Introduction

Pollution of the aquatic environment is a source of mounting concern not only in areas adjacent to industrial centres but in the oceans as a whole which are increasingly acting as a sink for the products of industrialized societies. Of particular concern are a group of structurally related compounds, the halogenated poly aromatic hydrocarbons (HPAHs) which include chlorinated biphenyls, dibenzo-p-dioxins and dibenzofurans (Fig. 1). These compounds readily become adsorbed to sediments and are only slowly metabolized in biological systems. Their lipophilic and persistent natures result in their bioaccumulation in organisms and magnification of their concentrations during passage up the food chain. These processes have been studied extensively in the Great Lakes of North America and in the Baltic, and there is strong evidence that they result in reproductive failure in fish-eating birds (Walker, 1990). In addition, HPAHs have been found in a variety of marine mammals, and much has been talked of the possibility that these compounds have contributed to reproductive failure and immune suppression in these animals, although direct evidence to support these contentions is scanty. Another group of common organic pollutants are the polyaromatic hydrocarbons (PAHs) (Fig. 1), which may be derived from the exploitation of petroleum or from the deposition of combustion products to rivers and oceans. These compounds are less persistent than HPAHs but are known to give rise to highly mutagenic and hence carcinogenic entities.

As with higher animals, there is very little evidence to connect pollutant body burdens of any of these chemicals directly with either reproductive failure or cancerous conditions in wild fish populations (Mix, 1986).