Good questions! - which prompted my search for answers...

Rotenone Toxicity Study
"Fatal concentrations for the invertebrates studied are a factor of 10 to 100 higher than the piscicidal concentration used. Certain mayflies may be more sensitive.
As for amphibians, lethal concentrations of rotenone are species dependent, but in general amphibians are less sensitive than fish or invertebrates."

BTW, rotenone is one of the oldest known "insecticides" (alongside nicotine & nicotine sulfate).

Kelly Duffie
Cypress, TX