When our two black jaguars were younger and used to go in their pool, we would occasionally put live fish in for them to catch as an enrichment. We would get the fish from Arizona Game & Fish from their breeding ponds that they stocked for release for fishermen. I'm not sure what they were (maybe trout or tilapia), but definitely smaller than pacu. The one time I saw it, one of the jaguars would dive underwater, catch one, take it up on the bank and eat it, then go in for the next one. Her sister did not like to go in the water any more (she used to) so just sat on the bank and watched. Now neither one of them goes in the water anymore, so we had to stop doing that, though we still occasionally do it for otter and polar bear.
The zoo are getting smaller fish so they can re-introduce the jaguar back into the exhibit, but need to get someone to take the bigger ones is the harder part