Invasive sea lampreys in Great Lakes, and the lake trout they prey on, puzzle scientists

[marmar]

(Detroit Free Press) It's a mystery.

Invasive sea lamprey, the Great Lakes' biggest predator, primarily feed on lake trout, one of the lakes' most prized sports fish. When trout populations are high, researchers expect to see fewer lamprey-wounded fish, and more of those wounds when lamprey populations are spiking.

But that's not always what scientists are finding.

New research into what may be behind the discrepancies holds promise to improve how sea lampreys are controlled in the Great Lakes, protecting a $7 billion fishery. It could allow lamprey managers to examine whether they have switched to other fish species as food sources, or whether lamprey and trout numbers in particular regions of Great Lakes should be more closely reviewed — helping direct their limited resources to hold back the invaders.

"When we saw the lake trout population go up, we would expect to see the wounding rate go down, or, if we saw the sea lamprey numbers go up, we would expect the wounding rate to go up. And we did, for the most part, see those things on a year-to-year basis," said Jean V. Adams, a biology statistician with the U.S. Geological Survey based in Wisconsin. .........(more)

https://www.freep.com/story/news/local/michigan/2020/09/25/invasive-sea-lampreys-trout-great-lakes/3523358001/