Swimming in Circles: A Primer on Whirling Disease

Written by: Nata de Leeuw - Outreach Assistant

Have you noticed the fish behaving strangely lately? Swimming in erratic circles, turning an unhealthy black colour, or even displaying deformities and dying off in mass numbers? If you have, then you have seen the effects of whirling disease first hand!

Whirling disease can be catastrophic to fish populations, and it has recently been discovered in both the Bow and Oldman watersheds. This matters to you if you are an angler, a fish enthusiast, or even just someone who enjoys a tasty trout.

What exactly causes the fish to whirl in circles?

Whirling disease is caused by a parasite that fish can absorb through their skin. The parasite’s spores begin in the soil and are taken up by a specific type of worm. Once inside the intestines of these worms, the spores mature and are released into the water where they are able to infect fish. When an infected fish dies, the spores end up back in the water or the sediment at the bottom of the waterbody and the cycle begins again. So, by simple acts such as cleaning your boots after fishing, you can prevent the spread of whirling disease.

For more information, here is the Alberta Environment and Parks website on whirling disease.

The Montana Water Center also has a great and informative website.

The life cycle of the whirling disease parasite.

The life cycle of the whirling disease parasite.

Will I begin to whirl in circles if I eat an infected fish?

The good news is that humans can’t be infected by whirling disease, so go ahead and eat your catch and swim in the lakes (following local guidelines of course). But this doesn’t mean that we can forget about the problem and move on. If all of the fish in the watershed were killed by whirling disease, there would be no fish left for anglers and the people who make a living off of the local fishery, not to mention predators such as grizzly bears.

What can I do to protect my watershed?

Have you heard of the initiative Clean+Drain+Dry? It works to stop the spread of whirling disease by preventing infected water from being carried from one waterbody to the next. The spores are found in the soil, so stirring up sediment on the bottom of a river can contribute to the spread of the disease in fish. Yet another reason to do your best to keep your wheels out of the water! There is no cure for whirling disease in fish, but we can still work as hard as possible to prevent the disease from spreading.

Follow this link to the Alberta Environment and Parks page on Clean Drain Dry.

If you see a fish that you suspect is infected with whirling disease (remember – swimming in circles, turning black, skeletal deformities) you can report it to the number above.

This video shows the steps to follow to wash your gear:

The situation is far from hopeless, and there are a few common practices you, as a watershed user, can adopt to prevent the spread of whirling disease and help save the fish!

Here are some of them:

  • Clean, Drain, Dry Your Boat
  • Wash all fishing gear (waders, boots, fishing pole, anything else that gets wet)
  • Never move fish, whether live or dead, from one waterbody to another
  • Dispose of fish parts in the garbage, not your garburator, and especially not in lakes or rivers
  • Report any suspected instances of whirling disease that you observe

For news articles on the discovery of whirling disease in our watershed click here.