USING REPRODUCIBLE PERFORMANCE VARIATION AND GROWTH AS THE BIOMARKERS TO PREDICT TOLERANCE TO COPPER IN JUVENILE RANIBOW TROUT (ONCORHYNCHUS MYKISS)

Abstract

This study investigated whether or not growth and reproducible performance variation (i.e: biomarkers) in juvenile rainbow trout could be used to predict Cu sensitivity in individuals. Therefore there were two main objectives. The first was to identify and describe reproducible performance variability in individual fish. This was accomplished by evaluating individual performance in a series oftests designed to challenge the resting physiology ofthe fish (ie: challenge test). With the exception of growth, the performance measures had to show both individual variability and reproducibility from trial to trial. The second objective involved examining the relationship(s) that the biomarkers had on an individual’s tolerance to copper. This was accomplished through the use of both univariate and multivariate analytical techniques to determine how each biomarker affected tolerance individually, as well as how each ofthe biomarkers interacted with one another to affect tolerance. In addressing these objectives, this study has produced four important results. The first is that the reproducible performance variation identified in each ofthe challenge tests is real, and the tests can therefore be used as biomarkers ofsensitivity. Second, the performance of an individual in any one challenge test is unrelated to its performance in the others. Third, individual performance in the challenge tests did not significantly predict growth. Fourth, sensitivity to copper can be predicted, although a significant prediction is contingent upon two factors. The first is that multiple biomarkers be measured in each individual, and multivariate analyses be conducted to examine how the biomarkers interact with one another to effect tolerance. This is in contrast to examining how each biomarker effects tolerance individually. Second, the appropriate ‘suite’ of biomarkers must be evaluated. Not all combinations of biomarkers will convey tolerance, so it is important to ensure that all possible combinations ofbiomarkers are evaluated for their effects on tolerance. Based on the results ofthis study, the following conclusions are apparent: (1) individual variation amplified through the use of challenge tests is a useful tool for predicting individual tolerance; (2) tolerance cannot be reliably predicted using individual biomarkers; (3) multivariate analysis is a valuable tool for improving both interpretation and analysis of data with multiple biomarkers; and (4) since individual tolerance can be predicted, mortality due to copper exposure cannot be completely random.