For quite a while, Delta had an L-1011 flight that went Tampa-Atlanta-London Gatwick (and return) -- I wound up on the domestic leg at least a couple times, connecting to or from other Delta flights. While boarding in Tampa, you could see the cargo handlers loading box after box of tropical fish.
There is a McDonalds on Rockaway Blvd across from many of the cargo terminals (bldg 79)at JFK. One of my last jobs before retiring was working on a renovation of a large cargo building. So I drive over to pick up lunch, and there is a pickup truck from a cargo handler loaded with boxes of tropical fish. It was about 10 degrees out, all I could think of was the phrase "this isn't going to end well" Delta had a fair number of the -500 tristars that were a little shorter, but had upgraded engines, and quite a bit of extra range. Wouldn't be surprised if it was on that route.