The Columbia River is under attack by an invader that is not visible to the naked eye. In December of 2023, whirling disease was detected in the headwaters of the Columbia River watershed. The disease is caused by a parasite which can infect trout and salmon. The disease is not harmful to humans, but it can cause up to a 90 per cent mortality rate in juvenile fish.
This disease could have major impacts on the Columbia River. In the worst-case scenario, enough juvenile fish may die that fish populations collapse. Over time, the disease could eventually move into the Kootenay, Okanagan, and Similkameen systems. In some cases, this could bring fish stocks to the point of extinction; without juvenile recruitment, trout and salmon populations may plummet.
This is bad news for wildlife and those who rely on these fish as a food source. Our rivers, once known for their large trout and salmon, will fall quiet as an ecosystem slowly dies off.
The disease is spread by the spores of a parasite being consumed by an aquatic worm (tubifex tubifex). The spores then grow to a free-swimming life stage, known as TAMs (triactinomyxons). After reaching this stage, fish either eat the worms or the TAMs infect the fish through their skin. Once within the fish, the parasites then feed on the fish's cartilage until new spores are produced.
This process affects the fish's central nervous system and can cause symptoms like spinal deformity, shortened snout, incomplete gill plate, and discoloration of the tail. These symptoms are not always all present, but one of the best indicators is the deformed tail which makes the fish swim in a whirling pattern, giving rise to the name “whirling disease.”
Currently, the disease has only been detected in the headwaters of the Columbia watershed within Yoho National Park and at the park's border on the Kicking Horse River. Currently, the provincial and federal governments are working to slow the spread of the disease and prevent it from spreading to other waterbodies. One way they have worked to combat the disease is by shutting down watercraft use and fishing within Yoho and Kootenay National Parks.
According to Shelley Humphries, a Parks Canada Aquatic Specialist for Yoho and Kootenay National Parks, “We think the transfer of the disease into Yoho is new, so we are waiting to see the results from the monitoring inside and outside the park.”
This will tell us if the parasite is widespread or still isolated to the park’s lakes and streams.
Humphries also explained a few of the techniques her team is using to monitor the spread. The team deployed sentinel cages filled with sterile rainbow trout into the Kootenay River and Kicking Horse River. By monitoring the fish in these cages, they can detect if the parasite is effectively spreading.
Another technique is called E-DNA, which involves collecting water samples to then testing them for the presence of DNA left behind by the parasite.
Lastly, they use electrofishing to shock the water and momentarily stun the juvenile fish for sampling. Unfortunately, at the time of this article the results from the tests are not in yet. These samples need to be held at -80 C until they can be lab tested and then analyzed, which is a time consuming task. All we can do is eagerly wait for the results to come back.
Even though there is no cure for whirling disease, we can still take actions to slow its spread. In May of 2024, the B.C. government implemented new regulations including a ban on transporting watercraft with a drain plug installed. Boaters must clean, drain, and dry their watercraft before moving to a new waterbody. It is recommended that boaters wait 24 hours before placing their watercraft in a new waterbody.
Aside from dirty boats, the parasite can be carried on almost any equipment used in the water. Thus, people who recreate on the water can do their part by cleaning and sanitizing their equipment before use in a new waterbody.
Whirling disease poses a huge threat to the Columbia watershed. The best defence we have against the disease is to follow regulations when moving equipment and to report sightings of fish showing the symptoms. This disease will not go away which means the survival of B.C.’s fish populations is in our hands, so everyone needs to do their part by cleaning their equipment, so we don’t repeat this in other areas of the province.
Since the writing of this article, whirling disease has been discovered in the south end of Kootenay Lake. This is a good example of how fast the disease can spread if we don’t take action.
Matthew Watts is a student in the Recreation, Fish and Wildlife program at Castlegar’s Selkirk College.
