What do we mean by the term water quality? Which aspects of water quality are important to salmonid fish? How do these factors operate through the life-cycle of salmon or trout?
Water Quality for Salmon and Trout attempts to explain the answers to these questions in terms that are satisfactory to both the layman and the non-specialist scientist. The first step is to give a brief description of certain physical and chemical attributes of clean water. This description may be found in Section 2 and is mostly concerned with fresh water but concludes with a note on estuarine waters. Where it is felt that a more detailed account of some feature may interest readers, this detail is given as a footnote; this technique is employed in later Sections too. Section 3 then considers the water-quality requirements of salmonids in general and at specific points in their life-cycle. With this introduction to the characteristics of clean water and the needs of fish, the reader can proceed to Sections 4 and 5, which essentially describe how things go wrong. (Section 4 is "Causes of deterioration in water quality" and Section 5 is "The effects of pollutants on fish".) At worst these effects are a "fish kill" but there are many other more subtle biological signals that all is not well in a body of water, and Section 6 describes some of these "biotic indices". Finally, we should not leave the subject of water quality without giving an account of the administrative provisions in force nationally and throughout the European Union, and the various useful guidelines, not part of legislation, that have been prepared to assist in defining standards to safeguard fresh water life.