Black Spot
Columnaris Disease
Endogenous Pigment
Fibromas and
Fibrosarcomas
Gas Bubble Disease
Hemorrhagic Disease
Leech Infestation
Lymphocystis
Lymphosarcoma
Mollusc and
Crustacean Infestation
Muscle Atrophy
Muscle Necrosis
Myxosporidia
Red Plague
Saprolegniasis
Tail Rot
Tapeworm Cysts
Walleye Dermal Sarcoma
White Spot

Name of Disease	Probable Cause	Appearance	Species of Fish Affected	More Info
Hemorrhagic disease	bacterial	hemorrages under skin, on internal organs swollen abdomen, bulging eyes	fish found in warm water; brown trout
Columnaris disease	bacterial	lesions on head, back and gills	most freshwater species
Red plague	bacterial	lesions (small blisters, hemorrages and ulcers) of the skin, commonly found at bast of fins	freshwater (wild and captive)
Tail rot	bacterial	lesions usually confined to skin muscles and fins; fins misshapen and ragged looking	trout; freshwater species (northern SK)
Saprolegniasis	fungal	grey-white patches on skin	trout, white suckers
Tapeworm cysts	parasitic, larval form of tapeworm	cysts in muscle and internal organs	most fish species
Black spot	parasitic, larval form of fluke	small, poppy seed-sized cysts in muscle and skin	yellow perch, white and longnose sucker, brook trout, cisco, sauger, northern pike, walleye; any species
Myxosporidia	protozoan parasite Myxosporidian	hemorrhage on gills and in skin; perch, nodules in muscle	yellow perch, brook trout
White spot	protozoan parasite Ichthyophthirius	small white spots on the skin and gills	yellow perch, brook trout, smallmouth bass, white sucker, rainbow trout
Leech infestation	attachment of leeches	skin	most freshwater species
Mollusc and Crustacean infestation	attachment of molluscs and crustaceans	molluscs attach to gills, crustaceans cause ulcers of skin; fins can be affected	any fish species
Lymphocystis	viral	invasion of skin by virus, cyst-like structures; gills	walleye
Fibromas and fibrosarcomas	unknown in most fish; walleye, retrovirus	both tumors appear as loosely attached or firmly anchored raised masses on body, head, fins or gills; may invade muscle	northern pike and yellow perch
Lymphosarcoma	viral	skin or muscle tumors; can spread to liver, kidney, spleen and thymus	northern pike
Walleye dermal sarcoma	viral	tumors similar in appearance to fibrosarcomas; found on skin surface	walleye
Gas bubble disease	sudden change in gas content of water; can be due to temperature change	blisters on gills and under scales	any fish species
Muscle atrophy	unconfirmed	fish are abnormally thin for their length and muscle may be gelatinous or have a chalky material speckled throughout	many fish species
Muscle necrosis	unconfirmed	flesh is dark brown, fibrous and may appear as scar tissue (dense and white)	walleye
Endogenous pigment	ingestion of colored pigments	discoloration of muscle (green or orange)	any foraging fish; most common in yellow perch and trout species
Trauma	varied	cuts, scrapes, swelling, discoloration of the fish	any species