Habitat drastically shrinks as climate change, removal of shade trees make streams too warm
By: Ad Crable, BayJournal.com
About 100 days a year, you will find Michael Garrigan by himself with a fly rod, sneaking along small mountain streams hoping to catch and hold, just for a few seconds, a small trout widely revered as the jewel of freshwater fish.
It’s not just the haloed dots, shadings and multi-hued colors of the wild brook trout that enthrall anglers like Garrigan, of Marietta, PA, though that would be reason enough. “They’re wild and they’re native. There’s something innately beautiful about that,” Garrigan said. “There’s a special allure finding water that has brook trout in it. It’s usually the most remote and close to wild you can be in Pennsylvania. There’s that connection to something that is of that place.”
Recognition of wild brook trout — the East Coast’s only native trout — as an important cultural, recreational and economic icon has never been stronger. Scientists and policymakers also point to the brook trout as an indicator of water quality in streams that eventually feed the Chesapeake Bay.
“Saving brook trout is saving the Bay in a big way,” said Alan Heft, a state fisheries biologist, and brook trout program manager for the Maryland Department of Natural Resources.
Brook trout are found along the Appalachian Mountains from Georgia to Maine. They are the state fish of nine Eastern states, including Pennsylvania, New York, Virginia, and West Virginia, all of which are in the Bay watershed.
Yet “brookies” are gone from an estimated 60% of their historical range in the Bay’s drainage, mainly because of human development and competition from the nonnative and more aggressive brown trout and rainbow trout. Incredibly sensitive to pollution and sedimentation, one study found that the brook trout is doomed if even 1.5% of its watershed is covered by impervious surface.
Brook trout also depend on cool water, and their scientific name means “dweller of springs,” indicating their reliance on colder temperatures. Their precarious state has worsened as forest loss and climate change warm the streams where they live. The widespread loss of hemlocks, which shade many headwater streams, to a nonnative pest called the woolly adelgid has also depleted brook trout habitat. The lacy green trees were once so synonymous with the fish that they often were called hemlock brook trout.
In the face of such alarming declines, unprecedented efforts and money are focused on preserving and improving brook trout habitat — mostly small forested streams — and even restoring brookies to streams where they used to swim. Virginia recently resettled brook trout in several streams in the Massanutten Mountains where the fish disappeared generations ago. In Western Maryland, limestone treatments were used to restore brookies to several streams long made fishless by acid mine drainage.
The save-brook-trout movement began in 2006 when conservation groups, universities, and state and federal agencies from 17 states formed the Eastern Brook Trout Joint Venture.
Since then, harmful pollution, such as acid rain, which can make streams too acidic to support trout, has improved considerably.
New technology is aiding the effort, such as the use of computer modeling to predict where streams will warm and help identify where to plant or preserve streamside trees that shade and cool the water. Satellites can help locate where cool underground springs add colder pockets of water to a stream, steering conservation efforts toward them.
Genetic studies have revealed that brook trout live longer than was thought and some will swim far to survive. A study that tracked brook trout in Maryland, for example, found ones that lived up to 8 years and swam more than 6 miles. Another found that some brookies will hang in place, perhaps even as lethal warm water envelopes them, while others are wanderers and will relocate to survive. In the future, managers may zero in on peripatetic trout and use them to establish new populations. Sampling for the presence of brook trout is vastly more efficient with the emergence of environmental DNA or “eDNA.” A laboratory filter that captures the biological material shed by trout is simply placed in a stream and collected later. No need to net or shock trout to see if they are there. Samplings can also reveal important information about trout densities and the health of the population.
But climate change has emerged as a looming new threat that many fear will add the extra few degrees in water temperature that could tip the balance.
“The threat of warming temperatures from climate change is the number one threat. No question about it” said Jason Detar, an area fisheries manager for the Pennsylvania Fish and Boat Commission, which has seen the state’s watersheds holding brook trout shrink by one-third.
“I’m very concerned about that. I think the reality is we’re going to lose brook trout habitat,” added Fred Henson of the New York Department of Environmental Conservation.
In a 2015 report on the impacts of climate change, the U.S. Environmental Protection Agency warned that coldwater fish habitat could decline by as much as 62% over the next 80 years. And the state-federal Chesapeake Bay Program, which has made brook trout a priority, has said the species could become regionally threatened within three or four decades.
