An analysis of Nigerian freshwater fishes: those under threat and conservation options
Olaosebikan, B.D. and Bankole, N.O. (2005) An analysis of Nigerian freshwater fishes: those under threat and conservation options. In: 19th Annual Conference of the Fisheries Society of Nigeria (FISON) , 29 Nov - 03 Dec 2004 ,Ilorin, Nigeria, pp. 754-762.
Pollution Most of the fish species from Niger Delta are in one way or the other
threathened by pollution. The mangrove of the Niger Delta (7,292km2) is the least studied in the
world (Wilcox & Powell, 1985). It is even adjudged to be the largest mangrove stand in Africa
(Kinako, 1977). The mangrove swamp and the freshwater swamp forests of the coastal region of
Nigeria are estimated at 28,000km2 (Edwards, 1986). These ecosystems have been seriously
impacted by human activities in the past twenty-five years. It is even adjudged to be the largest
mangrove stand in Africa (Kinako, 1977). The mangrove swamp and the freshwater swamp
forests of the coastal region of Nigeria are estimated at 28,000km2 (Edwards, 1986). These
ecosystems have been seriously impacted by human activities in the past twenty-five years.
There. are more than 32 species of killies found in Nigeria; of these twenty occur in the mangrove
swamps and freshwater forests of the south. Of these twenty, eight are endemic to the
Delta. (Aphyosernion deltaense, Fundulopanchax sjoestedti, F. amo/di, F. filamentosum,
Epipiatys blafranus, E. longiventralis, Micropanchax scheeli, Foerschichthys nigeriensis). Killifish
being small and of little value to the local communities presently, can easily become extinct
without being noticed. These fish lives in habitats like weedy parts of streams, rivers, swamps,
marshes and seasonal/ temporary pools that are easily affected by environmental perturbation.
In Nigeria, the threat of oil pollution started in the 70s when between 1972 and 1980, 836
oil spill incidents were recorded resulting in 1,405,406 barrels of oil polluting the environment.
Between January and May 1981 alone, 121 spills were recorded (Awobajor 1981). Within twentythree
years the rate of oil spillage has assumed an alarming proportion as a result of increase in
oil exploration, illegal bunkering, vandalization and ethnic unrest in the Niger Delta. Presently it is
impossible to keep record of the spills except for large scale ones that are publicized in the
newspapers. To worsen the problem very little ecological impact assessments are conducted
when spillage occurs, most work are either sponsored by the affected communities or the oil
company involved in order to get or give compensation as the case may be. Such reports are
either distorted to favor those concerned or in most cases classified as secret, thus becoming
inaccessible to scientific scrutiny. One of the few studies that was done in depth is the Oshika
spill of 1983. It was reported that only fish with air breathing organs were found seven months
after the spillage while non-air-breathers that did not survive include Hemichrotnis, Thysochromis,
Mormyrids, Hepsetus, Alestes, Neolabias, several typrinodonts and Polycentropsis (Powell,
1986). It is known that crude oil contain toxic compounds like aromatic and naphtheno-aromatic
hydrocarbons while those that are not toxic form films on the water surface. on soil and the body
of the plants and animals. This results in serious asphyxiation and for such soil spawners like the
Fundulopanchax it meant mass mortality for both the eggs that have been deposited in the
substratum and the spawners. This definitely leads to reduce recruitment when there are
survivors or total extermination of the species in such habitat.
Surprisingly, the 1996, IUCN (International Union for Conservation of Nature) Red list of
endangered species does not include any Nigerian Freshwater species, Does it mean none of
them is on the verge of extinction considering the rate of habitat degradation as a result of
increase in human activities, population and poverty in the past 30 years of oil boom and doom.