Pond Boss Forums INTRO Questions & Observations Dead Bluegill

Have a client near Athens, GA who has been losing bluegill (hundreds of them) for the past few weeks. Here is some background:

-Has a Vertex Air 3
-Receives runoff from the watershed which has had been limned and fertilized and he also pumps in some well water with an inverter that adds oxygen to the well water
- Lake was limned two years ago and has not been fertilized in two years (always green)
-Visibility was 10” yesterday when we shocked the lake
-While shocking the lake, he has thousands of threadfin shad, limited bluegill (they have been dying), redear, and some great bass. Also, it seems that the bluegill did not have a very successful spawn, or they either died first when all this started
-He has turned his feeders off since the bluegill have began to die, about three weeks ago, but he was feeding 75-100 pounds of food a week since the bluegill were eating it all.
-He has an oxygen meter and the oxygen has been fine
-As I was shocking the lake, there was a couple of bluegill that were lethargic and swimming just below the water surface. However they were still able to swim away when we got close to them.
-Lake is about three 2.5 acres

The main thing is, I took the otoliths out of a bass and one bluegill. When I cut the bluegill open its liver was brownish-gray and there was this bubble with some fluid in it and I could somewhat see through it. See the picture at the following link, it's at the tip of the knife blade (Link to BG Necropsy Photo) Anyway, it’s been a long time since I have cut open any bluegill and I do not remember seeing anything like this. Is it something that could cause stress and eventually death or is nothing to worry about? Unfortunately I did not cut the bluegill open until we were done counting the fish, etc. so I had no other fish to cut open and look at. Anyway, its only bluegill he has been losing. Just wondering if anybody has any ideas, I know it’s a lot of food he has been feeding and a very dense bloom but still confused about the bluegill I cut open.

Matt,
That bubble the fish's gall bladder. It's full of bile.
Since the bluegill you dissected was mature, this problem must be recent, rather than ongoing (If the water or the pond were the problem, bluegill wouldn't be so active and prolific to this point).
That makes the problem related directly to the bluegill. That narrows it down further.
Since you see no symptoms of disease, such as bruises, infections, etc., that likely rules out bacterial infections due to crowding.
That narrows it down to two other things...toxins or virus.
I bet it has something to do with the feed.
Since the landowner has a history of feeding lots of feed, and since Athens, Georgia has recently received some rain, my bet is that the feed has become moist, leading to molding, which leads to aflatoxins, which leads to dead bluegill.
Check the feed and see if it is moldy.

http://edis.ifas.ufl.edu/BODY_FA095

Signs of Aflatoxicosis in Fish
Initial findings associated with aflatoxicosis include pale gills, impaired blood clotting, anemia, poor growth rates or lack of weight gain. Prolonged feeding of low concentrations of AFB1 causes liver tumors, which appear as pale yellow lesions and which can spread to the kidney. Increases in mortality (higher numbers of dead fish) may also be observed.
Aflatoxins can cause disease indirectly through their effects on essential nutrients in the diet. For example, fat soluble antioxidants, such as vitamin A, and water soluble antioxidants and vitamins, such as vitamin C (necessary for immune function) and thiamin (necessary for metabolic and nervous function), in feeds can be destroyed by these toxins. Hence, it is not surprising that aflatoxins depress the immune system, making fish more susceptible to bacterial, viral or parasitic diseases. These subtle effects often go unnoticed and profits are lost due to decreased efficiency in production, such as slow growth, reduced weights of the finished product, an increase in the amount of feed needed to reach market weight, and increased medical costs.

Thanks for the help Mr. Lusk and Mr. West

Bob, anyone else. Shanun Banks you out there? The food is kept in cooled barn, nice setup, so doubt it coud be moldy food. Remember I have a published paper on aflatoxin so I understand that one but do not believe that is the cause. The liver was light brown color (not reddish) if that means anything. Like Matt said thanks again.

I would still check the feed for mold. Look in the feeders, check some full bags and make doubly sure.
Second, has anyone looked inside the stomach of any of these dead fish? I have seen fire ants cause bluegill death on several occasions. Rain, inundate some land with fire ant mounds, ants floats en masse, bluegill eat them...and die with guts packed full of fire ants.
If none of the above, I would find a fish pathologist, send in some live fish with symptoms and find out. There may be a virus out there that we need to know about.