My ducks like to pursue baitfish till the fishes die. Probably they die from heartattack as no wound or injury is noticeable, even their scales remain intact. Then my runners pick and throw the dead fish out from the pond. I slice the fishes to duck bite chunks and feed them from hand. It may sound cruel, but these fish would otherwise be placed on hooks to catch pike with as livebait - better make them an entertainment and healthy high-protein food for the birds.
Also I raise mealworms for the birds (yes, they are expensive), and I already have a dozen of grown bugs, I hope they will lay eggs soon, which means more more more mealworms.