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Lake Trout and the Tao of Research

Trout and light. Graphic by Chris J. Benson, Minnesota Sea Grant

Trout and light in Lake Superior.

Garrison Keillor recently said on Prairie Home Companion, "This is the thing you learn when you are with scientists: they have much more fun than any of the rest of us." Keillor made that statement after joining University of Minnesota Duluth (UMD) researchers aboard the R/V Blue Heron to collect water samples from Lake Superior. Trevor Keyler wasn't among them. Keyler, a Sea Grant graduate student at UMD, was polishing his Master's thesis, which he reports was worthwhile but not "fun" in the traditional sense of the word.

"Fortunately I like writing and I'm not afraid of odd hours and hard work," said Keyler, citing some of the "beyond-collecting-data" fundamentals of scientific pursuits. Under the guidance of Al Mensinger and Tom Hrabik, both professors in UMD's Department of Biology, Keyler spent the last two years studying Siscowet lake trout, a species of fish that lives in the deep dark waters of Lake Superior. For many of the hours during those years, he was cold, wet or watching fish do very little. Such is the way of aquatic science.

Trevor Keyler, Graduate Student at UMD

Trevor Keyler, Graduate Student at UMD

Keyler's thesis details how Siscowets become increasingly better at catching prey as complete darkness moves toward the equivalent of the dim light shed by a quarter-moon (after that additional light doesn't improve either the prey's or the predator's odds). What Keyler's thesis doesn't record is the year-and-a-half he spent building a foraging arena in Hrabik's laboratory to house his study subjects. "I took a lot of trips to Home Depot," said Keyler, who earned his degree in November. "Building the arena was extremely frustrating. There was no model to follow and we made a lot of design changes. Solving the lighting problem alone took over a month."

The lighting problem shone from the infrared bulbs, not the blue-green lights mimicking the dim glow at 100 meters deep. The infrared lights were needed to record siscowet foraging in the dark but simultaneously created a blinding glare on the water's surface making recording fish movements impossible. The researchers overcame this conundrum with custom-made acrylic inserts to deflect the glare.

Hrabik said, "One of the fun parts for me was witnessing Trevor's creativeness in experimental design and problem solving." In part due to the careful construction of their housing and arena, none of the Siscowets died during the research; they were still feisty as of November 2014. Other examples of successful adult Siscowet husbandry are unknown or unreported and the techniques that Keyler, Hrabik and Mensinger developed may aid the care of other freshwater fish. Keyler even took
precautions to protect the fish from retinal damage when they were brought to the
surface near the Apostle Islands. This is recorded in Keyler's thesis.

What also goes unrecorded in the thesis is Keyler's enthusiasm for Popcorn, Tweedy, Barney Barnwell, and the other fish he cared for and cheered for. Like the Moonshiners of Discovery Channel fame for which they were named, these fish knew how to work in the dark and Keyler was right there with them, or nearby watching a six-camera feed.

Pelagic salmonids like Siscowet are 'round-the-clock, predominantly visual feeders. While some ocean fish seem to detect light as deep as 1000 meters, the abundant suspended particles in fresh water typically render sight useless below 100 meters. Siscowet are unique freshwater beasts because, among other things, they can see their next meal in the light-limited pelagic zone of Lake Superior, at least to an estimated 150 meters.

Recent data suggests Siscowets are near carrying capacity in Lake Superior, gobbling up 80 percent of the Kiyi population annually and over-consuming Deepwater Sculpin. This hunger of theirs may put another kink in the history of Lake Superior's food web, which has plenty of kinks in it already due to a century that has included overfishing and catch limits, Sea Lamprey invasion and control, and the rise and fall of the Rainbow Smelt population.

Siscowet and most of the other organisms in Superior's pelagic zone are relicts from the Pleistocene's arctic seas. The simplicity of this ancient food web makes it ideal for studying food web dynamics and predator-prey relationships.

Some of the results of Keyler's research will inform a foraging model Hrabik and his colleagues have been creating to analyze population trends and make projections to support fisheries management decisions around the lake. Some will factor into Keyler's upcoming research as he stays on at UMD to work toward a Ph.D. studying foraging of additional Lake Superior fish, including walleye. Some of the results, like Keyler's new construction skills, are simply part of the way of science.

Keyler said one of the best moments was creating the first graph based on his data and seeing the trend. Both Keyler and Hrabik, who earned a Ph.D. in Oceanography and Limnology at the University of Wisconsin Madison, agree that science is fun, but, more than that, it is a philosophy. "Doctor of Philosophy, that's what 'Ph.D.' stands for, and that is how I think about my career," said Hrabik. "The philosophy of science establishes a systematic method for addressing questions. The fun part is having the freedom to use the method to discover things about the world around us."

"Answering what might seem like esoteric questions can wind up becoming integral to developing a new understanding," said Hrabik. That's philosophy and that's science and, yes, Garrison, that's fun.

Expect Keyler's thesis, Foraging Mechanisms of Siscowet Lake Trout (Salvelinus namaycush siscowet) on Pelagic Prey, to become a journal article, in the meantime, see related journal articles here.

By Sharon Moen
December 2014

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