The use of the structural model for the assessment of enviornmental impact on coastal fisheries. Principles and procedures.

Abstract

The utility of the structural model as a tool for the assessment of environmental impact on coastal fisheries is described, together with its principles and procedures. This method uses existing information for structuring comprehensive ecological systems of fishing grounds and evaluating their functional change both directly and indirectly due to various impacts. A simple empirical formulation scheme is proposed as a means of quantifying the environmental impact. A set of variables, each of which indicates the rate deviation from the present state of each environmental factor, is used for the formulation. Each variable is normalized over the range (0-1) where we define the upper boundary for the present state and the lower boundary for the largest impacted state. Thus it also becomes possible to use simple multiplication to calculate the effects of multiple factors on a single factor. By inputting an initial value to the formulated structural model, one can estimate possible impacts on fisheries, for example, in terms of relative catch loss. Although this method has several limitations when handling feedback processes, etc., it seems to make conventional methods more concrete and quantitative.