1.2 Research Problem
Water is one of the major components of environmental resources that are under threat either from over exploitation or pollution exacerbated by human activities on the earth surface (Efe, 2002). Studies in Nigeria have shown that water resources are easily contaminated from anthropogenic activities in most cities (Kaizer et al., 2001, Obasi and Balogun 2001). It has been observed that agricultural wastes, manure, fertilizers and pesticides find their way into streams, rivers and lakes through run-off and therefore enrich the organic content of water bodies (Beadle, 1974 and Gopal et al., 1981) and leading to eutrophication (Mitchell, 1975). Eutrophication becomes nuisance in lakes because of impaired water quality which leads to prolific weeds growth, excessive algal blooms and deteriorating fisheries (Gelin, 1978). In Doma reservoir there are three fishing villages around the reservoir and water treatment plant. The villagers around this reservoir are involved in fishing and agricultural activities where herbicides and pesticides are being used. They also used the reservoir for other activities such as bathing and washing of their cloths, pots and plates. All these activities are likely to alter the quality of water in the reservoir which may in turn affect the life of aquatic organisms.
Jamu and Ayinla (2003) reported that the fish yields of most Nigeria inland waters are generally on the decline. The decline of these fisheries has been attributed to a wide range of causes ranging from inadequate management of fisheries resources to environmental degradation of water bodies. Fishing activities in Doma reservoir is so high and it has been observed that the fishermen are found of using different fishing gears including gill nets of smaller mesh sizes and fishing is all year round without opening and closing season, these