The source of the Orange river is in Lesotho and that of the Vaal on the Mpumalanga highveld whereas their tributaries extend well into most provinces of South Africa as well as into Botswana and Namibia.
The Orange river eventually flows into the Atlantic Ocean at Oranjemund on the West coast border between South Africa and Namibia.
Attaining a mass of around 9 kg it is an opportunistic feeder, eating a variety of food types ranging from plant material to aquatic insects, crabs, shrimps and small fish.
The smallmouth yellowfish is a slow-growing species with a low egg-to-mass ratio (fecundity), only becoming sexually active at a fork length of 30 cm when it is almost seven years old.
When water temperatures exceed 19 °C in Spring, small shoals of fish migrate to shallow rocky areas to spawn and may do so intermittently from October to February.
The long spawning season is an adaptation to the food-driven river and ensures that yellowfish will be able to lay eggs whenever favourable conditions occur.
However, recent fish kills in the middle Vaal river and some tributaries are a cause for concern, as they have the potential to cause substantial damage to valuable recreational fisheries.
Whereas most of the ingredients of the effluent are not directly toxic to fish, the enriched water facilitates algal blooms that reduce dissolved oxygen concentration to lethal levels.
The recent explosion of grass carp in dams of the middle Vaal river is seen as a potentially serious threat as this prolific species grows to more than 20 kg and is an obvious competitor for food.
At present, each province straddling the Orange-Vaal catchment area has different policies regarding the capture of yellowfish which complicates law enforcement and angler awareness.
Bear in mind that conservancies can only be meaningful if participating land owners are made aware of river and fish issues and are guided in the implementation of relevant measures.
The aims are simple and include three basic conservation concepts: There is a considerable body of national and provincial legislation that enable authorities to respond to illegal activities on rivers such as pollution, netting, interfering with spawning fish, stocking of alien species and so on.
A major concern however is the current lack of capacity in nature conservation at provincial and national level to manage rivers and freshwater fish effectively.
The Free State Department of Tourism, Environmental and Economic Affairs provide smallmouth yellowfish for stocking of farm dams as an alternative to alien fish species.
This method is preferable to culturing/breeding yellowfish which can result in unwanted hybrids as well as fish with genetic material less than ideal for release into natural systems.