The Maryland Chapter of Trout Unlimited said that warming water over the next 100 years could eliminate brook trout from the state, except for one county in western Maryland. In Virginia, the National Wildlife Federation warned that the species could be gone as soon as 2050 from all of its 614 brook trout streams.
The Eastern Brook Trout Joint Venture has tweaked its mission because of climate change. “Our focus now is to assure [that] the brook trout that we do have can move around where they need to go within a system,” stated Stephen G. Perry, the effort’s coordinator.
The danger of climate change is straightforward enough. Unlike the more tolerant rainbow and brown trout, brook trout need water temperature near 68 degrees. Adults can survive water warmed to 77 degrees, which results in less oxygen, but reproduction slows when the temperature hits 70.
Except in higher elevations, many streams where brook trout are found in Bay states are perilously close to that tipping point. Without ideal stream habitat and shading trees overhead, a degree or two could render a waterway section troutless.
“I think there probably will be a shift favoring northernmost brook trout streams in our watershed,” said Jennifer Greiner, a U.S. Fish, and Wildlife Service liaison to the Bay Program.
“It’s vital that we protect the best of our best [steams] right now,” Heft said.
Another threat from climate change is predicted greater rainfall. High water in winter can sweep away eggs and fingerling trout.
While the ultimate fate of brook trout remains uncertain, a formidable coalition of private and public efforts has been pulling out all of the stops to, as one popular license plate puts it: “Back the Brookie.”
“It’s not looking optimistic, but we’re going down fighting,” said Scott Scarfone, coordinator of the Upper Gunpowder Falls Watershed Trout Conservation Partnership, which led a successful effort to establish a brook trout population in the Upper Gunpowder River. The project involves mostly private landowners not far from Baltimore.
It’s one of only three brook trout strongholds left in Maryland. The other two are in Garrett County and in Frederick County near Catoctin Mountain Park.
One of the chief strategies to stave off thermal pollution is planting buffers to shade streams. “Planting trees is an amazingly simple thing to do to get the largest impact in the quickest amount of time for the least amount of dollars,” Perry said.
Another push has come to replace old culverts that are prone to streambed scourings at their ends, cutting off trout from migrating in search of better habitat. Highway departments now use more fish-friendly culverts to replace old ones or when new road crossings are built.
In Pennsylvania, there has been a concerted effort in the last 10 years to find and document all of the streams that hold any kind of wild trout, especially smaller ones. About 16,000 miles have been found so far. Once documented, the best are given protection from development.
Hands-on projects already are underway to give brookies a fighting chance against climate change.
In Big Hunting Creek in Maryland’s Catoctin Mountain Park, wild but introduced brown trout, which muscle out brookies for food and eat their fingerlings, are being caught and transported farther downstream where a waterfall blocks their return. The U.S. Geological Survey hopes to reintroduce sculpin, a small fish that is part of a healthy brook trout stream ecosystem, to several streams in the park.
Unquestionably, the future of brook trout is at a critical juncture. Even more, resources must come to bear to make streams as good as they can be as warmer temperatures move in.
Many of those trying to save the brookie point to the importance of getting the public aboard so that they clamor for all that can be done and that private landowners agree to be good stewards of streams in their midst.
“If the general public places a high value on our streams, then there can be a concerted effort to work collaboratively to conserve these resources,” Detar said. “Otherwise, I believe the handwriting is on the wall for these systems.”
Brook trout in the Bay states
Native wild brook trout have been declining in every state with streams and rivers that drain into the Chesapeake Bay. Here are the status and predictions for a few of the states based on predicted impacts from climate change and development.
- Gone from 62% of their historic range
- Found in 151 streams. Significant populations found in only three parts of Maryland: Garrett County in Western Maryland, Baltimore County in the Upper Gunpowder Falls watershed and Frederick County in Catoctin Mountain Park
- One wildlife group predicted brook trout could disappear from all streams in the state with the exception of some in Western Maryland, by 2100.
- Gone from 35% of their historic range
- Found in 614 streams
- One climate change model predicted the elimination of brook trout from the entire state by 2050.
- Gone from 34% of watersheds
- 39% of watersheds that still hold brook trout have populations half their original size.
- 16,000 miles of streams have wild trout; much of that includes brook trout.
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