The occurrence of several legacy and current-use pesticides in water, sediments, and invertebrates poses substantial risks for juvenile Chinook Salmon rearing in the Sacramento-San Joaquin Delta. Although pesticides are known to be present in juvenile Chinook Salmon and their invertebrate prey in the Delta, the nature and severity of effects of pesticide mixtures on fish and the spatial and temporal variability in those effects are unknown. The overall goal of this project funded by the State Water Contractors of California is
- Objective 1. to apply a response spectrum model recently developed by our research team (We are currently finishing the models from the RSM project) to assess spatial and temporal differences in impacts of pesticide mixtures on salmon rearing in the Delta.
The response spectrum model enables prediction of the sub-lethal (behavioral and physiological) effects of pesticides in juvenile Chinook Salmon from measurements of pesticide concentrations in fish tissues. Spatial and temporal variability in pesticide concentrations in salmon and model-predicted effects of pesticide mixture residues measured in fish will be assessed using juvenile, fall-run Chinook Salmon collected from different locations in the Delta during annual monitoring surveys (including archived specimens from collections in prior years) and using caged, hatchery-origin salmon deployed in different locations in the Delta. The proposed research will enable a predictive assessment of the likelihood of Delta pesticide loadings to cause negative individual-level effects and population declines. Results will support the development of management and remediation strategies for pesticides in salmon rearing habitats. They will also provide a framework for evaluation of habitat restoration efforts through improved understanding of how risks and effects of bioaccumulated pesticides in juvenile Chinook Salmon vary across habitats in the Delta, including reconnected floodplain rearing habitats. Information on spatial variability in pesticide bioaccumulation in salmon may also provide insight into sources of these contaminants.