The current approach of assessing risks to fish from exposure to pesticides relies on effects data on individuals.  However, the effect of a single stressor on populations may depend on multiple factors including a species’ life history, which life-history traits are impacted by the stressor and to what degree, the duration and frequency of stress occurrence, and variability in population dynamics. Population models can combine effects of stressors observed on organisms with species-specific life histories and variability in population dynamics, and project population-level outcomes over extended time periods.  In this study, we used an existing matrix population model of the Slackwater darter (<i>Etheostoma boschungi</i>), a species listed as threatened under the U.S. Endangered Species Act, to assess stress levels that may cause population decline. We represented direct effects as changes in survival and fecundity, and indirect effects as decreased food availability. From the scientific literature, we used information on the relationships between reduced food availability, body size and survival and fecundity in fish, and incorporated these relationships in the Slackwater darter model. We analyzed exposure-effects relationships of a pesticide with the model to estimate exposure levels that could cause long-term impacts on population abundance and persistence. Further, we assessed the applicability of the modeling approach to a range of species by analyzing model predictions for potential pesticide impacts on survival and reproductive rates for related fish species with similar life histories. By combining information on life history and direct and indirect effects, population models can provide a valuable tool to assess potential risks of pesticides to populations of listed and other non-target species over ecologically relevant time periods.

Using population models to gain insights into direct and indirect effects of pesticides on listed fish populations

254th National Meeting (2017)

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