Observations on the food and feeding habits of the African electric catfish Malapterurus electricus (Gmelin)

The diet and feeding habits of the African electric catfish Malapterurus electricus in their natural habitat in Lake Kainji, and in the River Niger, downstream of Kainji dam, Nigeria, have been described and compared. The study showed the electric catfish is a voracious piscivore. It feeds on cichlids, clupeids, schilbeids and other available fish species. From the size distribution, numbers and composition of the small prey fish species examined in electric catfish stomachs, it was inferred that the powerful high-frequency electric organ discharge volleys serve as major predatory mechanism.     

Food and feeding of the mormyrid fishes of Lake Kainji, Nigeria, with special reference to seasonal variation and interspecific differences

The feeding habits of mormyrids from Lake Kainji, Nigeria, are discussed in relation to the decreased abundance of these fish since impoundment in 1968. Evidence is presented of both intra-specific seasonal variation in diet and inter-specific trophic divergence. These variable factors are discussed in relation to the degree of success achieved by certain species in the lake.     

The macrophytic vegetation of the draw-down area of Lake Kainji, Nigeria

Recent publications on the vegetation of Lake Kainji, Nigeria, give the impression that Echinochloa pyramidalis is the dominant macrophyte species of the lake. However, our experience of working on the lake since 1979 suggests a different floristic composition of the macrophyte vegetation of the lake. The most frequent macrophyte in Lake Kainji is Echinochloa stagnina. At all sites investigated, emergent macrophytes are more important than floating macrophytes. There is a possible successional shift from an Echinochloa pyramidalis sere to an Echinochloa stagnina stage. This argument does not, however, preclude the possibility of a mis-identification by early workers.     

Dual phylogenetic origins of Nigerian lions (Panthera leo)

Lion fecal DNA extracts from four individuals each from Yankari Game Reserve and Kainji‐Lake National Park (central northeast and west Nigeria, respectively) were Sanger‐sequenced for the mitochondrial cytochrome b gene. The sequences were aligned against 61 lion reference sequences from other parts of Africa and India. The sequence data were analyzed further for the construction of phylogenetic trees using the maximum‐likelihood approach to depict phylogenetic patterns of distribution among sequences. Our results show that Nigerian lions grouped together with lions from West and Central Africa. At the smaller geographical scale, lions from Kainji‐Lake National Park in western Nigeria grouped with lions from Benin (located west of Nigeria), whereas lions from Yankari Game Reserve in central northeastern Nigeria grouped with the lion populations in Cameroon (located east of Nigeria). The finding that the two remaining lion populations in Nigeria have different phylogenetic origins is an important aspect to consider in future decisions regarding management and conservation of rapidly shrinking lion populations in West Africa.     

Food and feeding of three Distichodus species (Pisces: Characiformes) in Lake Kainji,Nigeria

The food and feeding of three Distichodus species in Lake Kainji, Nigeria was studied. Sixty 140 and 528 specimens of Distichodus brevipinnis, D. engycephalus and D. rostratus respectively were examined. All three species were exclusively herbivorous. Their feeding was intense in the evening until dusk but declined during the day. All exhibited some seasonal variation in their food preferences.     

Notes and Records

Gastro intestinal helminths and food of the African hedgehog Atelexia albiventris (Wagna) in the Kainji Lake area of Nigeria     

Notes and Records

Variation in activities of Senegal kob (Kobus kob kob Erxleben 1777) during daylight period in an enclosure at Kainji Lake Research Institute range farm, New Busa, Nigeria     

Haematology and habits in catfish of the genus Synodontis

African catfish of the genus Synodontis vary in their habits, from inverted plankton eaters to normally oriented benthos eaters. Haemoglobin concentrations and red cell counts vary between populations of one species, and between species of differing habits. Synodontis schall from the well-aerated White Nile had lower haemoglobin concentrations than members of the same species from Lake Kainji, Nigeria. Synodontis membranaceus , an inverted plankton eater, had lower haemoglobin concentrations than the bottom dwelling S. filamentosus and S. nigrita. Species with intermediate habits, such as S. batensoda and S. ocellifer had intermediate concentrations of haemoglobin.
It is suggested that these differences in haemoglobin concentration are a result of differing habits. Those species that enter poorly aerated water are stimulated to make more haemoglobin.     

