Case of the Mystery Burbot
By Ella Swan, Lake Windermere Ambassador’s Summer Student
You never know what you might see out in Lake Windermere if you take the time to look beneath the surface. On July 8th, some of what is usually “beneath the surface” came to the surface, getting us to question what might be happening in this watery environment.
During the week of July 8th while the Lake Windermere Ambassadors staff and volunteer were taking water samples at the south end of the lake, we made a startling discovery. There was a dead fish floating on the surface of the water. And not just any fish, but a burbot, a species which has experienced significant declines in Lake Windermere[1] Read on to learn more about the burbot of Lake Windermere and what might have happened to this particular fellow.
Burbot, also known as Ling Cod, are the only species of freshwater cod. They make their home in cold lakes throughout northern North America, Europe and Asia. As fish go, they are fairly odd looking. They look like a cross between an eel and a catfish. With their greenish mottled complexion, beard-like single whisker and wide gaping mouth the burbot can be a startling sight to fishermen. They are bottom dwellers who feed in the night on everything from fish smaller than them to frogs and insects. During the daytime, they hide in extensive burrows that they build in the lake sediment. Another behaviour unique to burbot is that they are the only fish in this area that spawns during the winter under the ice. They were historically a key food source for the First Nations peoples.
Lake Windermere may be experiencing conditions that are less than ideal for burbot. A report by Paragamian et al (2000) reported significant declines in this fish in the Columbia River system, including Lake Windermere. In a 2007 survey of Lake Windermere, none were found and it was feared they were gone for good. As a more recent indication of the numbers of burbot, a local fisherman said: “There are ling in Lake Windermere but not as many as there used to be. Few, but they do exist here. When dams began appearing such as Mica (Revelstoke), ling began moving to larger and deeper waters. When non-native species such as bass were introduced here, the ling began competing with such species causing a decline in their numbers.”
As reported in the 2008 report on Fish and Wildlife in Lake Windermere (Interior Reforestation, Ltd.) temperature is likely a cause. Burbot prefer temperatures that are cooler than Lake Windermere, which has been getting warmer in the summer. Competition from invasive species like bass and northern pike minnows may also have sent burbot on the decline. BC fishing regulations restrict this fishery to “catch and release only” to protect the numbers that are left.
What happened with the fish we saw?
It is thought that the burbot move out of Lake Windermere into colder waters for the summer and come back to spawn during the winter. So why did we see one and why was it dead?
There are a few possible explanations. The fish may not have died in the location that we found it. The burbot could have been living in the Columbia Wetlands upstream, died, then floated into the lake. It may have simply died of old age (the burbot we saw was about 1 to 1.5 feet long). Or it could have mistakenly come into the lake where it met waters that were too warm, which can cause stress and disease. One disease that burbot are susceptible to is Entric Redmouth Disease, which causes the fish to hemorrhage around its mouth and gills and internal organs. This is a very distant possibility.
We will never know the exact cause of that one burbot’s death, but we do know some of the challenges burbot face in our area: competition from non-native species like Largemouth Bass, habitat destruction, and raised water temperatures in summer.
[1] Windermere Lake Foreshore Fish and Wildlife Habitat Assessment. Sept 2008. Interior Reforestation Co. Ltd