The study was conducted to determine the monthly variation in some physico-chemical parameters, fish species composition and diversity, and condition factor of the resident fish species in Dadin-Kowa reservoir. The water electrical conductivity and total dissolved solids, and pH were measured by Hanna conductivity meter model EC 215 and pH meter model H198107. Other parameters which include: water temperature, waterdepth, transparency, dissolved oxygen (DO), biochemical oxygen demand (BOD), carbon dioxide and water hardness were measured using standard methods. The fish samples were identified using standard descriptions keys. The Shannon Weiner diversity index was used to determine the diversity of fish species in the reservoir. One-Way Analysis of Variance (ANOVA) was used to test for significant differences in species diversity among stations and Duncan’s Multiple Range Test (DMRT) was used to separate the means where significant differences exist. Student’s T – test was used to compare the variation in physico-chemical parameters and fish diversity in dry and wet seasons. There was high significant (P ≤ 0.05) variation in the physico-chemical parameters with months in the reservoir except for water depth, carbon dioxide and hardness. There was high positive association between BOD and DO (r =1.00) and between carbon dioxide with EC and TDS (r = 0.80). Temperatures showed moderate significant positive relationship with carbon dioxide, BOD and DO. A positive and significant association was observed between TDS and EC. Water depth was found to significant negative association with temperature, EC, BOD, TDS, DO and carbon dioxide. Of the total 690 fish sampled, thirty (30) fish species representing eleven (11) families were identified. The family Mormyridae had the highest number of species (6) followed by the family Mochokidae (5) then the families Alestidae, Cyprinidae,Clariidae and Claroteidae while the families Malapteruridae, Polypteridae and Schilbeidae had the least number of species each. The highest percentage was in the family Mormyridae with 20.0% fish followed by Mochokidae with 16.7%. The family Malapteruridae, Polypteridae and Schilbeidae with 3.3% had the least catch. Of the total of 690 fish sampled, the highest percentage of 18.99% fish belongs to the genus Petrocephalus, followed by Heterobranchus with 16.23%. The least catch was in the genus Malapterurus with 0.72% fish. Out of total fish species sampled Mormyropsanguilloides, Clariasanguillaris and Schilbemystus had 14.5%, 8.7% and 8.6%respectively of the fish composition. Labeosenegalensis and Synodontisbudgetti had 6.9% and 5.8% respectively. While the remaining fish species had percentage occurrence of less than 5%. There was significant variation (P ? 0.05) in the number of fish species sampled monthly in the reservoir. The highest diversity index of 2.056 was in the family Cyprinidae. The least index value of 1.32 was obtained in the family Claroteidae. The degree of evenness of the families was lowest (0.8296) in Alestidae and highest (0.976) in Cyprinidae. The family Malapteruridae with the least individuals had the least dominance while the family Cichlidae had the highest value of 0.188. The genera Hyperopisus, Mormyropsand Malapterurus had the lowest indices while Petrocephalus, Clarias, Barbusand Oreochromishad the highest number of fish species. Highest condition factors of 1.1 and 1.09 were observed in Brycinusmacrolepidotusand Malapterurusminjiriya respectively. Lower values of 0.31 and0.30 were obtained in Chrysischthysnigrodigitatus and Momyropsanguilloides respectively. This indicates that the fish species in this study showed good physiological state and health condition. The study revealed marked monthly variation in the physicochemical factors, rich fish composition with important economic species and variation in condition factor of highly diversified fish community structure in the reservoir. It is hereby recommended that regular monitoring of the physicochemical parameters of water and sustainable management of the fisheries resources of the reservoir be encouraged.

