Copper Concentrations in the Upper Columbia River as a Limiting Factor in White Sturgeon Recruitment and Recovery

Abstract Currently there is little natural recruitment of white sturgeon (Acipenser transmontanus) in the Upper Columbia River located in British Columbia, Canada and Washington, USA. This review of life history, physiology, and behavior of white sturgeon, along with data from recent toxicological studies, suggest that trace metals, especially Cu, affect survival and behavior of early life stage fish. Sturgeon free embryos, first feeding embryos, and mixed feeding embryos utilize interstitial spaces between gravel. Although concentrations of Cu in the water column of the Upper Columbia River are typically less than US water quality criteria defined to protect aquatic life, samples at the sediment–water interface were as large as 24 µg/L and exceed the criteria. Toxicological studies reviewed here demonstrate mortality, loss of equilibrium, and immobility at Cu concentrations of 1.5 to <16 µg/L and reduced swimming activity was documented at 0.88 to 7 μg/L. Contaminated invertebrates and slag particles provide other routes of exposure. These additional routes of exposure can cause indirect effects from starvation due to potential lack of prey items and ingestion of contaminated prey or slag particles. The lack of food in stomachs during these critical early life stages may coincide with a threshold “point of no return” at which sturgeon will be unable to survive even if food becomes available following that early time frame. These findings become especially important as work progresses to enhance white sturgeon recruitment in the Upper Columbia River. To date, decisions against including trace metals as a factor in sturgeon recovery have focused on surface-water concentrations and measurements of lethality (LC50) to establish threshold concentrations for sturgeon sensitivity. However, information provided here suggests that measurements from the sediment–water interface and effect concentrations (EC50) be considered with white sturgeon life history characteristics. These data support minimizing Cu exposure risk to enhance a successful white sturgeon recovery effort. Integr Environ Assess Manag 2020;16:378–391. Published 2020. This article is a US Government work and is in the public domain inthe USA. KEY POINTS Review of current toxicological data provides a link between the hazard of Cu exposure and limited recruitment of white sturgeon in the Upper Columbia River (UCR), located in British Columbia, Canada and Washington, USA. Copper sensitivity of early life stages interpreted with life history, physiology, and behavior provide insight into the likely exposure routes of white sturgeon. Recent data on Cu concentrations in the sediment–water interface and shallow porewater along with effect concentrations including effective mortality and behavioral changes provide support for considering Cu exposure as part of the white sturgeon restoration plan. Contaminants in the UCR likely contribute to recruitment failure of white sturgeon in the UCR, and these data support minimizing Cu exposure risk to enhance a successful white sturgeon recovery effort.

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