Overview

Distribution

Range Description

This subspecies is known from the Democratic Republic of Congo to Namibia and Botswana.

Central Africa: Serranochromis robustus jallae is known from the Luapula-Mweru system, from the Lualaba and from the Kasai.

Southern Africa: It is found in the upper Zambezi, Okavango, Kafue and Zambian Congo systems. Its native range in Zimbabwe is the Zambezi River above Victoria Falls although two specimens were taken in Lake Kariba in 1968 (Balon 1974) and some were stocked in 1975 (Kenmuir 1983). It has been widely translocated by anglers in Zimbabwe and could be expected in almost any river or impoundments on the central plateau.
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Ecology

Habitat

Zambezi River Demersal Habitat

This taxon is one of a number of demersal species in the Zambezi River system of southern Africa. Demersal river fish are found at the river bottom, feeding on benthos and zooplankton

Nutrient levels in the Zambezi River are relatively low, especially in the upper Zambezi; in that reach, above Victoria Falls, most of the catchment drains Kalahari sands, whose nutrient levels are inherently low due to their aeolian formation; moreover, agricultural fertilizer addition throughout the Zambezi watershed is low, due to the shortage of capital available to farmers of this region.

Nitrate levels (as nitrogen) in the upper Zambezi are typically in the range of .01 to .03 milligrams per liter. Correspondingly electrical conductivity of the upper Zambezi is on the order of 75 micro-S per centimeter, due to the paucity of ion content. From the Luangwa River downstream nitrate levels elevate to .10 to .18 milligrams per liter, and electrical conductivity rises to a range of two to four times the upper Zambezi levels. Not surprisingly, pH, calcium ion concentration, bicarbonate and electrical conductivity are all higher in portions of the catchment where limestone soils predominate compared to granite.

There are a total of 190 fish species present in the Zambezi River, including eel and shark taxa. The largest native demersal species present are the 117 centimeter (cm) long tiger fish (Hydrocynus vittatus), the 175 cm African mottled eel (Anguilla bengalensis labiata), the 120 cm Indonesian shortfin eel (Anguilla bicolor bicolor), the 200 cm Giant mottled eel (Anguilla marmorata), the 150 cm African longfin eel (Anguilla mossambica), the 183 cm Sampa (Heterobranchus longifilis), the 150 cm Cornish jack (Mormyrops anguilloides) and the 700 cm largetooth sawfish (Pristis microdon).

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Habitat and Ecology

Habitat and Ecology
Serranochromis robustus jallae is a demersal subspecies that mainly feeds on small fish, including squeakers (Synodontis spp.), insects and other small animals (Jackson 1961). Larger specimens prefer deeper water close to the bank, both in quiet water in eddies and also in strong current where the bank is being undercut. Smaller specimens are widespread including vegetation fringing the main channels,open and closed lagoons, and small tributaries (Skelton 2001; Tweddle et al. 2004). In its introduced range it occurs in streams and impoundments with varying characteristics. This subspecies incubates the eggs in the mouth. It breeds in summer, nesting along vegetated fringes of the mainstream. Winemiller (1991) classified the subspecies as a river-dwelling, epibenthic, diurnal piscivore.

Systems
  • Freshwater
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2010

Assessor/s
Marshall, B., Moelants, T. & Tweddle, D.

Reviewer/s
Snoeks, J., Tweddle, D., Getahun, A., Lalèyè, P., Paugy, D., Zaiss, R., Fishar, M.R.A & Brooks, E.

Contributor/s

Justification
Although there are localised threats, this subspecies has a wide distribution. It is therefore listed as Least Concern. It has also been assessed regionally as Least Concern for central and southern Africa.
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Population

Population
It is common and widespread.

Population Trend
Unknown
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Threats

Major Threats
Mining in the Katanga region for cobalt, copper, tin, uranium, dams and the use of toxic plants for fishing and overfishing form threats in this region. Artisanal, but very intensively diamond mining is a very important threat in small rivers in the Kasai region. The sand from digging in the river and the river beds causes sedimentation. Localised fishing effort depletes adult populations.
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Management

Conservation Actions

Conservation Actions
Since 2007 it has been prohibited to fish in Lake Mweru and the Luapula River on the Congolese site of the border. In Zambia, there is the Kasanka National Park around Lake Bangweulu. The fines didn’t work in this region. Even scientific collections were stopped. The government has burned 10,000 nets after measuring the nets. The governor (Morris Katunge) has paid the fishermen. Since 1st of May 2008, fishing was allowed again, but with controlled mesh sizes. The subspecies also has some protection in the Okavango Delta reserves.
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