The food and feeding habits of Hydrocynus forskahlii Cuvier and Hydrocynus brevis Günther in Lake Kainji, Nigeria

The diets and modes of feeding of Hydrocynus forskahlii Cuvier and Hydrocynus brevis Günther are described. Both species are mainly piscivorous in Lake Kainji. H. forskahlii feeds largely upon small clupeids though very large specimens prey more heavily upon the characid Alestes baremose. H. brevis preys upon a wide variety of species by swallowing them whole but also attacks large fish and bites pieces from them. Sexual dimorphism in H. brevis is described. The effects of predation upon the fish stock of Lake Kainji by Hydrocynus species are discussed.     

The use of opercular bones in the study of age and growth in Labeo senegalensis from Lake Kainji, Nigeria

Check marks were found on the scales and opercular bones of Labeo senegalensis from Lake Kainji, Nigeria. The scale marks were often indistinct and difficult to interpret, but an attempt was made to determine age from the opercular bones.
At least two check marks per year were found on the opercular bones, one of these occurring during June-July, and the other during January. The relationship between opercular length and fish total length was plotted logarithmically and back-calculations of length made.
Problems of interpretation are discussed in relation to possible causes of ring formation.     

Seasonal variation in the protein content and the grazing of some tropical savanna grasses

This paper presents the effects of seasonal variation on the protein contents of four grass species examined in the experimental fire plots at Kainji Lake National Park in the Northern Guinea savanna zone of Nigeria. Also reported is the proportion of grass utilized on year-long basis. Tropical savanna grasses generally have higher protein contents at the beginning of the growing season than at the end when they become tall, coarse and unpalatable. It is also shown that the percentage of grass species utilized by game follow the seasonal changes in their protein contents; utilization being highest when the protein content of grass is optimum. It is stressed that trees, shrubs and forbs should not be totally eliminated from grazing lands because of the great contribution they make to animal feeding during the dry season when the grasses become dry and coarse with low nutritive value.     

Individual Identification and Genetic Variation of Lions (Panthera leo) from Two Protected Areas in Nigeria

This survey was conducted in two protected areas in Nigeria to genetically identify individual lions and to determine the genetic variation within and between the populations. We used faecal sample DNA, a non-invasive alternative to the risky and laborious task of taking samples directly from the animals, often preceded by catching and immobilization. Data collection in Yankari Game Reserve (YGR) spanned through a period of five years (2008 –2012), whereas data in Kainji Lake National Park (KLNP) was gathered for a period of three years (2009, 2010 and 2012). We identified a minimum of eight individuals (2 males, 3 females, 3 unknown) from YGR and a minimum of ten individuals (7 males, 3 females) from KLNP. The two populations were found to be genetically distinct as shown by the relatively high fixation index (F_ST  = 0.17) with each population exhibiting signs of inbreeding (YGR F_IS  = 0.49, KLNP F_IS  = 0.38). The genetic differentiation between the Yankari and Kainji lions is assumed to result from large spatial geographic distance and physical barriers reducing gene flow between these two remaining wild lion populations in Nigeria. To mitigate the probable inbreeding depression in the lion populations within Nigeria it might be important to transfer lions between parks or reserves or to reintroduce lions from the zoos back to the wild.     

Observations on meristic characters separating Pellonula afzeliusi Johnels, 1954 from Sierrathrissa leonensis Thys Van den Audernaerde, 1969

The meristic features of Pellonula afzeliusi and Sierrathrissa leonensis are compared to remove the confusion that has arisen over the identity of two clupeid species in West African freshwaters.
The discovery of a breeding population of S. leonensis in Kainji Lake confirms that it is correct to regard S. leonensis as a separate species and not the young of either Pellonula or Cynothrissa as was claimed by Roberts (1972).     

Notes on the biology of the mayfly Povilla adusta in West Africa

A study of the mayfly Povilla adusta Navas in five West African lakes showed at least one population (in Barombi Mbo) with a clear lunar periodicity of emergence, and at least one without, at Kainji Lake. The seasonal distribution of Povilla eggs in fish stomachs at Kainji implies a delayed effect of lake level on adult numbers. The relatively small size and short generation time (probably three months) of Povilla in Barombi Mbo, by comparison with the same species in Lake Victoria, may be related to the higher temperature of Barombi Mbo. The eggs of bdelloid rotifers were found attached to Povilla larvae from some of the lakes.     

