Rep. David Deen knows the Vermont Legislature, under the unblinking eye of the press and public, can feel like a fishbowl. So when he goes home, the Westminster Democrat escapes with a rod and reel to a secluded open stream.

"Some people use the 'om' sound to get into a meditative state, but flowing water is my mantra," he says. "I totally relax. I focus on what's around me. Birds and wildlife and plants ... You just see amazing things."

Recently, however, he's disturbed by what's disappearing.

Outside the Statehouse, Deen juggles jobs as a private fly-fishing guide and a steward for the nonprofit Connecticut River Watershed Council. Over the years he has welcomed the spring start of trout fishing season by watching streams grow calm, clear and plentiful with potential catch. But in the past decade, fluctuating weather has meant fluctuating levels of water and aquatic life.

Sitting in his chairman's seat in the House Fish, Wildlife and Water Resource Committee room, Deen points to a brook trout mounted on the wall. Dark skinned and light finned, the species is the state's most widely distributed and only native stream-dwelling trout. It requires the high levels of oxygen found only in clear water measuring 50 to 65 degrees.

Vermont's cold, clean rivers and streams offer some of the best wild brook trout conditions in the eastern United States. But as the state's average temperatures are increasing, its cold-water fish habitat is decreasing.

While nearly 14 percent of Vermont's watershed is deemed healthy for brook trout, another 63 percent has degraded because of warmer temperatures and other changing conditions, according to a first-ever study by the Eastern Brook Trout Joint Venture, made up of 17 state fish and wildlife agencies, five federal environmental offices and several conservation groups and schools.

The state's average temperature, which increased 0.4 of a degree over the last century, is projected to rise from 2 to 10 degrees by the year 2100, according to the New England Climate Coalition set up by the region's governors. A report by the U.S. Environmental Protection Agency says a 5-degree rise in average temperature could devastate trout and salmon populations nationwide and eliminate brook trout entirely in Vermont.

"If you're not a fisherman, the fact that brook trout are retreating may not mean much, but brook trout are a canary in a coal mine," Deen says. "They're an indicator species in terms of the health and consistency of the habitat. If brook trout disappear, other things are going to start happening."

End of the line?

To understand why Deen is hooked on brook trout, you need to cast back to his childhood.

The 62-year-old has fished almost since his birth in Abington, Pa., in 1944. He'd pull a worm from the ground, tie it to a cheap line and toss it in the stream near his grandfather's orchard or the pond at his uncle's dairy farm.

"I fished right up until I discovered girls. Then I got married and went back to fishing."

By 1965 he was an organic-chemistry student at the University of Connecticut and a father of two young children. One day, worrying about how he was going to feed his family, he came upon a pond.

"There were big fish in that small pond. We'd have bass once a week."

Then came 1968. Deen, organizing a memorial event after the assassination of Martin Luther King Jr., dropped out of college just short of a degree to become a community organizer. Moving to Westminster in 1972, he headed the Southeastern Vermont Community Action office for low-income people, then won election to the state Senate in 1986 and, after a close defeat for re-election, joined the House in 1990.

All the while he kept fishing, trading the worms of his childhood for fine filament he knots with a surgeon's precision to resemble flies.

"Fly fishing is understanding the entomology of a naturally occurring aquatic organism and being able to imitate it by tying a fly to entice a fish onto the end of your line," he says today.

Deen can loop a simple piece of string into imitations of everything from a newborn water nymph to an adult winged insect to a fly that has laid its eggs and died. He dangles each into the water to see what bites.

It sounds complicated. But Deen has always seen it as an easy channel to the natural world, a chance to let everything else wash away.

Brook trout, for their part, have enjoyed a renaissance in Vermont. Abundant during the state's settlement in the 1700s, the species declined in numbers when loggers and mill workers dumped sawdust and sewerage into rivers and streams in the 1800s. After ecological awareness led to cleanup efforts, a 1962 statewide survey reported an upturn, noting "significant numbers of brook trout" and "a striking amount of natural reproduction."

Then the climate started changing.

Food-chain reaction

Deen noticed the shift a decade ago, just after he earned a master's degree in environmental science from Antioch New England Graduate School in 1996 and became a steward for the Connecticut River Watershed Council, a group based in Greenfield, Mass., that works to protect the watershed "from source to sea," in 1998.

He remembers how Vermont waterways, swelling each spring with winter melt, used to settle down the same time in April, allowing the first mayflies — insects that live in the water but mate in the air — to hatch.

"You can't rely on that anymore. It can be earlier, it can be later, it can happen on time, but it just doesn't happen the way it did when I started fly fishing. The water conditions sometimes are so poor that the insects never actually hatch out. They just hunker down and get swept up by the river."

