it seems if we force Malbatross born with fishing, then rollback the world in game, the Malbatross would never born again by fishing.
I've just test it, after rollback in game, I only get 70 fishes but never see Malbatross again.
1. force Malbatross appear around u by fishing.
2. rollback the world in game.
3. go fishing again and again and again, but no Malbatross come.