Andrew Scott, Virginia Tech

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Climate change and eutrophication has resulted in water temperatures and dissolved oxygen levels deviating from their natural levels. In the marine environment, a stressor can be described as a variable that, as a result of human activity, exceeds its natural level in variation. Predicting fish population responses to exposure to multiple stressors is a challenge because the extensive needed is rarely available.  We use an agent-based modeling to explore changes in population level variables of Atlantic Croaker (Micropogonias undulatus) as a response to single and multiple stressors. We performed a 2x2 factorial simulation experiment using temperature at 2 levels (cool and warm) and dissolved oxygen at 2 levels (normoxia and hypoxia). Using the four simulations, we analyzed the responses of two population level variables: spawning stock biomass (SSB) and average weight of age 5 individuals. Our results showed that the effect of warming and hypoxia on SSB was not well estimated with the additive model but was well estimated with the multiplicative model. In contrast to SSB, the average weight of age 5 individuals was well predicted by both the additive and multiplicative models. Our analysis using an agent-based model of croaker showed that in some cases one can accurately predict the population responses to warming and hypoxia from single stressor effects. The generality of these results needs to be determined.