Several trout appeared to have sores/contusions on different parts of their bodies. Mainly near the middle to tail areas. These sores looked like they were rotting or decaying, and I asked a few people and I was told they have never seen these sores before. Trout is an important food source in our village and I'd like to know if these fish are safe to eat and why these marks are appearing. The trout tongue photo was taken a week later. We are still seeing a lot of fish with these kinds of conditions.
Ted Meyers with the Alaska Department of Fish and Game Fish Pathology Lab:
The lesions appear to be traumatic injuries that have been invaded by opportunistic Saprolegnia fungus and assorted bacteria naturally present in the aquatic environment. These lesions may take weeks to progress as in the last photo while lesions in the first photo appear more recent. Injuries could be from predation (birds, mammals, etc) or possibly caused by spawning behavior- digging in the gravel or territorial confrontations with other fish. The photos appear to be of char (Dolly Varden or Arctic) that usually spawn between September and November. Other causes of trauma could occur in fish that have pulled free from fishing gear such as nets. The third photo of the trout tongue is a parasitic copepod of the genus Salmincola. See page 78 of the ADF&G fish disease guide book (below) for details. All the information I have heard and read elsewhere and on LEO suggest warmer temperatures in general have occurred in Alaska this past year. That is one variable that could cause traumatic lesions to more likely become infected but there could be other variables to consider that might result in a greater frequency of initial skin injury such as – is there a greater abundance of fish and/or predators or fishing pressure/gear or change in gear used?
For enlarged images: see our LEO photos page. link
LEO Comment: For more information on fish illnesses see ADF&G Guidebook here: link