Population models can provide useful tools to assess potential exposure to, and effects from, pesticides – as well as evaluate mitigation options – on listed species by bridging the gap between laboratory endpoints derived from surrogate species and populations in the context of their habitat. We applied a hybrid model of the Topeka shiner (Notropis topeka), a small endangered cyprinid fish endemic to the US Midwest, to assess potential population-level effects of realistic exposures to a common fungicide (benzovindiflupyr). Topeka shiner populations were simulated in the context of the food web found in oxbow habitats that are the focus of ongoing habitat restoration efforts for the species. We applied realistic, time-variable exposure scenarios and represented lethal and sublethal effects to individual Topeka shiners using toxicokinetic–toxicodynamic models. We characterized the population-level effects of different exposure scenarios with exposure multiplication factors (EMFs) applied. In addition, we estimated the effectiveness of a vegetative filter strip (VFS) as a mitigation option. With fish in general showing the highest sensitivity to the compound, direct effects on simulated Topeka shiner populations governed the population-level effects while indirect effects mediated by the food web did not play a major role in simulated effects. The introduction of a vegetative filter strip of 15 ft between the treated area and the oxbow habitat was shown to be effective as mitigation because EMFs were 2 to 3 times higher than for the exposure scenario without VFS.

Amelie Schmolke (Waterborne Environmental, Inc.), Steven M. Bartell (Cardno, Inc.), Colleen Roy (Waterborne Environmental, Inc.), Dean Desmarteau (Waterborne Environmental, Inc.), Angela Moore (Syngenta Crop Protection, LLC), Megan J. Cox (Waterborne Environmental, Inc.), Nikki L. Maples-Reynolds (Waterborne Environmental, Inc.), Nika Galic (Syngenta Crop Protection, LLC), Richard Brain (Waterborne Environmental, Inc). Modeling realistic habitat and pesticide exposures to evaluate potential effects and mitigation for populations of an endangered fish species.