An infection or abnormal growth was captured on the lower left jaw of the fish.
Follow up comment on 5-12-21 by Jeremy Fitka:
I did not come across any other fish with the tumor, nor heard of anyone else catching one with similar signs of it while we were spring ice fishing.
Jayde Ferguson, Pathologist with the Alaska Department of Fish and Game, writes:
This does look like an abnormal growth, so a neoplasm of the mandible. It’s likely an ameloblastoma, which is a tumor of odontogenic epithelium involving ameloblasts (the outside portion) of developing teeth. There are a number of factors that may lead to neoplasia, such as viruses, carcinogens, repeated physical trauma, hormones, age, sex, genetic predisposition, and immunocompetence. Generally there is not a direct human health concern unless these become frequent in a fish population, which may indicate the presence of a carcinogen in the environment.
As Jayde describes, this looks like a tumor in the teeth forming tissue of the fish. There are several other isolated incidents of tumors on fish that have been reported to LEO. In the nearby community of Pilot Station, fishers caught a king salmon with a tumor in the connective tissue/muscle. In Selawik, fishers caught a whitefish with a tumor on the dorsal fin. In Unalaska, a rockfish was caught with an X Cell tumor that is the result of a parasitic infection. Although these growths look unappealing, they do not pose a human health risk. Tumors on fish are usually a rare event, affecting only one fish in several thousand.