It would be interesting for some one to test the fish on the beach to see if they all died within a few hours of each other, I'm guessing they didnt. That's a lot of by catch for just one occassion, I'm guessing most of it was frozen and thawed prior to being dumped.
They are out there every day but you dont see tons of dead fish every day of the week, but just now with all the public interest on imported polluted catfish, all this top grade fish ends up dead on a very popular beach. Just a bit too coincidental for me.