Yep, lee s has it right. We just can't leave well enough alone. Recent history certainly bears that out doesn't it. On a piscatorial note, another CA lake that was rotenoned is near the town of Mt. Shasta. The fin and fur authority decided the introduced lake trout had become trash fish, so of course they had to kill the lake.
They were very proud of themselves once the lake had been re-established as a decent rainbow and brook trout impoundment. I'm sure they know that not all of the lakers were killed with the rotenone and I certainly do.
One I got a look at was prolly a 48 incher and for some reason was cruising along at the same speed of my drifting jon-boat, in the shadow created by same. Anyway, good point lee s...and no, we humans sure can't leave anything just 'be'.