Columnaris (<i>Columnaris</i>)


White - grey cottonwool tufts
White - grey cottonwool-like tufts appear on fins.
White - grey cottonwool tufts.
Whitish-grey cottonwool-like tufts grow on the skin.
Skin lesions
Lots of small lesions appear on the skin
Yellow-orange ulcers
Skin shows ulcerated lesions of distinctive yellow-orange colour.
Grey patches, faded look body
Grey or faded looking patches are evident on the anterior portion of the fish.
Saddle-like dorsal growth
Saddle-like growth from dorsal fin to body.
Temperature elevated
Temperature is higher than the normal for these fish, or usual temperature
Distal part of fins lose colour
Upper parts of fins lose their natural colour.
Fins frayed or ragged
Fins look as if they are rotting away, giving eroded appearance.
Gills swollen
Gills show obvious swelling.
Ulcers - irregular
Irregular shaped ulcers are evident on the skin.
White necrotic lesions - skin
The skin shows white necrotic lesions.
Yellow-brown growth on mouth
Yellow-brown growth on mouth.
Gills have excess mucous
Obvious slimy mucous is oozing from the gills of the fish.
Milky patches on fins
Cloudy patches are scattered over the fin tissue.
Respiration rapid
Fish is breathing very fast, much faster than is normal.
Ulcers - circular
Ulcer with circular shape.
Grey/white spot around head.
Around the head area is a large grey or white spot.
Reluctant to feed
Fish comes to eat but with evident lack of appetite.
Sits on bottom
Fish sits still in upright position, on the bottom of tank or pond.
Breathing at surface
Fish stays at surface usually at an inclined angle and breathes or sucks air.
Gills brown/red
Gills have a dark brown or dark red colouration.
Hanging at surface
Fish stays at water surface all the time.
Listless and lethargic
Fish moves very lazily in water, much less than normal, lacks interest.
Milky patches
Grey milky coloured patches are evident on skin.


Caused by infection with Flexibacter columnaris, Flexibacter maritimus aka Cytophaga columnaris, & Bacillus columnaris. Has a distinctive gliding motion under a microscope.
Species especially affected are:Channel Catfish, Eels, Salmonids, in Aquaria Black Mollies.
Flexibacter columnaris, has been identified as the causative organism of 'Black patch necrosis'

in Dover sole in Scotland. Other species including Sea Bream, as well as Shellfish, have been described by other authors. 


Can be treated and eliminated if instructions are followed. May reach higher levels of mortality at elevated temperatures. The treatments are primarily related to freshwater infestations.

DNA and RNA diagnostic references

Use of suppressive subtractive hybridization to identify Flavobacterium columnare DNA sequences not shared by Flavobacterium johnsoniae. 

From Letters in applied Microbiology Feb. 2008 

O. Olivares-Fuster and C.R. Arias 

Department of Fisheries and Allied Aquacultures, Auburn University,
Auburn, AL,


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Dr. Chacko, Jim
Unity College of Maine
Fish Patholgy Dept.

Dr Prescott, Shawn
Fish Disease Dolau Ltd


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