Assessing the Hazard of Picloram to Cutthroat Trout

Abstract

Water concentrations of picloram, comparable with those reported from field investigations, were used to simulate field exposures of cutthroat trout (Salmo clarki) to the herbicide. Picloram increased fry mortality in concentrations greater than 1,300 micrograms/liter and reduced fry growth in concentrations above 610 micrograms/liter. The chemical had no adverse effect on fry in concentrations below 290 μg/l. However, if persistent rainfall were to occur, resulting in continuous loss of picloram in runnoff, the maximum allowable concentration might be much lower than 290 micrograms/liter.