Cats are a much less likely predator of fish. The link between cats and fish is strictly man made because other meats were considered too good to waste on catfood in previous times. Fish is not a natural food of cats nor is it even good for them.

rofl

They would sit for hours and watch them but I never saw any evidence that they actually scooped any from the pond. My own cats and the neighbors and stray cats are fascinated by the fish swimming, in the front ponds with no fence or fish there are treefrogs and tadpoles and they are all fascinated by them too but we have not found any froggie corpses. Nor seen them actually catch one. Again when the paw gets wet, they jump back and shake it.

We watch them for hours out the front window. Having the "nature" ponds out front is almost better than TV. We've seen opossums drinking too but raccoons are the only ones who do any damage.

They do present us with dead rats, mice and an occasional house sparrow though. I'd like to pay them a bounty on the dang starlings. IF they got a fish or a frog, I have no doubt that we would find the corpse in the house or on the back porch where they leave everyone else.....

The only fish I would truly worry about being killed by cats are fancy goldfish like fantails that don't swim well at all and have to stay near the surface. They wiggle so enticingly that they are impossible to resist and they can't dive like comets or koi do to escape. I can then imagine the cat playing with it until it died and then walking away thinking all the fun has gone.