Brook trout navigating uncertain waters

March McCubrey has been fishing for brook trout in the White Mountains of New Hampshire since he was a child.

“Some of my earliest memories are my dad taking me out, hiking into backcountry beaver ponds and slogging through the brush to get out to these tiny little streams that fed into them,” said McCubrey, chairman of the youth education committee for Trout Unlimited. “It’s a long standing family tradition, and it’s something that my boys are very passionate [about].”

But the cherished pastime of McCubrey and other anglers across New Hampshire is in peril, as local brooks and streams warm due to climate change, threatening the brook trout.

Brook trout, which inhabit rivers, lakes, and narrow brooks, need cold water. Scientists predict that in New Hampshire during the decades ahead general air temperatures will increase, warm seasons will lengthen, and droughts will become more frequent. These effects, in addition to other factors like warm water runoff, jeopardize the brook trout, which can only withstand water temperatures up to 67 degrees. Any warmer, and the fish has to move—or die. Some anglers say that many areas in southern New Hampshire where brook trout once existed decades ago are already devoid of the fish.

“If all the brook trout died in the state, there would be thousands of miles of stream with no fish for people to catch,” said John Magee, habitat biologist of the New Hampshire Fish and Game Department’s Inland Fisheries division.

The brook trout would also be a sore loss for scientists, as the species is often an indicator of the health of a freshwater habitat. Brook trout can’t survive in areas where water quality is poor—whether that means high temperatures, low oxygen levels, or problems with acidity levels. Scientists can use the presence of the fish as an indicator of the stream’s health.

“When they’re not present, it’s a matter of, ‘Okay … what’s the problem?’” said Dianne Timmins, a coldwater fisheries biologist from New Hampshire Fish and Game.

As water temperatures increase and become less oxygenated—one result of warming water—brook trout are forced to leave. But other species could soon follow, also hurt by the changes in water quality. Stoneflies, important to the diets of some fish, need highly oxygenated water to survive. Amphibians, such as the spring salamander and the mink frog, also need cold water, and could follow the brook trout out of the ecosystem. Eventually, the whole food chain suffers, with animals like kingfishers, otters, and minks lacking food.

“If you find [brook trout] in a stream, then that stream is doing pretty well in terms of health,” said Magee.

Because ecosystem changes that affect brook trout also ripple to other creatures in freshwater habitats, researchers have chosen to focus some conservation efforts on protecting the brook trout from the climate change effects that might already be underway.

“The idea was to figure out which fish species was really in danger, and then focus our effort on those species. That doesn’t mean we aren’t trying to save all species,” said Magee. “Everything we do is also going to help those more native species, that are a lot more common.”

Scientists must closely track the brook trout’s life cycle, and therefore its basic needs, in order to understand how they can help it withstand climate change effects. Fish and Game researchers have been implanting radio trackers into brook trout for the past few years to learn where they travel.

Female trout lay their eggs around late September, beating their tails on the ground to create a nest where oxygen can flow. Four to six months later, those eggs hatch. For a few months after hatching, the brook trout will linger in the same area and feast on small crustaceans and aquatic insects. A warm, rainy April could bring floodwaters too strong for the young fish to withstand, cutting some of their lives short. Brook trout will only be a couple inches long by the summer after they hatch—but they must seek refuge in colder waters, such as deep pools or tributaries.

The little fish can travel dozens of miles through mazes of streams in New Hampshire in search of protection from the heat, especially in areas like the Dead Diamond and Ammonoosuc watersheds, where a vast network of waterways is interconnected.

But average annual maximum temperatures in New Hampshire have increased between 0.5 to 2.5 degrees since 1970, according to a climate impact assessment published by the UNH Sustainability Institute. The assessment predicts that average temperatures will increase 3 to 5 degrees by 2050. Longer and hotter summers, caused by these temperature increases, would force trout to travel farther and stay longer in their cold shelters. Droughts caused by global warming could dry up some of those narrow refuges, restricting habitat further, according to researchers from Trout Unlimited and Fish and Game.

When brook trout spawn, they often return to some of the same areas—no matter how far that may take them. Magee recalls a case where a radio-tracked fish traveled 75 miles in a year. But culverts and dams that fragment brook trout habitats can cut off these routes and exacerbate the looming climate change threat. Though researchers understand most of the brook trout’s life cycle, they still hope to learn more. It still isn’t certain why brook trout prefer some places more than others for spawning.

A glimpse of what New Hampshire streams may look like in a warmer climate already exists 450 miles south, in the Chesapeake Bay Watershed. The US Geological Survey has tracked water temperatures in that area since 1960. Almost 50 stream sites out of 129 measured in Virginia, Maryland, and Pennsylvania warmed 2 degrees or more, according to EPA analysis of the USGS data. The increase is likely a result of several factors — including longer-term climate change, but also increased runoff with human development, according to the EPA.

