Scientists identify it as Salvelinus namaycush. Other names include mackinaw, lake char, touladi, togue, siscowet, and paperbelly. Lots of people call it, simply, a lake trout. It’s a freshwater fish found in many northern lakes in North America.

In Lake Champlain, lake trout spawn at several reefs. Ellen Marsden, UVM professor of fisheries, has found extremely high densities of trout eggs and young fish (called fry) at these spawning sites.

But that’s where the happy story seems to end. Annual assessments of adult lake trout reveal that nearly all them are clipped; that means they were born in state fish hatcheries. There appears to be nearly zero natural reproduction of lake trout in Lake Champlain. That’s worrisome to biologists and fishermen—and expensive too.

Ellen Marsden and her students have been searching for more than a decade trying to figure out why. They’ve gone down in scuba gear and paddled in boats. This year, they got Zippy, a tiny orange submarine (or ROV for remotely operated vehicle) to help them in the search for answers.