That ripples throughout the rest of the food chain. Deen used to advertise his Strictly Trout Flyfishing Guide Service with the traditional mid-April start of Vermont's angling season. But since he no longer can predict early spring weather and water levels, "I now tell people I'm not opening my business until the middle of May."

Even so, Deen is seeing fewer brook trout and mayflies. The reason: such cold-water fish and insects require highly oxygenated water found only in cooler streams.

"Over the last 30 years, there has been a steady increase in the average temperature of the Connecticut River. As water temperatures continue to increase, oxygen levels will continue to decline."

Vermont's rivers and streams are warming for several reasons, experts say. When people build houses on the banks, they often uproot trees that shade the water. Dams create stagnant pools that soak up the sun. The Vermont Yankee nuclear power plant in Vernon discharges warm water as a byproduct into the Connecticut River. And, increasingly, global warming is adding to the heat.

The national nonprofit Natural Resources Defense Council and Defenders of Wildlife spotlighted the problem in a 2002 report "Effects of Global Warming on Trout and Salmon in U.S. Streams." Using weather projections from the United Nations' Intergovernmental Panel on Climate Change, they estimated that upward of 40 percent or more of rivers and streams now suitable for cold-water fish will become too warm to sustain them by 2090.

Federal projections are even worse. A New England Regional Climate Variability and Change Assessment done for the U.S. Global Change Research Program says if the Earth's greenhouse-gas levels double because of fossil-fuel burning and other emissions, "the region faces a 50- to 100-percent potential loss of habitat for brown, brook, and rainbow trout."

'Extremes spell trouble'

Deen doesn't need to read scientific reports to grasp the threat. He just slips on his waders and steps outside to see the repercussions of the increasingly changing climate.

Consider when a freak storm causes flooding.

"If you get high water at the wrong time, you wash out all the nests where eggs are laid and you lose an age class of fish."

A drought, in turn, diminishes a stream, which he says decreases the size of fish.

"You need larger waters to grow larger brook trout."

If water levels are too low after fall spawning of brook and brown trout, rivers can freeze to the bottom in the winter, killing the eggs that require a flow of oxygenated water. Similarly, not enough water can endanger spring spawning of rainbow trout.

"Either way the extremes spell trouble for us. Species are attuned to their environment. If the environment changes slowly over a long period of time — a 1,000- or 10,000-year timeframe — most species can adapt. But right now we're talking 50 to 100 years in terms of what we're looking at for weather change. That's short term in ecological time. Species are not going to get an opportunity to adapt."

As cold-water fish wane, warm-water varieties are moving in. Bass, for example, don't need as much oxygen and thus thrive with rising temperatures. Bass are a native species west of the Green Mountains but not to the east. Even so, they're multiplying throughout the state.

"You're going to see a change in the fishery, and that shift concerns me," Deen says. "A lot of people like me prefer wild fish as opposed to fish that are stocked. We'll catch anything, but to know that a fish is wild gives it more panache. There are some brook trout that are stocked, but in our moderate to small headwater streams, that's a wild fish. I worry about losing that habitat."

Retreating upstream

After hooking a brook trout, Deen used to throw it into a hot pan. Now he tosses it back into a cold stream.

"As a fishing guide, they're my inventory. They're too valuable to catch just once. With a good fish of size, you want to keep those genes in the pool and make sure it gets an opportunity to spawn."

A growing group of state and federal agencies agree. The Vermont Fish and Wildlife Department and its counterparts in 16 other states have formed the Eastern Brook Trout Joint Venture. Joining with partners including the U.S. Fish and Wildlife Service and the Trout Unlimited conservation group, the venture is reviewing a draft "conservation strategy" for release sometime this spring.

"People value brook trout not only for their beauty, their delicious taste, and their sportfish qualities, but also as indicators of the broader health of the watersheds where they live," a venture flyer says. "Strong wild brook trout populations demonstrate that a stream or river ecosystem is healthy and that water quality is excellent. A decline in brook trout populations can serve as an early warning that the health of an entire system is at risk."

Deen says the fish already are retreating upstream. He worries what will happen if, according to a recent study by the Union of Concerned Scientists, the state's average temperatures increase enough by the end of the century to make Vermont feel more like the Pennsylvania of his childhood.

"Global warming at predicted levels will have a major impact — in 50 years you're going to have to get into the headwater streams in the ski hills above 1,500 feet to catch a brook trout in the state."

Vermonters concerned about climate change most often worry about less snow for skiing and fewer maples for syrup and sightseeing. But Deen points back to that "canary in a coal mine."

"What else might be changing around us? People who are concerned about maples really ought to be concerned about brook trout. They've been here since the glaciers left. I'm concerned we will lose them."