TRAVERSE CITY, Mich. (AP) -- A scientific paper released Thursday says the bait fish trade represents a serious threat for spreading invasive species in the Great Lakes area.

Researchers say they tested water samples from tanks containing small fish for sale as bait at more than 500 shops around the eight-state region.

Twenty-seven of the samples tested positive for DNA of invasive fish. Three of the positive hits along Lake Erie in Ohio were for Asian carp, which authorities are trying to keep out of the Great Lakes.

Andrew Mahon of Central Michigan University says the findings suggest that at least some invaders are being spread by anglers who dump unused bait into the water.

Notre Dame scientist Chris Jerde says more consistent bait fish regulation among the states is needed.