INFLUENCE OF ECOLOGICAL FACTORS ON THE RELATIONSHIP BETWEEN MFO INDUCTION AND FISH GROWTH - BRIDGING THE GAP USING NEURAL NETWORKS

Relationships between molecular and biochemical effects of contaminant exposure and organism-level effects are difficult to establish primar ily because. (1) the large differences in time-scales of the responses ; (2) the complexity of mechanisms involved in such relationships; and (3) the influence of ecological factors on the expression of higher-l evel responses to stress. In this study we investigated the relationsh ip between mixed function oxidase (MFO) induction and growth in fish a s influenced by principal ecological factors in the environment, such as habitat quality, competition and food availability. Because of the complexity and non-linearity of interactions among these factors, we a pplied a back-propagation neural network approach to investigate this relationship. Inputs into the network included an indicator of contami nant exposure (7-ethoxyresorufin O-deethylase, EROD) and several ecolo gical variables, while growth rate served as the single output variabl e. Under. the field conditions and contaminant exposure regimes observ ed in this study, EROD in the model simulation contributed minimal mar ginal ability to predict growth. Indirect effects of contaminants on g rowth could occur, however, through influences on food chain processes or behavioral dynamics of fish populations. Copyright (C) 1996 Elsevi er Science Ltd.