black spot disease on trout

[EatSleepFish]

i have been fishing a local creek, and started noticing that alot of the medium sized (6-7 inch) brookies had quite a few black spots on them. I know this is common in sunfish, but trout? are they eating infected snails or something?

[DEADhead]

Here's a synopsis of Black Spot disease from the Jan/Feb issue of the Conservation Volunteer

Black Spot Disease , Uvulifer ambloplitis

Have you ever caught a fish that looked like someone had sprinkled it with coarse-ground pepper? You were likely looking at black spot disease, caused by the larval stage of certain flukes that live as adults in fish-eating birds. Any fish can become infected. The most frequently infected are sunfish, yellow perch, northern pike, bass, and other fish that live in shallow water and vegetated areas where birds and snails are found.

Life Cycle: 1 The adult fluke lives in the digestive tract of fish-eating birds, typically kingfishers or herons. It produces eggs, which pass from the bird in its droppings. The eggs hatch in water, liberating larvae called miracidia that swim around until they encounter a snail.

2 After digging their way into the snail, the miracidia form mother sporocysts. Mother sporocysts produce sporocysts that invade the snail?s liver. In about six weeks, each sporocyst produces another form called a cercaria.

3 Cercariae emerge from the snail into the water. They seek out a fish and penetrate its flesh, forming cysts just under the skin and in the flesh.

4 If a bird eats infected fish, the parasites leave the cysts and mature in the digestive tract of the bird, starting the cycle again.

Effects on Fish: Black spot is rarely fatal to fish. A heavy infection may make a fry?s eyes bulge. If heavily infected fish live in stressful conditions (poor nutrition, injury, crowding, etc.), they could die.

Effects on People: Black spot disease is not harmful to humans. However, you may find the spots unappetizing. Your best bet is simply to remove the skin and cysts in the flesh before cooking the fish.