Pesticides, aquatic food webs, and the conservation of Pacific salmon

Pesticides pose complex threats to the biological integrity of aquatic ecosystems. In the western US, pesticides have contaminated many surface waters that provide habitat for endangered salmon. These iconic species depend on the productivity of rivers, lakes, and estuaries to provide food for juvenile growth, a key determinant of subsequent marine survival. Despite extensive societal investments in salmon habitat restoration in recent years, the role of pesticides as a limiting factor for salmon recovery has received little attention. Pesticides can be toxic to primary producers and macroinvertebrates, thereby limiting salmon population recovery through adverse, bottom-up impacts on aquatic food webs. The integration of toxicology, environmental chemistry, population biology, community ecology, landscape ecology, conservation biology, and environmental policy is needed to better understand these indirect effects of pesticides on endangered species. We highlight key information gaps and discuss how future research on pesticides and food webs can most effectively guide the long-term conservation of imperiled fish species.