Lazy trout

I don't know if this is a bug issue or not. I have had a pond with 10 trout in it for a couple of years now, and they're pretty boring. All they produce is fish eggs. Okay, once they gave me a basic-quality rainbow shell. But the rest of the time, it's just eggs. The whole reason I got them was that they were supposed to occasionally cough up rainbow shells and also prismatic shards, but that isn't what they're doing. They don't even jump out of the water anymore. Just plain lazy.