Let’s Talk Fish: UVM’s Ellen Marsden

By Kenrick Vezina

You’ve got a 15-foot, 800-pound sturgeon on your hands – and it’s ornery. This massive, bony-plated fortress of a fish is misbehaving. What should you do?

“Stick your thumb in its mouth,” says Ellen Marsden confidently, explaining that the surest way to soothe sturgeon is by allowing it to suckle.

Such gems of fisherwoman wisdom pop up regularly in conversation with Marsden, 51, a professor of conservation biology and ichthyology at the University of Vermont (UVM).

Marsden started her life in northern England, lending an exotic (by Vermont standards) British accent to her lectures. She moved to the U.S. as a young teenager and has lived in Vermont since 1996. She currently resides in Burlington.

As we head to her office, she declares exuberantly, “Let’s talk fish!” and favors me with the look of a child who has just been asked to list her favorite dinosaurs.

Marsden is as affable a scientist as you could hope to meet. Her lecturing style is loose and conversational. Her demeanor is warm, and she’s not above taking a moment during complicated population modeling exercises in a crowded computer lab to discuss the film Master and Commander with one of her students – or go contra dancing with them after class. The ease with which she conducts herself belies an impressive mastery of all things fishy.

Marsden has had a hand in several different organizations. Prior to landing at UVM, she worked for the Illinois Natural History Survey as director of their Lake Michigan Biological Station. Currently, she works with the Great Lakes Fisheries Commission “a lot,” and with a number of state and federal agencies, though, she adds, “only UVM pays my salary.”

But how does one end up as a professor of ichthyology? It’s not the most commonplace specialty, even among biology students.

Her interest in fish stems, as one might expect, from a formative childhood experience. Marsden was lucky enough to have a pond form accidentally near her home due to human activity. Her face suffused with nostalgia, she recalls spending “days; hours [at a time]” watching the ditch full of water and mosquito larvae develop into a thriving aquatic ecosystem rife with frogs and fish.

Still, Marsden wasn’t thinking of fish when she later decided to become a veterinarian. Fish seemed like little to no fun as study subjects: they were “slimy, cold, and live in water.”

But while working on frog genetics, a fisheries biologist who needed help with his project offered to take Marsden on as a mentee. She had the technical skills required, but she hesitated. Would scuba diving be part of the work? Her soon-to-be-mentor stated flatly that “fisheries biologists don’t scuba dive” – but he was willing to entertain the then-unorthodox idea if Marsden would join his project.

Turns out, Marsden was ahead of the curve. The Cousteau era of underwater biology and documentation soon led to a paradigm shift in the way biologists study aquatic species. Two years after Marsden became certified as a scuba diver, her mentor did, too. One thing led to another, and so it was that Marsden quickly found herself a scuba-diving savior of scaly, submerged organisms.

Lately, she’s been focused on the lake whitefish. This silvery, foot-and-a-half-long fish is a fan of the deep, cool parts of freshwater lakes. It’s also tasty – as “prized as a Friday night fish fry,” according to Marsden. But being delicious is not a good omen for a fish. Whitefish, once common in Lake Champlain and the Great Lakes, were overexploited by commercial harvest throughout the 19th century.

Harvesting finally stopped in 1914 on the U.S. side of Lake Champlain, though it continued for a time in the Canadian portion. Then something interesting happened. Despite being a hugely popular commercial species, whitefish basically fell under the “sonar” while attention was paid to other lake conservation efforts –eliminating sea lamprey, restoring lake trout, dealing with zebra mussels and other invasive species.

As a result, when evidence arose that whitefish populations were suffering a new collapse, Marsden realized that “nobody’s been watching out [for whitefish] since a study in 1930.”

That’s a nearly 40-year data deficit for Marsden to tackle. If she’s intimidated, she shows no outward sign. Rather, she brims with excitement. Asked to talk about her time in the field – she refers to this work as “playing” – she rubs her hands together like an excited child. “Ooh!” she exclaims.

When Marsden began her current project, she was faced with a tricky problem: she didn’t know where to find the fish. To study a species, you have to find it first. And when a species was once hauled up in nets by the ton, its absence is rather striking.

So Marsden spends entire days motoring around Lake Champlain looking for whitefish, basing her search on woefully out-of-date data. Nowadays, she is lucky to encounter even a single adult whitefish in her nets before the end of the day.

Though the larvae aren’t much more in evidence, they appear to be the best means by which to find whitefish. Using finely-meshed nets, Marsden and her cohorts strain the water in likely areas, collecting containers of lakewater and a suite of multifarious, minute creatures that must be sorted through later to sift out the whitefish. It’s not unlike looking for tiny, living needles in a wet haystack full of other, tiny, living needles.

Still, Marsden’s efforts to get to the bottom of why the whitefish are vanishing from Lake Champlain are not likely to consume her time forever. Some scientists pick a particular species and spend an entire career focused on it; Marsden is not one of these. She has, even in her recent career, covered a wide swath of aquatic species.

Her research has supported efforts to control the sea lamprey in Champlain – a parasitic species which preys on several popular sport fishes, with a special penchant for wounding lake trout.

Sea lamprey look like slimy, sickly green socks with teeth; Marsden thinks they’re “cute.”

She has also worked on invasive, exotic mussel species, like the well-publicized zebra mussel. Exotic mussels are out-competing North America’s native species at a staggering rate, and mussel life cycles are often directly linked to those of fish via a parasitic life stage.

She is, in short, a busy woman.

Despite her wide-ranging interests in the aquatic world, even the tiniest water creature inspires her affection. The scruffy little sculpin, a miniscule bottom-dweller, has broad pectoral fins that look to Marsden not unlike wings from some Da Vinci flying machine. When a scuba-diving biologist such as herself happens upon them, they do little “push-ups” on the lake floor in an attempt to frighten away the intruder.

And one piscine predator is paramount in her heart: the lake trout. Marsden sings the praises of this “noble beast” with abandon. She has worked with lake trout in some capacity for almost twenty years. Currently, they are part of a massive, Great Lakes-wide restoration project.

She happily rattles off the reasons for her special regard. “We owe it something,” she declares, given humans’ overexploitation and extirpation of the species in Lake Champlain. It’s a top predator, the lake equivalent of a mountain lion. It’s long-lived, capable of surviving 50 years or more.

Most of all, it’s an ecological indicator. As she puts it, “Clean lake trout equals clean lake.”

At the end of the day, that’s really what Marsden is pulling for. Countless people – anglers, swimmers, boaters, tourists – depend on Lake Champlain for livelihood, entertainment, and recreation. Without a healthy ecosystem at the base, no one will get what they want or need from the lake. It’s Vermont’s special, not-quite-great lake, and conservation biologists like Ellen Marsden are doing their best to protect and preserve.

A 2009 UVM grad, Kenrick Vezina is a newly-minted freelancer with lofty science writing aspirations, who enjoys both animals and alliteration.