Growing up we would fish the evening, camp, and then fish the next morning and then head home before noon. That was usually a fun trip, and designed to just skip the poor fishing in the middle of the day.

However, we did learn the lesson that turtles will certainly chomp on fish that are left overnight on a stringer. When we had a mix of catfish and bass on the stringer, they seemed to prefer chomping on the catfish. (I assume because it is easier to get a bit of meat off of a non-scaled fish?)

Most of the time, the fish with only one bite taken were still alive the next day. However, we NEVER caught a fish that exhibited a turtle bite.

The experts on the forum say that turtles will not attack healthy gamefish, and that certainly aligns with my non-expert observations. However, I have seen turtles working on severely disabled or dead fish.

I think I would be OK with a few turtles in most situations, especially if they would clean up the dead and dying fish. If that helps the pond escape the notice of cormorants looking for an easy meal, then the turtles might be a large net benefit.