Description of Work The sensitivity of listed species of fish or amphibians was evaluated in acute and chronic toxicity tests conducted with a range of inorganic or organic chemicals with different toxic modes of action. Results of these studies indicate that the acute or chronic sensitivity of rainbow trout, but not fathead minnow, frequently provided protective acute or chronic toxicity thresholds for most of the listed species evaluated. However, only a limited number of species of sculpins or darters were included in this evaluation, and not all species tested occurred in the Great Lakes watershed. The objective of the proposed study will be to: (1) provide additional chronic toxicity data for sculpins or darters indigenous to [...]