Bacterial Infection in 16 Broad Whitefish (Coregonus nasus)

Observation by Dora Leavitt:

Set 5” mesh under the ice net this weekend at the Colville river mouth of Itqilliq river and caught 16 fish that were sickly looking parasite infested white broad fish.

Ted Meyers, State Fish Pathologist with the Alaska Department of Fish and Game, writes:

The skin lesion in the photo is likely caused by a stress-related bacterial infection – possibly trauma initiated- which we have observed before in fall/winter-caught subsistence fish. The internal parasites mentioned could also contribute to the overall physiological stress of the fish, but stress can also be caused by the conditions under the ice - low oxygen environment with little food. It is not unheard of to see an infection like this in more than one fish. Probably common opportunistic bacteria in the environment such as motile Pseudomonas/Aeromonas Gram-negative organisms. The lesion may only be superficial, but generally if fish are properly cooked there are no human health concerns. Parasitic worms may be more of a concerns, but again, adequate cooking should prevail. No samples would be necessary. 11/19/2018

Comments from LEO Editors:

According to Common Diseases of Wild and Cultured Fishes in Alaska, Pseudomonas and Aeromonas are both common types of bacteria in aquatic environments, and are part of the normal microorganisms that live on healthy fish. An infection occurs when the fish is stressed or sick.Water temperatures above 50 degrees Fahrenheit (10 degrees Celsius) create more favorable conditions for this bacteria to thrive. Erica Lujan

We welcome comment from LEO Network members, especially if you have seen similar events or have other insights. This observation has been shared with the Alaska Department of Fish and Game Fish Pathology Laboratory (consult) and with the North Slope Borough Wildlife Department. Mike Brubaker