Most of the oil that leaked out of the deep water horizon blown out oil well on the ocean floor is still sitting on the ocean floor. It doesn't just go away.

If this was a low oxygen thing then many other fish species would have died. With the currents in the ocean the oxygen levels don't normally get low enough to kill that many fish of one species. It's probably some sort of disease that's spread though out this one species. But I'd still bet that the root cause of this fish kill is coming from the oil that still out there on the bottom of the gulf of Mexico. Everyone knows that oil contains lots of toxic organic compounds. And they can get into the food chain starting with the smallest of creatures that can bio accumulate the toxic materials up higher in the food chain. With each additional larger animal going up the food chain the toxin are concentrated more and more.

I'd bet big money that the Florida Area Chamber of commerce people who's job it is to bring tourist and money to that area are not happy with the fish kill or the oil spill and it's continuing results and like the movie JAWS will try to deflect any mention of that oil spill which could turn off tourist. But I know that my neighbors had a bad experience at the Beach in Destin Florida. Who wants to go lay out or swim in waters filled with dead fish? Not me. Maybe that area needs more time to fully recover from the disaster of the oil spill. Things living in and on the ocean bottom are still being effected by that oil is my guess.