Ashleigh M. Pilkerton | Geology Reports

USGS2025

Suspended sediment and fisheries: An exploration of empirical relationships

Objective: Sediment has an important role in aquatic ecosystems, however, excess sediment can negatively impact fish and other aquatic life. Quantifying the response of aquatic life, particularly fish, to suspended sediment is important for natural resource managers tasked with developing sediment management guidelines to protect aquatic ecosystems. Our goal was to assess the ability of established, revised, and alternate severity of ill effect (SEV) dose-response models to predict the impact of suspended sediment on fish. Methods: We synthesized existing literature to develop an expansive dataset that relates suspended sediment concentration and exposure duration to biological effects on fishes and assessed the predictive ability of established and revised SEV dose-response models. We investigated potential sources of variation in biological responses to suspended sediment dose and explored two alternative approaches for assessing the effects of suspended sediment on fish: 90th quantile SEV dose-response regression models and logistic SEV dose-response models. Results: We found that both established and revised linear SEV dose-response models poorly quantify fish biological response to suspended sediment. Quantile SEV dose-response regressions also performed poorly. More promising are logistic dose-response models that identify sediment thresholds where major effects of sediment on fish can be expected to occur. We demonstrate that fish biological response to suspended sediment is modulated by sediment particle size, water temperature, and dissolved oxygen levels, suggesting additional environmental and biological variables to consider when evaluating the effects of suspended sediment on fish. Conclusion: We contribute revised and novel empirically derived tools for predicting the effects of suspended sediment on fish and demonstrate how environmental variables and life stage may modulate fish biological response. Our work illustrates challenges associated with predictive modeling and some potential sources of variation. While empirical models integrating biological stress response to suspended sediment may help natural resource managers capture potential impacts of this stressor, a cautious approach that considers co-acting stressors may be most effective for sediment management that is protective of fish.

North American Journal of Fisheries Management↗

USGS2025

Linking suspended sediment conditions to hyporheic dissolved oxygen and fine sediment deposition in salmonid spawning habitat below an irrigation dam, Park County, Wyoming

Dams are essential for water resources management but impose notable effects on fluvial sediment transport and downstream river morphology by reducing or altering the timing of sediment loads. We explored the relationship between dam sediment management and downstream sediment dynamics in the context of riverine fisheries management. We quantified the effects of dam sediment management operations on downstream salmonid spawning habitat during two fall water-level drawdown periods: an experimental drawdown leading to sediment release or a typical slower drawdown intended to minimize release of sediment. The experimental drawdown increased deposited fine sediment and decreased hyporheic dissolved oxygen levels. However, the typical drawdown did not increase fine sediment deposition or decrease hyporheic dissolved oxygen. We quantify the immediate impacts of dam operations using a number of water column and substrate metrics, and demonstrate the potential for sediment flushing operations to have short-term seasonally persistent effects on salmonid spawning habitat. Common surrogates of suspended sediment concentration (i.e. turbidity) were poor indicators of salmonid spawning habitat, especially when sand was the dominant grain size. Instead, measures of suspended sediment concentration such as acoustic backscatter sensors and depth-integrated samples, combined with discharge, appear to be better suited for monitoring and inferring the impacts of dam operations involving sediment releases on salmonid spawning habitat. We demonstrate the importance of understanding sediment particle sizes, monitoring relevant water column conditions in real-time, and provide options for effectively monitoring the downstream impact of dam operations. This work can help managers balance dam sediment management operations with ecological priorities.

Wyoming↗