Model organisms are often used in ecotoxicological studies and environmental risk assessments; however, species differences in responses to toxicants exist. A meta-analysis identified normal biomarker ranges for rainbow trout (RT) and brook trout (BT), and showed that RT had greater whole-body lipids and plasma T4 levels than BT. Exposure to selenium inhibited cortisol secretion of trout adrenocortical cells; however, RT were more sensitive than BT. To investigate species vulnerability at the individual level, RT and BT were stocked into reference and selenium-contaminated pit lakes. Fish accumulated more Se from selenium-contaminated than reference lakes, and selenium accumulation was similar between species. Chronic selenium exposure had a greater energetic cost for RT than BT, but this was mitigated by food availability. Chronic selenium exposure decreased plasma T3 and T4 levels, but did not alter other endocrine or oxidative stress biomarkers. This project highlights the need for both species- and site-specific risk assessments. / xiv, 171 leaves : ill., maps ; 29 cm

Selenium (Se) is an essential element, toxic at concentrations only slightly above those required. It can become detrimental to fish health when available in excess in the aquatic environment. This study examined the effects of Se on adult female rainbow trout, brook trout, and cutthroat trout fed Se-methionine for five months, and on their larvae. Differences between fish species and between tissues were observed in the accumulation of Se in adults, and dose-dependent effects of Se on plasma thyroid hormone concentrations in brook trout, gonad size in all three species, and indicators of oxidative stress in rainbow trout and cutthroat trout, were detected. Survival of larvae and swim-up success decreased with increasing egg Se concentrations in rainbow trout and cutthroat trout, however, the same effects were not observed in brook trout. Data from this study provide new evidence for species-specific Se accumulation and toxicity in salmonid fish. / xi, 123 leaves : ill. ; 29 cm