by Erling Friis-Baastad
‘If they haven’t seen a burbot before, anglers might be unnerved,” says territorial fisheries biologist Oliver Barker. “Burbot don’t look like other fish they catch here. They’re long and slimy and move in a way that resembles eels.
However unnerving, the homely cod is starting to receive its overdue share of scientific respect.
Traditionally, among Yukon game fish, lake trout have garnered most of the praise and scientific attention. Even the gorgeous, iconic grayling barely registered in earlier fisheries management studies. That’s changed recently.
“New blood” on staff and expanding priorities were reflected in Environment Yukon’s Status of Yukon Fisheries 2010 report, says Barker. The report identified some neglected species. Among them is the only known freshwater cod, a top-of-the-food-chain carnivore called burbot. It is also known by its scientific name, Lota lota, or in some areas as eelpout, lawyer, mariah, loche and ling cod (though it’s not closely related to the saltwater fish of that name).
Whatever we might think of their looks and feel, burbot are “fascinating,” Barker says. First of all, how did they become the only freshwater cod? Scientists suspect that at some point in ancient evolutionary history, proto-burbot swam into a river outlet from the sea and found that the brackish water was rich in nutrients. Afterwards, they moved further inland, finally adapting to, and then requiring, freshwater.
They are also the only Yukon fish that spawn in winter. Males arrive at the breeding grounds first. When the females arrive, they all coalesce into massive “burbot balls” to release sperm and eggs. A large burbot could lay about a million eggs, says Barker. The resulting baby fish just swim off and develop on their own.
The young feed mostly on invertebrates, insects and crustaceans, but as they grow they begin eating other fish. Last winter, a Yukon angler caught a nine-kilo burbot, says the scientist. The whopping cannibal still had the remains of another largish burbot protruding from its mouth.
While sporting visitors fall prey to colourful photos of lake trout so huge they sag over the arms of the proud anglers who pose with them, locals know that burbot are nothing to be sneezed at. Like saltwater cod, burbot have flaky, white meat and large livers rich in vitamins, especially D and A, and they can provide a memorable wintertime angling adventure. Therein lies the rub. Burbot are easily fished from lakes that are handy to towns and cities. Alaska has experienced declining burbot populations in the most popular lakes, and there are anecdotal reports of diminishing catches in some of the more heavily-fished lakes of the Yukon.
There’s a big data gap in our knowledge of burbot, says Barker. So how can scientists go about filling that gap without stressing the fish with unnecessary intrusions and handling? Last fall they launched the first step of a “mark and capture event” when they lowered traps into Little Fox Lake just off the North Klondike Highway, south of Braeburn.
The method they settled on is simple and elegant. One would have to catch a whole lot of fish or drain a lake to count its burbot population. So the researchers trap some fish in the fall, tag them, then release them to mingle with the general population until spring. Then the traps are laid out again, fish caught and measured, tags counted, and some simple math performed.
For a hypothetical instance, says Barker, “if we catch 100 fish and mark them and let them go to mix in with the unknown number in the general population, then come back in the spring and catch 100 fish again and we notice that half of them have tags, then ... it seems as though, in our first capture situation, we tagged half of the fish. So we know there are about 200 fish total in the general population.”
That retrapping will take place for the first time at Little Fox Lake in May, when the ice goes off the water, so the scientists aren’t sure of the outcome of their first test. Barker is sanguine that the less-intrusive mark and count method will serve both the scientists and the fish. After deciding to conduct a burbot study, fisheries personnel researched methods used in other jurisdictions before attempting them here.
“The traps are very easy to use,” says Barker. “They’re kind to burbot. They come up quite lively and swim off again with a lot of vigour. Part of the method I quite like is the burbot don’t show ill effects from being inside the trap.” As well, other species, such as lake trout, don’t get caught along with burbot.
The traps, which resemble commercial crab traps, are lowered into the lake, attached to a cord which is tied to a float. The traps are left overnight. Night is when burbot, unlike other Yukon game fish, are most active. The preferred bait is deep-frozen, salted smelt. “We discovered, very definitely, burbot hate hot dogs. They seemed like the ideal cheap bait, but they didn’t work at all,” says Barker, laughing.
Fall and spring were chosen as “trapping seasons” because the fish are generally scattered throughout the lake rather than in breeding balls, and the surface is ice-free.
When the traps are returned to Little Fox in May, the scientists should have a good idea just how suitable their gear is for the Yukon, how feasible the method of counting is for the territory and how many years the trapping should continue. If the results are as good as expected, Barker and his colleagues will turn their attention to other popular burbot lakes in the territory.
We don’t have any indication that there are burbot populations that have collapsed in the Yukon, but that’s certainly something we want to avoid,” says Barker.
“In these areas where there might be a concern this (mark and capture method) will back us up, help manage burbot and help ensure there will be burbot forever.”
Meanwhile, says Barker, if anglers catch any tagged burbot, they can choose to keep or release them, but he would appreciate them giving fisheries a call at (867) 667-5199, or sending a message to fisheries@gov.yk.ca
This column is co-ordinated by the Yukon Research Centre with major financial support from Environment Yukon and Yukon College. The articles are archived at www.taiga.net/yourYukon.