Pond Boss Forums MANAGING AN EXISTING POND Evaluating and adjusting fish populations Black spots on Bluegills

It is very likely that the black spots are parasitic grubs on the bluegills. Don't panic - if this is the case, it is probably not serious. Here is the first link I could find which discusses his problem:

yellow and black grubs in fish

I imagine there are some threads archived here at the forum which discuss this in further detail, and I know I have seen good photos on-line in articles about the grubs which would help you identify them. Try a web search.

The short summary is: the grubs are the fish stage of a parasite that needs fish, fish-eating birds, and snails to live. You can greatly reduce the incidence of these grubs in your pond (and your nephew's) by 1) discouraging fish-eating birds (many threads on this subject here, see threads on "water turkeys" and herons) and/or 2) stocking redear sunfish which love to eat snails and are great fishing and eating (if you have any affinity for bluegills, you'll like redears; they tend to get a little bigger).

The grubs are not considered harmful to humans, especially when the affected fish is properly cooked.