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

While I was in Ohio I discussed this site with my Nephew and he asked if I had read anything about black spots on Bluegill scales. He found some information that indicates it is a desease. Every Bluegill he caught had the spots starting last summer. I am also concerned because my new pond will be with in a 1/4 mile of his. Please advise.

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.

Theo covered that well. I'm convinced another fish species is good at reducing snails too, provided they are the species of smail that can easily be crushed. (Bill Cody has been to my ponds and says I have two species -- one the fish like and one they do not) That species is the yellow perch. I caught a 15 1/4 inch 2 lb. 1/2 ounce specimen through the ice that passed a snail shell. Since my last planting of yellow perch I have seen a marked decrease in the amount of snails.

I also put up stakes with bright yellow braided line strung in three or four rows around the pond to discourage herons from wading in. The one that kept landing my my pier and I couldn't discourage has strangely disappeared.