I’ve found that most high lakes containing copepods have 2 things… big fish, and very picky fish. It seems like the fish aren’t as eager to take a fly or lure because they’re already super well-fed and not as hungry? I was curious if anyone has had any more successful tactics in lakes where these tiny red nutrient balls are present. I’ve still managed to trick some fish with a variety of flies, but it’s usually way more challenging than other high lakes with no copepods present. And the copepods themselves are so tiny, it doesn’t even seem worth it to try and tie a fly that small. I haven’t even seen a midge that small.
Anyway, figured it was worth asking since there’s such a good wealth of knowledge here!
In general rainbow are best able to utilize copepods because they have a finer gill raker structure than other species of trout and char. I have seen populations of westslope cutthroat that feed almost exclusively on copepods, but that is unusual. When rainbow are feeding on copepods they are often out in the middle of the lake where you need a raft to access them.