spreading diseases, and preying on them. For example, the Clanwilliam sandfish, a migratory fish that spawns in the tributaries of the Doring River, has been decimated by bass that eat its juveniles.

  • Habitat degradation and fragmentation: Human activities such as agriculture, mining, urbanization, and dam construction have altered the natural flow regimes, water quality, and connectivity of rivers and wetlands. This affects the availability and suitability of habitats for freshwater fish, especially those that require specific conditions for spawning or migration. For instance, the Clanwilliam sawfin, a large cyprinid that used to inhabit most of the Cederberg rivers, has been reduced to 11 isolated populations due to dams blocking its movements.

  • Overexploitation: Freshwater fish are an important source of food and income for many rural communities in South Africa, but they are often harvested unsustainably by illegal or unregulated fishing methods such as gill nets, traps, spears, and poisons. This reduces the abundance and diversity of fish stocks and affects their reproductive potential. For example, the Olifants River system has lost several endemic fish species due to overfishing.

  • Climate change: Climate change is expected to exacerbate the existing threats to freshwater fish by altering the temperature, precipitation, and evaporation patterns that influence river flows and water levels. This may result in more frequent droughts or floods that affect the survival and distribution of freshwater fish. For example, higher water temperatures may favour invasive alien species over native ones or reduce the dissolved oxygen levels that fish need to breathe.

What are the conservation efforts for freshwater fish in South Africa?

Despite the bleak situation, there are some hopeful signs of conservation action for freshwater fish in South Africa. Some of the initiatives and projects that are underway or planned include:

  • Alien fish eradication: One of the most successful examples of alien fish removal is the Rondegat River project, which cleared four kilometres of stream from invasive bass using a chemical called rotenone, and restored the habitat for native fish such as the Clanwilliam yellowfish and the Clanwilliam redfin. Similar projects are planned or in progress for other rivers in the Cape Fold Ecoregion, such as the Biedouw and Oorlogskloof, to protect the sandfish and other endemic species.

  • Freshwater fish rescue: Another innovative approach to save the sandfish is the Saving Sandfish project, which involves collecting juvenile sandfish from the Biedouw River before they are eaten by bass, and rearing them in temporary nurseries in dams cleared of alien species. Once they grow large enough to avoid predation, they are released back into the river or translocated to other suitable habitats. The project aims to rescue 5\u2009000 sandfish by the end of 2022.

  • Freshwater biodiversity information system: The Freshwater Biodiversity Information System (FBIS) is an online platform that provides access to reliable and comprehensive data on freshwater biodiversity in South Africa. The FBIS integrates data from various sources, such as museum collections, citizen science, environmental impact assessments, and research projects, and allows users to visualize, analyze, and download data for various purposes. The FBIS supports national freshwater fish conservation decisions by informing species assessments, conservation planning, monitoring, and reporting.

  • Freshwater protected areas: Freshwater protected areas are designated areas that aim to conserve freshwater biodiversity and ecosystem services by regulating or prohibiting activities that may harm them. South Africa has several types of freshwater protected areas, such as national parks, nature reserves, wetlands of international importance (Ramsar sites), and freshwater ecosystem priority areas. However, these areas cover only a small fraction of the countrys freshwater ecosystems and need to be expanded and effectively managed to ensure long-term conservation outcomes.

Why are freshwater fish important in South Africa?

Freshwater fish are not only valuable for their ecological role and intrinsic worth, but also for their social and economic benefits to South Africa. Some of the reasons why freshwater fish are important include:

  • Food security and livelihoods: Freshwater fish are an important source of protein and income for many rural and coastal communities in South Africa, especially those who depend on subsistence or small-scale fisheries. According to the Department of Agriculture, Forestry and Fisheries, about 140 000 people are directly or indirectly employed by the fisheries sector. Freshwater fish also contribute to the national economy through commercial fisheries, aquaculture, and trade.

  • Biodiversity and ecosystem services: Freshwater fish are part of the rich diversity of life that inhabits South Africa's rivers, lakes, and wetlands. Many of these fish species are endemic, meaning they occur nowhere else in the world, and some are threatened with extinction. Freshwater fish also provide various ecosystem services, such as nutrient cycling, water purification, sediment transport, and food web support. By conserving freshwater fish, we also protect the health and functioning of freshwater ecosystems.

  • Cultural and recreational value: Freshwater fish have cultural and recreational value for many South Africans, who enjoy fishing as a hobby, sport, or tradition. Fishing can also provide educational and tourism opportunities, as well as social and psychological benefits. Some freshwater fish species have cultural or spiritual significance for certain groups of people, such as the sacred catfish of the Limpopo River.



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