The food of adult copepods from Lake Kainji, Nigeria

SUMMARY. Gut contents of adult copepods from Lake Kainji were analysed. The calanoid copepod Tropodiaptomus banforanus was exclusively herbivorous with Melosira and Peridinium forming a large proportion of the diet. Of the cyclopoid copepods, Mesocyclops leuckarti was mainly carnivorous while the smaller Thermocyclops neglectus was mainly herbivorous. Experiments with Diplocystis (Microcystis) showed that it was not ingested by these three copepod species even after starvation and possible explanations for the results are discussed.     

The effect of the impoundment of Lake Kainji, Nigeria, on the indigenous species of mormyrid fishes

SUMMARY. Changes in the numbers and species composition of mormyrid fishes since the impoundment of the Niger (Lake Kainji) are analysed. An initial decline after impoundment appears to have been reversed and these fish are now increasing. The increase is, however, restricted to a few species only; many forms common in the river are still declining or have disappeared altogether. Marked seasonal variations in abundance are described and possible explanations discussed.     

The buoyancy and orientation of the upside-down catfishes of the genus Synodontis (Pisces: Siluroidei)

The forces involved in the buoyancy of the genus Synodontis are unusually large owing to the well-developed cephalo-nuchal shield possessed by all members of the genus, and the large swim bladder and high levels of body fat needed to counteract this. A new method of determining the quantity of crude lipid in the tissues was developed and tested against a recognized method. Negative correlations were found between the total quantities of fat present and the volumes of the swim bladder for several species. Two species which maintained neutral buoyancy but occupied different ecological niches were found to achieve neutrality by different means, one possessing an abnormally large swim bladder and the other very large quantities of fat. The amount of bone present was found to be considerably greater than in species from other genera.
Several species of this genus regularly invert and swim on their backs. Three of the species known to do this were found amongst the 16 species present in the man-made Lake Kainji on the River Niger in Nigeria. The orientations of many of the species were studied both under natural conditions and in the laboratory. Several possible causes of inversion were investigated, including both physical and behavioural factors. The position of the food source was found to be the most important factor controlling the orientation of the species. By manipulating this it was possible to persuade normally orientating species to invert, and inverting species to return to normal orientation. Three theories to explain the inverting habit are advanced and their merits discussed.     

The food and feeding habits of Eutropius niloticus (Ruppell), family Schilbeidae (Osteichthyes: Siluriformes) in Lake Kainji,Nigeria

Studies on the food and feeding habits of Eutropius niloticus in Lake Kainji, Nigeria revealed that the fish is omnivorous but fed more on insects than on any other food. The most important insects were Povilla adusta Navas nymphs and imagos and adults of the common grasshoppers. Fish, particularly the clupeids Sierrathrissa leonensis Thys Van den Audernaerde and Pellonula afzeliusi Johnels, also formed an important part of the diet. There was seasonal variation of organisms selected for food and there were variations in the dietary items selected by different age groups. Accumulation of fat was found to correlate with seasonal feeding intensity. E. niloticus serves as food for other fishes.     

The vegetation of the Kainji reservoir site in Northern Nigeria

The Federal Government of Nigeria is constructing a dam across the River Niger at Kainji (9°51N, 4°37E). When complete approximately 130,000 hectares will be inundated. An account of the climate, hydrology, geology, pedology, land-usage and vegetation of the reservoir site is given. The terrestrial plant communities are described in outline. The aquatic and marsh plant communities are described in more detail using the floristic-ecological method.     

Sex,reproductive cycle and variations in the fecundity of the family schilbeidae (Osteichthyes : Siluriformes) in Lake Kainji,Nigeria.

The sex, reproductive cycle and variations in the fecundity of the family Schilbeidae (Osteichthyes : Siluriformes) in Lake Kainji, were investigated. Sexual differences in size and morphology were found to exist in all species. Sex ratio varied with species and season. There were more females than males in the population. Size at maturity varied from species to species with the males attaining maturity at a slightly lower length than the females. Breeding condition was attained mainly during the rains in Eutropius niloticus, Schilbe mystus and Siluranodon auritus and in the dry and rainy seasons in Physailia pellucida. Spawning occurred once during the breeding season in E. niloticus and S. mystus; and more than once during the prolonged breeding season in P. pellucida. Condition factors did not show any correlation with maturation of gonads. Fecundity was found to vary from species to species.