Ask an expert: Is this fish safe to eat?

by Editorial Staff | February 25, 2021
fish with mound, flesh eating disease, walleye

Q: I was walleye fishing on a kettle lake between Lake Joseph and Georgian Bay last summer and after we landed a few fish I noticed some kind of flesh-eating disease on the right cheek of one of the fish. Otherwise, it was very healthy looking, but I have never seen this before. Have you? What is it? Is it safe to eat? If I catch one like this again, am I to let it go, or is it a sign of a bigger problem and should be destroyed?

– Matt Klymenko, MacTier

A: OFAH fisheries biologist Adam Weir responds: I touched base with Dr. Véronique LePage, a fish pathologist from the University of Guelph, and the quality of the images did not allow her to confirm or deny the presence of gill copepods/gill lice, but mentioned that the eroded operculum (gill cover) can be due to old or ongoing gill disease.

Possible causes

In Ontario this is most commonly attributed to bacterial gill disease, nodular gill disease, or columnar is, or maybe a result of other things like genetics, trauma, etc. It is possible that this fish was compromised from previous disease, leaving it with a shortened operculum. However, there’s nothing really conclusive from just the image.

Consumption recommendation

To answer your other questions, the fish is most likely safe to eat. If you catch one like this again, and are legally allowed to keep it, refer to the Guide to Eating Ontario Fish for consumption recommendations. The issue is likely not part of a bigger problem, and the fish should not be destroyed. It is illegal to abandon fish or permit the flesh to spoil, if the fish is suitable for human consumption.

Dr. Véronique LePage
Fisheries Pathologist at the University of Guelph
(via Ontario Federation of Anglers and Hunters Fisheries Biologist Adam Weir)

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Originally published in Ontario OUT of DOORS’ 2020 Fishing Annual.

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  1. Bill Albert wrote: The comment “It is illegal to abandon fish or permit the flesh to spoil, if the fish is suitable for human consumption.” raises another interesting question. What happens when a fish is caught that is outside of the slot size and must be released however it’s obvious that the fish will not survive. It’s against the law to allow it to spoil but it’s also against the law to keep it. What does an angler do?
    • Alesha Howran wrote: Thank you for your question. We reached out to our OFAH fisheries biologist and here’s what we learned. Section 12 of the Ontario Fishery Regulations (Release of Fish) states: A person, other than a person fishing under a commercial fishing licence, who catches a fish, other than an invasive species, the retention or possession of which is prohibited by these Regulations, shall immediately return the fish to the waters from which it was caught and, if the fish is alive, release it in a manner that causes the least harm to that fish. The regulations provide flexibility in terms of the physical condition of the fish, and further, provide wording on releasing the fish in a way that reduces harm if it’s alive. Therefore, regardless of the condition of the fish, if an angler is legally responsible for returning the fish to the waters it came from, they must follow the rules and regulations for doing so. Under these circumstances, these actions wouldn’t be considered spoilage or abandonment. Additionally, if this weren’t the case and anglers were able to keep injured fish that they would otherwise be required to release by regulation, the rules for releasing fish would be unenforceable; anglers could claim that the fish wouldn’t survive as a reason to keep it.