CHAPTER ONE

INTRODUCTION

In urban aquatic environments, fish may be exposed to myriad of substances at the same time produced by different kinds of anthropogenic activities. Biological changes in fish that are related to the exposure or to the effect of contaminants are called biomarkers and their use has led to good results on environmental risk assessment (Vander Oost et al., 2003).

Water is an important determinant of the socio-economic development (El-Nagger et al., 2016). It is the supreme fluids that promotes the human health and maintain the integrity of natural ecosystem. Water stimulates the biochemical processes of living organism and reduces the toxic effects of a broad spectrum of pollutant (Majumder and Dulta, 2014; Singh, 2014, El-Naggar, 2016). To function properly, water needs to be of adequate quality and free from harmful substances.

Addition of unwanted substances into the water bodies cause changes in the physical, chemical and biological characteristics of the aquatic system which lead to ecological imbalance.Industrialeffluents contribute a lot to water pollution forming a threat to aquatic plants and animals (Ramona et al., 2001). A greater part of the pollutants exhibit biomagnification and bioaccumulation capabilities with a broad spectrum of impacts, and stresses on aquatic organisms (Censi et al., 2006).

The pollution leads to a steady decline in the aquatic flora and fauna, particularly fishes. Wedemeyer (1996) reported that the fishes are more susceptible to stress than many other animals because of their intimate dependence upon their surrounding environment.

Industries are major sources of pollution in all environments. Based on the type of industry, various kinds of pollutants can be discharged directly or indirectly into the environment (Tilt, 2013). Waste water from industry may include sanitary waste of employees, processing waste from manufacturing plants, water emanating from washing the factory floor as well as those utilized in various cooling systems (Awaleh and Soubaneh, 2014). This may vary widely depending on the size of the industry and what is being produced.

The use of physiological and biochemical parameters as indicators of water quality has recently been developed to detect sub-lethal impacts of pollutants.  Prominent among these biomarkers according to Lohneret al., (2001) and Cazenaveet al., (2005), are haematological data and physiological variables, such as plasma levels of metabolites as documented by Digiulioet al., (1995) and ions (Engelhardt et al., 1996; Martinez and souza, 2002), levels of hormones like cortisol (Hontela et al.,, 1996; Barton et al., 1998; Hontela, 1998; Benguira and Hontela, 2000) and biochemical variables such as detoxifying enzyme activities (Paris – palacioset al., 2000; Teleset al., 2003).

Increased indiscriminate disposal of pollutants or toxicants such as fertilizers, herbicides, pesticides, insecticides, among others into water bodies in recent times, calls for serious concern by regulatory authorities (Warren, 1977).  IPIECA (1991) documented that in most countries, pollutants are constantly allowed to drain into the aquatic environments with little or no treatment given to reduce toxicity. These could possibly contribute to additional stress on the environment and the aquatic biota (Das, 2003; Fakayode, 2005).

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