Which big cats eat fish? The big cats are the tiger, lion, jaguar and leopard. They will all eat fish when necessary but they won’t be a preferred prey item, far from it. This is because they’re too small and other prey items are easier to hunt.
Tigers will kill any animal that puts itself in a vulnerable position and few animals appear to be immune to tiger predation. Tigers will eat almost anything they can catch from frogs to elephant calves. Tigers are excellent swimmers. They spend a lot of time in the water.
I cannot find a direct reference to wild tigers eating fish in the best books on the wild cats but I will make a presumption that they do eat fish when the occasion presents itself which would be rarely. In captivity they will eat fish – see photo:
As for lions, I do have a direct reference to eating fish as follows:
“Ungulates are their principal prey, but birds, hares, ostrich eggs, python, fish, crocodiles and even other Lions are on the list of recorded prey”. – Wild Cats Of The World
Concerning jaguars, this fantastic wild cat species also likes water. They are opportunistic predators able to kill and consume almost any type of prey they encounter. Prey items range from turtle eggs to domestic cattle. Jaguars do eat turtles by crushing the carapace using their massive bite force. When captive they can be seen eating fish as demonstrated in the photograph below. Although fish will certainly not be a primary prey item, far from it. Their preferred prey is probably the whitetail deer or the peccary. There are some fantastic pictures of jaguars swimming underwater on the internet. They are completely at home in water.
The common leopard is a very adaptable big cat whose habitat covers a vast area of the planet. Once again they are opportunistic predators killing vulnerable animals as they are encountered. I can’t find a direct reference to this cat eating fish but amphibians and reptiles are prey items. I would suspect that if somehow, somewhere a dead fish presented itself it will be eaten by the Leopard. I would doubt that they deliberately prey upon fish but they doubt good swimmers but less so than the tiger and jaguar.