6b514bce_ter_Fish___Minnesota_Sea_Grant__Symptom
[Parasite] FISH LOUSE (Argulus spp.) [Type] copepod [Description] Rarely seen; up to ½ inch; often leaves fish after removed from water. Pierces skin, destroying fish's mucous coat. Secondary infection from bacteria or fungus can result. [Edible] Yes [Recommendation] Clean fish and prepare as usual [Symptom] 
Bloody area under scales. Louse-like organism, resembling miniature turtle under scales
Parasites of Freshwater Fish | Minnesota Sea Grant
Symptom