Materials and methodsThe physico-chemical properties of the Ogun River were recorded between January 1974 and December I975. A wet season with mean monthly rainfall of 9.72 cm. (s.d. = 5.07 cm) occurred from April through October, while a dry season with mean monthly rainfall of 0.56 cm. (s.d. = o.99 cm) occurred between November and March. The seasonal changes in the rainfall of the drainage area resulted in an alternation of the hydrological regimes of the river. The high water level of the river that arose as a result of the rains made the water flowed unidirectionally from July through December. After the rains, the water level receded gradually to a point where by January the river broke up into a chain of pools. In a lotic state, the water's tansparency, pH, total alkalinity and conductivity were lower, while its dissolved oxygen, free carbon dioxide concentrations were higher than the corresponding conditions in the residual pools formed when the water was lentic. In this latter form, the observed diurnal surface water temperature fluctuations were more and diel thermal stratification occurred. It was evident that the water in both phases was well aerated. The diurnal fluctuations in the water temperatures and the relationships between the determined environmental factors were assayed.

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Materials and methodsThe stomach contents of the fishes of the Upper Ogun River were scrutinised for three consecutive years. 8 out of the 36 species resident in the river are predominantly piscivorous. These are Mormyrops deliciosus, Hydrocynusforskahlii, Hepsetus odoe, Bagrus docmac, Lates niloticus and Hemichromisfasciatus. Piscivorous habits in Schilbe mystus and Eutropius niloticus are less developed. Three others, viz: Clarias lazera, Heterobranchus longifillis and Channa obscura, which were classified as piscivores by other workers, were caught. The stomachs of C. obscura examined were all empty while those of C. lazera and H. longifilis contained mainly aquatic invertebrates. The major prey of these piscivores are small sized Barbus spp. Other prey fishes include mormyrids, characids, cyprinids, citharinids, catfishes and cichlids. The relationships between the piscivorous and prey fishes and the partitioning of the available resources by these piscivores are discussed.

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Biochemical compositions (total protein = TP, total lipid = TL, globulin = Gl, albumin = Al and albumin/globulin = A/G ratio) of Oreochromis niloticus liver, kidney and brain exposed to 0.5 ppm aqueous extracts of Raphia vinifera (AERV) were investigated. The various biochemical compositions fluctuated with time of exposure to AERV. TP ranged between 0.91-4.64 mg/dl, Al between 0.41 -3.02 mg/dl, Gl between 0.70-3.40 mg/dl, A/G between 0.20-3.50 mg/dl and TL between 571.3-998.2 mg/dl. Significant (P<0.05) decrease in TP, Gl and TL values of the liver over either the brain or the kidney at 21-day duration in AERV, indicated high energy requirement for detoxification function of the liver. With these biochemical compositions in O. niloticus, it is inferred that their uses in the fish varied according to production in the tissue and relative effect of AERV, which produced fish's physiological dysfunction.