The Effects of Chronic Exposure to Environmentally Relevant Levels of Waterborne Cadmium on Reproductive Capacity and Behaviour in Fathead Minnows

Cadmium (Cd) is a priority pollutant in aquatic ecosystems because of its highly toxic effects at low concentrations. Recent work has highlighted that at sublethal concentrations, Cd can impair the ability of fish to respond to important sensory cues. In the present study, we examined whether chronic exposure to environmentally relevant concentrations of waterborne Cd (1, 2.5 and 5 μg/L) can result in reproductive impairment in fathead minnows (Pimephales promelas) as measured by the standard Organization for Economic Cooperation and Development (OECD) 21-day reproductive assay. In addition, we also evaluated the effects of chronic waterborne Cd exposure on Cd accumulation in target tissues (liver and ovary) and plasma estradiol level in females and on the reproductive behaviour of fathead minnows. We found that the standard endpoints used in the OECD reproductive assays (e.g., egg production, number of spawning attempts, brood size) are more sensitive to Cd exposure than behavioural endpoints; however, the traditional method of interpreting reproductive impairment may underestimate toxic effects. Cadmium accumulation in liver and ovary of fish increased with increasing Cd exposure concentrations; however, plasma estradiol level remained unaffected. Reproductive capacity in fathead minnows decreased at waterborne Cd concentrations as low as 1 μg/L. The findings of our study have important implications for understanding the effects of chronic Cd exposure in metal-impacted feral fish populations.