Walleye dermal sarcoma is a benign tumour caused by a virus that develops from the deep layer of the fish’s skin (dermis).

Wildlife at risk

The disease is observed only in adult walleye and sauger.

Signs of the disease's presence

Walleye and sauger have tumours of 2 to 5 mm in diameter. These tumours develop from the dermis. The growths are white, firm and rubbery. They are composed of several rounded lobes. The tumour is generally not fatal, except in cases of complications through secondary infections.

Two other diseases that can cause growths in fish are the lymphocystosis and lymphosarcoma.

Transmission and persistence in the environment

The disease is transmitted through direct contact between fish, particularly during spawning gatherings. At this point, the infectious cells break and release a great quantity of virus.

Protection and prevention

Risk for wildlife health

This tumour does not appear to have a significant impact on walleye and sauger populations.

Risk for human health

Walleye dermal sarcoma cannot be transmitted to humans. Although the growths reduce the interest and value of the catches for sport and commercial fishing, the fish remain edible. It is still recommended that all visible growths be manually removed before the fish is completely cooked. Adopting some safe practices when preparing and cooking wild fish remains relevant.

Surveillance and control

Walleye dermal sarcoma is known to be present in Québec. You do not have to report suspicious fish. To stop transmission, do not discard any unused fish parts in the water. Instead, put them in the garbage or burn them.

Last update: January 8, 2024


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