CRITERIA FOR THE EVALUATION OF ALTERNATIVE ENVIRONMENTAL MONITORING VARIABLES - THEORY AND AN APPLICATION USING WINTER FLOUNDER (PLEURONECTES-AMERICANUS) AND DOVER SOLE (MICROSTOMUS-PACIFICUS)

The design of environmental monitoring programs is frequently hampered by a lack of objective, quantitative criteria for evaluating alternat ive monitoring variables. In this paper we describe two such criteria, which we call samples required - the number of samples required to de tect a given change in value - and information imparted - the amount o f environmental information revealed by the monitoring variable. We th en use these criteria to evaluate fin erosion in winter flounder (Pleu ronectes americanus) and Dover sole (Microstomus pacificus) as marine environmental monitoring variables. Two methods for determining the sa mples required use contaminated and reference areas to estimate the sa mple statistics of a hypothetical impacted population. The first metho d is based on the overall difference in the proportions of diseased fi sh in the reference and hypothetical populations. The second treats th e proportion of diseased fish in individual trawls as the variate and determines the samples required based on the mean and variance of the reference and contaminated populations. We use both methods to predict the number of trawls needed to detect an increase of 200% in fin eros ion in the reference population. The first method had greater statisti cal power but assumes spatially homogeneous populations. The second me thod accounts for environmental patchiness. For Dover sole it predicte d 1661 trawls would be needed to detect the 200% increase. An estuarin e winter flounder population would require 74 trawls, and an oceanic w inter flounder population would require 142.5 trawls. It appears that fin erosion in winter flounder may be a useful indicator of environmen tal contamination, but several stipulations apply. Migration may infla te the number of diseased fish observed in the reference population, a nd a more detailed etiology of the disease is required, including an u nderstanding of what contaminants are responsible for manifestation of the disease.