CHAPTER ONE: INTRODUCTION

1.1    Background of the Study
The rapid urbanization of many towns and cities across the world necessitate the construction of reservoirs to supply these towns with potable pipe borne water. Dadin-Kowa reservoir is one of such water bodies located in the north east of Nigeria in Gombe State. It supplies municipal water to Dadin-Kowa, Yamaltu Deba Local Government Area and other parts of Gombe State. Reservoirs apart from their primary function also have secondary uses for fisheries and irrigation of farmlands (Ahmed and Philip, 2012).
Water is an essential component for life on earth. It contains minerals which are extremely important in human nutrition (Versari et al., 2002). However, the drastic increase in population results in an enormous depletion (Ho et al.,2003). It is observed that human activities are a major factor determining the quantity and quality of the water through atmospheric pollution, effluent discharges and use of agricultural chemicals, eroded soils and land use (Sillanpa et al., 2004). As pointed out by Kofi(2001), freshwater is indispensable and is sensitive as human activities have great impact on the quantity and quality of freshwater: both the quality and quantity of our planet's freshwater are under threat.
According to Roy and Mazumdar (2005), the use of water in the world has increased by more than 35 times over the past three centuries and recent estimate shows that 3240km3 of freshwater is withdrawn globally on annual basis. A major portion of this (69%) is used for agriculture, 23% for industry and the remaining 8% for domestic use. Owing to inadequate management of wastes, freshwater potential has been reduced due to widespread pollution. Studies have shown deterioration of water quality and low faunal abundance and diversity caused by stress imposed by effluents from land-based sources (Chukwu and Nwankwo, 2005). If left unchecked, these ecosystems will cause a serious threat to aquatic life as well as to man due to continuous depletion and eventual extinction of some fish species. Biodiversity is the variability among living organisms from all sources including terrestrial, marine and other aquatic ecosystem and ecological complex of which they are part (Ali, 1999). The diversity of fish mainly depends upon the biotic factors and types of ecosystem (Nanda and Tiwari, 2001). Climatic characteristics influence the water quality and quantity and that invariably affects biodiversity.
The general desire to protect freshwater fisheries has led to an expansion of research into their quality requirements in their habitat in terms of physico-chemical parameters such as pH, temperature, dissolved oxygen, transparency, salinity and electrical conductivity etc. These factors serve as base for the richness or otherwise of biological production of any aquatic environment (Imevbore, 1990).Several of these physico-chemical parameters have been studied on large man-madelakes in Nigeria by Adeniji and Ita (1977) and Adeniji (1981). Other works on physico-chemical parameters include that of Balarabe (1989) on Makwayelake, Oniyeet al. (2002) on A.B.U. reservoir, Ugwumba and Ugwumba (1993) on Awbalake in Ibadan. Kolo and Oladimeji (2004) studied the water quality and some nutrients level of Shiroro lake, Niger State.
Reservoirs have helped to harness water for drinking, irrigation, and industrial uses and have also brought about lacustrine conditions which are conducive in the maintenance of the fish stock that can be exploited through capture fisheries and aquaculture. It is necessary to maintain reservoirs by addressing the consequences of present and future threats of contamination and degradation of our water bodies. Azionu (2004)showed that the soil structure and composition, natural environmental hazards, biochemical oxygen demand, dissolved oxygen, pH, temperature, transparency , e.t.c. allinfluence the quality of the medium which in turns determine the health of the fish and their performance. Dadin-Kowa reservoir was created through impoundment of River Gongola in 1984 by the Federal Government of Nigeria with the goal of providing irrigation and electricity for the planned Gongola Sugar Plantation Project.

1.2    Statement of Research Problem
The distribution of fish species is affected by biotic and abiotic factors (Kadye et al.,2008). Akbulut (2009) reported some physicochemical parameters to significantly restrict survival, growth and distribution of fish. The Nigerian inland water bodies are primarily utilized for fishing by fisher folks (Adaka et al., 2014). Fisheries resources are on the decline in Nigeria due to over exploitation and inadequate management of her coastal waters (Lawson and Olusanya, 2010). Human activities, population growth, oil exploitation and exploration have been identified to alter the ecology of inland waters in Nigeria (Keremah et al., 2012).
Dadin-Kowa reservoir is a multiple used water body intended for hydro-electricitygeneration, irrigation and domestic use to serve Gombe, Bauchi and southern parts of Borno State. Multiple - use of water bodies can result in pollution with drastic effect on aquatic lives. Paucity of information on the present physical and chemical properties of Dadin-Kowa reservoir has necessitated this research.

1.3    Justification of the Study
The study of the physico-chemical parameters of an aquatic ecosystem is basic for understanding its biological productivity. Although each factor plays its individual role but it is the synergistic effect of various parameters which determines the composition and productivity of the flora and fauna. Conducive range of these factors is essential for obtaining optimum fish production (Bisht et al., 2013). For sustainability of fisheries resources in Nigeria, an adequate knowledge of species composition, diversity and relative abundance of fish resources must be understood and vigorously pursued (Lawson and Olusanya, 2010).
Information on the physico-chemical parameters and current fish species diversityof the reservoir is necessary for proper documentation and vital for sustainable management of the reservoir. Also, this study will provide information on the degree of pollution through determination of the physico-chemical factors of the reservoir, serving as pointers to the magnitude of deleterious anthropogenic activities.

1.4    Aim and Objectives
The aim of the study was to evaluate the variation in the physico-chemical parameters and fish species diversity of Dadin-Kowa reservoir.
The specific objectives were:

1. To determinethe physico-chemical parameters of Dadin-Kowa reservoir.
2. To determine the fish species composition and diversity in the reservoir.
3. To determine the length-weight relationship and the condition factor of some selected species of the resident fish species in the reservoir.

1.5    Research Hypotheses

1. The physico-chemical parameters of Dadin-Kowareservoir are within acceptable limits.
2. Dadin-Kowa reservoir is not rich in fish species composition.
3. There is no significant difference in the length-weight relationship and the condition of factor of fish species in the reservoir.