THE USE OF FISH IN ECOLOGICAL ASSESSMENTS

Fish provide powerful tools for assessing aquatic environments. Three attributes are especially significant: the sensitivity of fish to most forms of human disturbance, their usefulness at all levels of biologi cal organization and the favourable benefit-to-cost ratio of fish asse ssment programmes. Fish can be used as indicators over wide temporal a nd spatial ranges. Because they cover all trophic levels of consumer e cology, fish can effectively integrate the whole range of ecological p rocesses in waterways. Fish have been used in many different roles for assessing river health and monitoring responses to remedial managemen t. Three of these applications appear to have particular value for man agement of Australian rivers: (i) automated systems monitoring fish ve ntilation can provide sensitive, broad-spectrum and continuous sensing of water quality to protect receiving waters or water-supply intakes; (ii) programmes collecting routine data on commercial or recreational fisheries can be designed and analysed so as to isolate confounding e ffects due to fishery-specific factors and, hence, used to detect and monitor environmental change on large scales; (iii) the Index of Bioti c Integrity (IBT) can be modified to suit Australian conditions and fi sh communities to meet the important need for a predictive model of aq uatic environmental quality. The IBI is a quantitative biological tool with a strong ecological foundation that integrates attributes from s everal levels of ecosystem organization. Examples of the use of IBI el sewhere suggest its robustness, flexibility and sensitivity can cope e ffectively with the low diversity of the Australian fish fauna and the dominance of ecological generalists. A provisional structure is sugge sted for a test of the IBI in four riverine regions of New South Wales .