Effects of orally administered steroids on lake trout and Atlantic salmon

Lake trout (Salvelinus namaycush) and Atlantic salmon (Salmo salar) fed 30 mg β‐estradiol/kg of feed for 100 d from first feeding had liver and kidney pathology similar to but much less severe than that previously reported for rainbow trout (Oncorhynchus mykiss). Mortality was not affected. Both lake trout and Atlantic salmon treated with estradiol weighed significantly less than control fish at the end of the treatment period and at 200 d posttreatment. Testosterone‐treated fish of both species weighed less than control fish at the end of the treatment period. By day 200 posttreatment, testosterone‐treated and untreated lake trout weighed the same, but testosterone‐treated Atlantic salmon were heavier than control fish. Estradiol treatment produced an all‐female population of Atlantic salmon but not of lake trout. Testosterone at 5 mg/kg feed increased the ratio of males to females in both species.