Rieber it may help if you studied the hydrodynamics of rivers a bit then perhaps you may understand how it could happen.
I think it was back in '96 or so where a considerable number of large sturgeon where found dead in the Fraser. It was speculated that in the heat and low water of the time some of deep holes (that can be 90+feet) may have become oxygen depleted and fish that went in these died. However no one cause of the studied sturgeon mortality was found.
Oh and wasn't angry at all. You do a Don Knotts routine. Me I am more like Gilbert Gottfried:
https://www.youtube.com/watch?v=XkLqAlIETkASuggest you give your old friend Pamela a call, tell you heard a big bloated dead sturgeon was found in a nearby lake and it made you think of her. She'll be thrilled to hear from you!
have a nice day now.