This is a long shot, but why not speculate, this is the internet-

Seems to me there is very little security at Blue Creek. The conspiracy theorist in me thinks it could be possible that an environmental extremest could simply open the gates early and let those fish out prior to them being mature, thus killing them.

It happened at Tokul Creek (but it helped them), why couldn't it happen here.

There are lots of people cheering the fact that a bunch of Hatchery fish are dead, I don't think its a stretch to think some fanatical person could have single handedly killed a bunch of hatchery fish.

My questions are....

300K fish die an nobody notice an extra amount of dead fish laying in the ponds? (seems fair even if there are some birds around)

What security measures are in place at this facility? Camers? Fences? Locks?

What kind of investigation was done?