Acute hyperbilirubinaemia in rainbow trout (Salmo gairdneri) caused by resin acids.

1. The effects of resin acids on the development of, and recovery from jaundice in rainbow trout were studied. 2. At 0.4 mg/l or higher resin acid concentration, fish developed jaundice in 2-4 days at water temperatures over 17 degrees C and recovered from severe intoxication within 6 days. 3. Jaundice results at least partially from insufficient secretion of conjugated bilirubin into the bile, probably because resin acids and bilirubin share a common secretion pathway. 4. The activity of liver UDP-glucuronosyltransferase and concentration of plasma bilirubin are sensitive indicators of the exposure of trout to discharges containing resin acids.