Sub-lethal effects of clothianidin on early life stage sockeye salmon (Oncorhynchus nerka)

One of the contaminants possibly contributing to declining sockeye salmon (Oncorhynchus nerka) in the Fraser River is pesticides. In this 4-month study, the effects of environmentally relevant concentrations of waterborne clothianidin (0.15, 1.5, 15 and 150 μg/L) on embryonic, alevin and early swim-up fry sockeye salmon derived from four unique genetic crosses of the Pitt River, BC stock were investigated. There were no significant effects of clothianidin on survival, hatching, growth or deformities, although genetic variation significantly affected these endpoints. Clothianidin caused a significant 4.7-fold increase in whole body 17β-estradiol levels in swim-up fry after exposure to 0.15 µg/L, but no effects were observed on testosterone levels. These results indicate additional examination of clothianidin and its effects on salmonid gonad development and the reproductive endocrine axis in general, is warranted.