NP are not easy to get to spawn in smaller ponds and lakes. They need flooded vegetation to successfully spawn on. In nature this comes from a lake flooding due to the winter melt and heavy late winter/early spring rains, this doesn't commonly happen in ponds and man made lakes...

One man made lake I fish in PA was drained for dam repair. After a couple years, when the repair was finished they allowed it to fill back to full pool. It filled up all winter covering all the vegetation that had grown while the lake was lowered. The year class the NP produced that year was rather impressive! Otherwise that lake has little to no natural reproduction...