Burbot boom may be bust for lake trout

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LANSING — Burbot, fish native to the Great Lakes, are slimy, big-mouthed bottom feeders.
And they’re threatened in many parts of the world, according to Martin Stapanian, a research ecologist for the U.S. Geological Survey’s Lake Erie Biological Station. That reality makes the story of the species’ Great Lakes collapse and recovery even sweeter.
But new research shows that the burbot revival could hamper a multi-million dollar effort to restore lake trout, another Great Lakes native.
In the 1950s, commercial fishing and the invasive sea lamprey wiped out Lake Michigan’s lake trout. Burbot populations dropped drastically, too, but the species hung on in small numbers. Biologists say that’s at least partly because burbot were never popular among for commercial fishers.
The small commercial burbot harvest doesn’t mean that few burbot were in the lake.
“There were a lot more burbot than that in the lake,” said Randy Eshenroder, a science adviser with the Great Lakes Fishery Commission in Ann Arbor.
The lack of commercial interest may have helped burbot survive tough times, but it’s also gotten the fish in trouble around the world.
“The overall lack of commercial and sport interest in burbot has undoubtedly contributed to its being ignored or regarded as a ‘trash’ fish by some management agencies,” according to a report that Stapanian co-authored.
Burbot populations were listed as “secure” in only four of 24 Eurasian countries surveyed in the report, and in 10 of the 25 U.S. states.
In the Great Lakes, management apathy toward burbot has played out much differently.
The lakes’ burbot couldn’t have rebounded without the massive sea lamprey control program coordinated by the commission, said Stapanian, who is based in Sandusky, Ohio. The drop in invasive alewives, which feed on burbot larvae, was also essential.
Even without a stocking program, burbot have recovered in all of the lakes except Ontario, where alewives remain too plentiful, Stapanian said.
That’s not the case for other Great Lakes natives.
Since 1965, managers have stocked Lake Michigan with an average of 2.7 million lake trout per year in an effort to reestablish a naturally reproducing population. Since 1986, many of those fish were stocked in the lake’s two lake trout refuges where fishing is off limits.
The refuges are relatively shallow and have rocky bottoms that were historically fruitful spawning sites. Biologists hope that the fish will return to the refuges and lay eggs once they’re fully grown.
So far, it hasn’t worked very well. Biologists aren’t sure why, but they often blame invasive species like sea lamprey and alewives.
But a study published this year in of the Journal of Great Lakes Research shows that the resurging burbot may have something to do with it.
One lake trout refuge sits between the Leelanau Peninsula and Beaver Island, and people are particularly interested in getting lake trout to spawn there, said Greg Jacobs, a biologist with the U.S. Geological Survey’s Great Lakes Science Center in Ann Arbor.
“So we wanted to get a good idea on whether burbot might have an effect on that,” he said.
To do that, scientists checked the stomachs of 95 burbot caught in northern Lake Michigan from 2006 to 2008. They found the effect they were looking for in burbot caught near lake trout stocking sites: Burbot eat small lake trout.
It’s not yet clear how big of a drain burbot are on lake trout stocking because no one is sure how many burbot hang out around the lake trout refuge, Jacobs said.
But studies in other lakes and other sections of Lake Michigan give scientists a range of how many might live in a given area.
If northern Lake Michigan burbot are on the high end of that range, it may be lights-out for the refuge’s lake trout.
“It could be entirely possible that they could eat all of the lake trout that are stocked out there within 30 days,” Jacobs said. That’s about how long would take for a lake trout to figure out how to escape the burbot.
Any stocked fish are an easy target for predators already in the lake, Eshenroder said. “They’re coming out of hatcheries, they’re naive, kind of bewildered, you might say. They’re disoriented.”
Perhaps there aren’t enough burbot to eat all the lake trout. But even if there are only enough to wipe out a quarter of the stocked fish, that would impede lake trout restoration, Jacobs said.
Biologists need more studies of burbot density and behavior before they can be sure how big that impediment is.
“Until recently, there hasn’t been a lot of real good burbot research,” he said. “Mostly because nobody’s really interested in catching them.”
Jeff Gillies writes for Great Lakes Echo.

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