Survival of large lake trout as good as the small ones in Lake Michigan

[Hamilton Reef]

Survival of large lake trout as good as the small ones in Lake Michigan

Ann Arbor, MI — Great Lakes' lake trout populations are being enhanced through stocking of hatchery-reared fish to rebuild populations and develop self-reproducing stocks. In Lake Michigan over 2 million lake trout have been stocked annually for decades by the U.S. Fish and Wildlife Service for this restoration effort. These fish enter the lake as yearlings (about 14 months old) and were previously stocked at size of 44 fish/kg. It was thought that raising and stocking larger fish (about 24 fish/kg) would increase the post release survival of these fish in the lake, which would require fewer fish to be raised and reduce crowding at the national fish hatcheries.

Fishery biologists from the U.S. Fish and Wildlife Service and the Wisconsin Department of Natural Resources teamed up to test whether survival of the larger lake trout was greater than the smaller fish. Paired stockings of uniquely tagged small and large lake trout were released in Lake Michigan and recovered over many years to determine relative survival. Recapture rates indicated that relative survival of the two groups was similar, and that stocking larger fish did not benefit the restoration program.

"Apparently the size difference we tested did not benefit survivorship of lake trout, and their overall health condition at stocking is likely more important than size," according to U.S. Fish and Wildlife Service Biologist Charles Bronte.

http://www.iaglr.org/jglr/release/32/32_2_386-394.php

[Hamilton Reef]

NOTE:
"We just published a paper on how offshore stocking (in deeper water beyond the adult lake trout) has really helped the survival of your lake trout. But if the adults are going deeper looking for food, we may have to rethink it," Johnson said.

Lake fish targeted as salmon decline

ALPENA -- It used to be that when Jim Johnson and other biologists went out on their research boats to survey lake trout each spring, they set the nets in about 90 feet of water. That's about as deep as adult fish would go, whereas juvenile lake trout lived deeper, where their parents couldn't eat them.

But four years ago, lake trout were nearly absent in 90 feet, and it was DNR statistical biologist Ji Xiang He who urged his colleagues, "If they're not where you think they are, go look where you think they aren't."

http://www.freep.com/apps/pbcs.dll/a...606290385/1058

[salmon_slayer06]

I heard a rumor that the reason the DNR are planting so many lakers is that the pollution in the great lakes is affecting the lakers reproduction process. When lake trout are fingerlings they spend a certain amount of time on the surface of the lake to breath in air. If they don't do this they die. The lakers are making it that far then they die right after. I was told the top layers of the great lakes are very acidic because of the pollution thats in the air from freighters and and big power plants. The lake trout can't survive in that top layer of water and they don't develop like they should and they all die when they are young. Once the lakers are raised by the DNR, thery are passed that stage and they live in our waters just fine.

Once the DNR stop planting lakers, the population will fall and will not get better. Being the lakers are Native to our lakes, the DNR will rather plant lakers than salmon... and the lakers they will keep on planting.