For 20 years, the mystery behind what was killing coho salmon in Seattle’s urban creeks seemed unsolvable.
Every time it rained, fish would begin swimming in circles, floating belly up just a few hours later. Scientists looked at heavy metals, various chemical contaminants, water temperature and oxygen levels, but none of these things were the problem.
Great Lakes Now
https://www.greatlakesnow.org/2022/01/great-lakes-fish-populations-tires/