Hydrocynus vittatus, the African Tigerfish or Tiervis or Ndweshi^[2] is a predatory freshwater fish distributed throughout much of Africa.

Distribution

This species distribution covers the Niger/Bénoué, Ouémé River, Senegal River, Nile, Omo River, Congo River, Lufira, Lualaba River, Luapula, Zambezi, Limpopo River, Rovuma, Shire River, Rufiji River, Ruaha, Wami River, and Ruvu River; as well as Lakes - Lake Bangweulu, Moéro, Tanganyika, Upemba, Rukwa and Malagarazi. It is also found in the Okavango Basin and lower reaches of coastal systems south to the Pongola River and in man-made Lake Kariba^[3].

Habitat and Ecology

A demersal, migratory freshwater species, Hydrocynus vittatus prefers warm, well-oxygenated water, mainly in larger rivers and lakes. The smaller individuals form roving schools of like-sized fish; aptly described as fierce and voracious but very large specimens may be solitary. It preys on most abundant fish species available but sepies of the genera Brycinus, Micralestes, Barbus, and Limnothrissa are favoured prey. Breeding occurs on a few days each year, when the initial rains have swollen the rivers and streams, normally in December and January when a spawning migration is undertaken upstream into rivers and smaller streams. The females spawn a great number of eggs in very shallow water, among the stems submerged and partly submerged vegetation where the fry stay until thereceding of the flood water makes them return to the main channels.^[1]

Population and Conservation Status

This species is common and widespread over most of its range. In the most studies population, that of Lake Kariba on the Middle Zambezi River, the population fluctuated markedly, apparently in direct relation to the abundance of the introduced clupeid Limnothrissa miodon which forms a major part of its diet. There is a commercial fishery in Lake Rukwa, where it forms about 3.9% of the yield.

Hydrocynus vittatus have declined in some river systems in southern Africa as a result of pollution, water abstraction and obstructions by dams and weirs that prevent migration. It is locally threatened by unregulated gillnet fisheries. In east Africa, threats to populations include overfishing, reductions in water quality due to agricultural activities and deforestation, and pesticide pollution.^[1]

References