R.D. Calfee G. Linder E. E. Little 2012 White sturgeon (<i>Acipenser transmontanus</i>) populations throughout western North America are in decline, likely as a result of overharvest, operation of dams, and agricultural and mineral extraction activities in their watersheds. Recruitment failure may reflect the loss of early-life stage fish in spawning areas of the upper Columbia River, which are contaminated with metals from effluents associated with mineral-extraction activities. Early-life stage white sturgeon (<i>A. transmontanus</i>) from the Columbia River and Kootenai River populations were exposed to copper during 96-h flow-through toxicity tests to determine their sensitivity to the metal. Similar tests were conducted with rainbow trout (RBT [<i>Oncorhynchus mykiss</i>]) to assess the comparative sensitivity of this species as a surrogate for white sturgeon. Exposures were conducted with a water quality pH 8.1-8.3, hardness 81-119 mg/L as CaCO₂, and dissolved organic carbon 0.2-0.4 mg/L. At approximately 30 days posthatch (dph), sturgeon were highly sensitive to copper with median lethal concentration (LC₅₀) values ranging from 4.1 to 6.8 &mu;g/L compared with 36.5 &mu;g/L for 30 dph RBT. White sturgeon at 123-167 dph were less sensitive to copper with LC₅₀ values ranging from 103.7 to 268.9 &mu;g/L. RBT trout, however, remained more sensitive to copper at 160 dph with an LC₅₀ value of 30.9 &mu;g/L. The results indicate that high sensitivity to copper in early-life stage white sturgeon may be a factor in recruitment failure occurring in the upper Columbia and Kootenai rivers. When site-specific water-quality criteria were estimated using the biotic ligand model (BLM), derived values were not protective of early-life stage fish, nor were estimates derived by water-hardness adjustment. application/pdf 10.1007/s00244-012-9782-3 en Springer Toxicity of copper to early-life stage Kootenai River white sturgeon, Columbia River white sturgeon, and rainbow trout article