I recently caught a walleye on Pool 2 of Mississippi River that concerned my boatmate.
The next morning I texted the editor of a prominent fishing publication and he promptly texted me back after viewing the same photo shown above.
“Lymphocystis. Caused by a virus. Most prevalent when walleyes are grouped, as in the spring spawning run. Also more prevalent for some reason in colder water.”
I then looked up lymphocystis on the MN DNR web page. Although I learned a few more facts, I was no closer to knowing what caused the condition. Sure, a virus, but what are the conditions that lead to infection?
Google—which can be a rabbit hole when researching medical conditions, especially of the human-kind—turned up a number of various links. I spent a couple hours scanning web pages and academic research paper abstracts, trying to solve the mystery.
For example, I learned the following from a Vermont Fish & Wildlife Department “fact sheet”:
“In walleye populations, these diseases are more common in sexually mature adults. Infections have been observed throughout the year but occur at a higher rate in early spring, during the walleye’s spawning season. Walleyes congregate on their spawning grounds, and the virus spreads from fish to fish through physical contact or water transmission.”
Sounds like a walleye STD to me.
And, from the Pennsylvania Fish & Boat Commission:
‘It [lymphpocystis] is characterized by raised, rough, nodular masses of generally light colored, somewhat opalescent white, gray or cream-colored tissues that superficially resemble warts. Larger, more developed lesions may have areas of pinkish or reddish coloration due to blood vessels in the infected tissues. These lesions are usually external, located on the skin or the fins, but occasionally they are found internally along the gut and in the heart and other internal organs. Massive replication of the virus within the walleye skin cell causes the size of the infected cell to increase in size dramatically. Eventually these cells burst or slough off, releasing the virus and leaving a light colored scar. Lymphocystis usually appears in the spring and reaches maximum development in the summer. In the fall and winter the lesions gradually disappear. Although walleye are most susceptible to the lymphocystis virus, perches, sauger, darters, sunfishes, basses, bluegill and crappie can also develop the infection.”
And from the MN B.A.S.S. Nation web site, always a leader in cutting-edge walleye information:
“A 1976 Canadian study examined 50 tumors which were thought to be lymphocystis and found twice as many dermal sarcomas as lymphocystis tumors. Examination with a magnifying glass will usually separate the two diseases. Lymphocystis tumors are composed of a few grossly enlarged cells. Dermal sarcomas consist of irregularly shaped but normal-sized cells. Both diseases can infect the same fish concurrently and, in some cases, both diseases have been seen in the same tumor. Yet they are caused by distinctively different viruses; two viruses which have not been found to exist together in the same cell. At least 65 species of freshwater and saltwater fish are known to contract lymphocystis. Lymphocystis and dermal sarcomas are not generally fatal to the infected fish. Practically all will recover from their infections. Anglers need not worry if these growths are seen on their walleye. The flesh will be unharmed and neither disease can be transmitted to humans.”
However, a couple things emerge from my cursory research via a very dubious medium (the interwebs):
- Lymphocystis is not typically fatal in walleyes.
- It is not contagious to humans.
And the $64,000 Question: Can you safely eat walleyes with warts?
During legal season and within your state regulations, probably yes.
If you are hungry enough, an emphatic yes. Again, the meat, not the warts.