The Shuswap Lake system in the Fraser is renowned for its rainbows. Lots of them, and large. There were some who believed that the cyclic dominance in that system was maintained by trout predation. Maybe. But also of interest is that dominant run (1 in 4) provided the food to drive the trout population. In the other three years they didn't have enough fish to support themselves.

The Gerrard Rainbow (a huge resident Kamloops/redband) got that way gorging on kokanee. Then, mysids were introduced and they crashed the kokanee. Experiments were done to fertilize the lake to provide food for the kokanee. It worked. They rebounded quickly. It took 5 more years for a signal to show up in the trout. Sometimes, it takes time.