A rice-fish culture experiment was conducted to determine the effects of different fertilizer treatments on water quality parameters, i.e. dissolved oxygen, temperature, pH and conductivity, as well as the nutrients nitrogen, potassium and phosphorus. Data gathered were subjected to analysis of variance. Dissolved oxygen, nitrogen and potassium concentrations showed significant differences (P<0.5) among the various rice-cum-fish management systems, with the highest mean concentration in the fish-only management system. The insignificant difference (P>0.05) in the oxygen concentration between rice-only and rice-cum-fish management systems was probably due to the narrow spacing of rice cultivars (20 · 20 cm). Under different fertilizer treatments, dissolved oxygen, nitrogen and potassium concentrations were not significantly different (P>0.05), indicating that different fertilizer treatments had no effect on their concentrations. Mean temperature, pH, conductivity and phosphorus concentrations in all rice-cum-fish management systems and fertilizer treatments did not differ significantly (P>0.05) from each other. This might possibly be due to the hydrogeology and climatic conditions of the area. However, all levels of studied water quality parameters were tolerable to the fish (Oreochromis niloticus) in the rice-fish ecosystem. There was no significant difference (P>0.05) in rice yield between the rice-fish management system and the rice-only management system. However, there was a significant difference (P<0.05) under different fertilizer treatments, with nitrogen/phosphorus/potassium (NPK) (20 : 10 : 10) giving the highest production of an estimated 14.36 kg ha )1 year )1 , indicating that fertilizer treatments had an effect on the rice yield. Fish growth was not significantly different (P>0.05) under different rice-fish management systems, but was significant (P<0.05) under different fertilizer treatments. Chicken manure gave the best growth with 17.7±5.97 g; estimated fish yields were 343 and 602 kg ha )1 year )1 in fish monoculture and rice-fish culture respectively. It is recommended that farmers who are more inclined to fish or rice production in integrated rice-cum-fish management systems could use chicken manure and NPK (20 : 10 : 10) respectively.

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Population dynamics and life-history traits of two sympatric nothobranchiid killifishes, Epiplatys bifasciatus and E. spilargyreius,were studied for 24 months in an intermittent stream in the Kainji Lake Basin, Nigeria. Epiplatys bifasciatus was more abundant throughout the study period, but monthly abundance of both species followed the same pattern. For both species, growth parameters and life-history strategies are characterised by small size, high growth rate, early maturity, high reproductive effort through daily spawning, short generation time, short life span and high mortality rate. Both species reproduce throughout the year, with peak periods of recruitment during the February to April and October to November periods. The population structures showed a preponderance of females over males, while males attained a larger total length than females. Three habitat types (vegetated pool, vegetated riffle, and marsh) were preferred by both species, whilst unvegetated habitats were avoided. Epiplatys spilargyreius was fairly specific in its habitat preference, with a significant positive correlation (r = 0.65, p < 0.05) to marshy habitat, whereas E. bifasciatus showed some habitat-use plasticity.

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Effect of environmental variables on the population dynamics of two sympatric notobranchiid fishes, Epiplatys bifasciatus and E. spilargyreius in the seasonal Monai Stream of the Kainji Lake Basin in Nigeria were studied for 24 months. In all, 2,544 and 937 specimens of E. bifasciatus and E. spilargyreius were collected respectively. E. bifasciatus was more abundant of the two species throughout the study period. For both species, monthly abundance followed the same pattern; May to October (rainy season) was a period of low abundance while November to April (dry season) was a period of high abundance. Relative abundance was correlated with physical, chemical, and biological factors using regression analyses. The relationship between 12 environmental variables (temperature, transparency, conductivity, hydrology, dissolved oxygen, pH, nitrogen, phosphate, potassium, sodium, CaCO 3 , chlorine) and abundance of the two species showed that E. spilargyreius abundance was strongly correlated with water conductivity (Pearson's coefficient, r = 0.884, P<0.01) but correlated negatively with temperature (Pearson's coefficient, r =-0.559 at P< 0.05). E. bifasciatus abundance had a slight positive correlation with alkalinity (r = 0.501 at P< 0.05). Three habitat types (vegetated pool, vegetated riffle, and marsh) were preferred by both species, whilst unvegetated habitats were avoided. E. spilargyreius was fairly specific in its habitat preference, with a significant positive correlation (r = 0.65, P < 0.05) to marshy habitat, whereas E. bifasciatus showed some flexibility in habitat-use.