Fish Tumours and Tapeworms

In the article I wrote for the 2009 Alberta Guide to Sportfishing Regulations, “On Tumours and Tapeworms”, I discussed why some fish caught by anglers seem diseased. I particularly mentioned skin tumours that are typically found on northern pike, walleye and yellow perch. They are harmless to humans and the fish usually recover. However, they are unsightly and unappetizing; and most anglers release these fish.

I also discussed how anglers sometimes find hard white objects in the meat of whitefish. These are cysts of the tapeworm, Triaenophorous crassus. The adult tapeworm is found only in the digestive tract of the northern pike. However, like many parasites, this tapeworm has a complicated life cycle that involves a crustacean and the lake whitefish. The cysts are not harmful to humans, but like the skin tumours, are unsightly; and they can affect the commercial sale of this fish. It was this concern that prompted pioneer fisheries research biologist R.B. Miller to investigate in the 1950s the life history of the parasite. He determined that control measures would be too costly and detrimental to the environment of the lakes where the parasite occurred.

Parasites and other diseases are a common aspect of living for wild fish. If fish are properly prepared for eating, they are not a problem for people.

So, what’s wrong with that?

About Don Meredith

I am a writer and biologist living in Alberta, Canada. I wrote a monthly column for the Alberta Outdoorsmen magazine, and have published articles for several other magazines.
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