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Abstract:The effect of physical factors on fish species composition was studied during 12 months in Asa Lake, Nigeria. Fish and water samples were collected bimonthly (March 2003 to February 2004 in the morning. Fish samples were caught with gill nets set at the surface and bottom habitats. There were 11 fish families and 21 species. Osteoglossidae, Anabantidae, Channidae, Schilbedae and Cyprinidae were rare and occurred seasonally in fishermen catches, while Mormyridae, Cichlidae, Mochokidae, Characidae, Bagridae and Clariidae showed less variation and were more common. Characidae and Cichlidae were the most abundant (23.0 and 18.6% respectively) while Osteoglossidae, Channidae and Anabantidae were the least (1.7, 2.1 and 2.3% respectively). Clariidae and Mormyridae had the highest weight with 16.0% and 12.3% respectively, while Anabantidae had the lowest (3.4%). Surface water temperatures were generally higher than air temperatures during the afternoon, except from January to March when air temperatures were high (28.1 to 28.7 ºC) due to low relative humidity (39 to 70%). in the morning, surface water temperatures (25.5 to 26.3 ºC) became higher than air temperatures (25.2 to 26.0 ºC) from May to December, when relative humidity values were also high (50 to 88%). The differences between surface and bottom water temperatures was generally higher (0.7 to 3.1 ºC; P < 0.05) in the afternoon (0.2 to 0.8 ºC) due to sunlight. Temperature differences in the surface and bottom waters were usually higher during the dry season (P < 0.05), for similar reasons. Captures were higher in the dry season when the fish concentrated in the warmer, steadier and scarcer water. Minimal and maximal temperatures were different for surface and bottom waters (P < 0.05). However, there were no marked variations in temperature patterns or species distribution. Rev. Biol. Trop. 57 (1-2): 167-175. Epub 2009 June 30.

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Indiscriminate dumping of wastes into rivers without control measures is widely practiced in the developing nations of the World as it is observed in River Benue at Makurdi. To ascertain the health status and integrity of River Benue at Makurdi, water samples and sediments were collected monthly from five different locations on the shoreline of the river for a period of two years (July 2011-June 2013). The physico-chemical quality of the water samples were examined using standard methods. The sediments were examined for the presence and absence of macro benthic fauna. The mean values were generally within the WHO and the Nigerian Standard for Drinking Water Quality accepted maximum limit except for colour and turbidity. The result of ANOVA for all the parameters was significant during the seasons (P˂0.05), except for total dissolved solids (TDS), total suspended solids (TSS) and temperature (P˃0.05). Across the locations temperature, bicarbonate, nitrate, sulphate, phosphate and copper were not significant (ANOVA, P˃0.05). The result of the sediments showed that a total of 4,451 macro benthic fauna individuals comprising of 4 phyla and 21 taxa were obtained. Among this benthic fauna group, Athropoda had the highest population of 90.15%, Annelid 4.74%, Mollusca 3.39% and Platyhelminthes 1.7%. A significant relationship at some instances was noticed between benthic fauna group and some environmental variables indicating relationship between benthos and hydrochemistry of River Benue. It is recommended that the discharge of effluents and other waste into the River Benue should be controlled and enforced.

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