Normal, natural, cyclical events occur in nature and will likely explain some of these reports. New viruses exposed to new populations. Lakes turning over. Winter die off. There is a yearly event in the White river in Arkansas where tons of minnows die and the trout go crazy. I was hoping to see this for my self this year.
How many times have you read on here where someone just recommends a little this toxin or a little that toxin to rid yourself of some unwanted creatures that may not only target the intended varmit(s)?
Nature has its own checks and balances, some more obvious at first glance than others. And even when an obvious answer may be present, you get more viewers when you sensationalize the story.