The species has been nearly eliminated from the Chesapeake Bay Watershed, though they were once abundant inhabitants of the area, according to data from the Eastern Brook Trout Joint Venture, a partnership of various organizations working to conserve eastern brook trout. The Venture also maps brook trout inhabited areas throughout New Hampshire. There are pockets in the lower half of the state where the species no longer exists, though anecdotal evidence from decades ago suggests brook trout once lived there. It is difficult to measure fish populations even with today’s technology, so the exact time frame and quantity of the loss is unknown.

Temperatures in New Hampshire brooks and streams have only been tracked for roughly the past decade, so researchers also don’t have a record of data to determine how much the streams have warmed over a longer period. Magee said that “hindsight is 20/20,” and that local scientists just weren’t focused on measuring long-term stream temperature back in the 1960s, when it would have been useful.

“When did people start doing that? They started doing it when it became apparent that they should do it,” Magee said.

One extensive study is being conducted at Dartmouth college, where researchers have been tracking stream temperatures relative to air temperature in Northern New Hampshire for over a decade. By understanding the relationship between the two, they hope to model prospects for the brook trout as air temperature continues to increase.

Scientists at organizations such as Trout Unlimited, a group dedicated to conserving, protecting, and restoring coldwater fisheries throughout the US, have teamed up with NH Fish and Game to perform other research and restoration that enhances habitat around the tributaries and rivers needed by the brook trout. The two organizations are performing ongoing restoration of riparian zones, the vegetation along the banks of rivers. Thick growth in that area shelters the water from the sun and keeps it cool.

Current work by these partnered researchers even involves strategically placing wood into areas of the river, creating vital pools of deeper water for brook trout to use.

And New Hampshire’s Trout Unlimited chapters have been regularly campaigning along with NH Fish and Game to remove dams and replace culverts across the state for over a decade. Paid TU staff in Concord are trained to find culverts that could inhibit passage of species like the brook trout and form proposals for a town’s conservation committee arguing for the replacement of the culvert.

Actions like this could also be helpful for humans, as they reduce flood risk by allowing swelling waters to pass through unhindered, according to McCubrey. He calls culvert replacement “one of those win-win situations.” Climate assessments project that New Hampshire will get more sudden flooding as global warming increases.

Magee estimates that 15 to 20 dams have been removed thanks to efforts across the state, but the number of replaced culverts could be well into the hundreds, particularly after NHDES permit rules changed, requiring all replaced culverts to allow passage for aquatic species.

Projects like culvert removals see benefits immediately, as dozens of fish are able to pass through on the day the culvert is replaced. But the other conservation projects will have more long-term benefits.

“There are land conservation projects we’re doing now, where it might take three years to conserve some property,” Magee said. “The real value is 50 or 100 or 200 years from now in making sure the habitats … are conserved.”

Those who will benefit most from conservation work will be future anglers and future brook trout populations, as these new refuges help to slowly rebuild trout numbers and protect against future impacts.

McCubrey, as well as other researchers and activists, said they are confident that the diverse work now being performed by TU and Fish and Game will have an impact.

“I feel hopeful. Maine and New Hampshire, we’re going to be some of the last holdouts for the brook trout as the climate warms up,” McCubrey said. “If all the predictions are true and it can’t be stopped, I think what we’re doing is the best thing we can possibly do, to protect what we have in the best possible way.”

For McCubrey, a large part of being an angler himself is also being involved in activism.

“I come out of a very strong tradition of being a sportsman conservationist. I interact with the natural world with a sportsman’s eye. For me, it’s a kind of a no brainer, if you will,” he said.

If brook trout habitats are greatly reduced, New Hampshire could theoretically stock all the vacant rivers with non-native species, such as rainbow and brown trout, to keep the local sport fishing industry alive. New Hampshire Fish and Game is one of the few organizations currently responsible for stocking fish in areas where brook trout are not too prominent, such as the Seacoast. However, Timmins said these programs will not be easy to expand if the need arises. Stocked fish are largely unable to reproduce in local streams once they are released, so fisheries would have to be stocked in perpetuity to maintain sport fishing, which she says is not a financially sustainable option.

“The absolute most expensive part of our [Fish and Game’s] fishery budget is our hatcheries,” Timmins said.

She estimated that it has cost between $13 and $16 per pound of fish for food, salaries, stocking trucks, and other hatchery operations.

“A lot of people don’t see that side of it, but that’s the reality,” she said.

And some anglers, like Paul Doscher, secretary of the national leadership council of Trout Unlimited,  appreciate fishing for a native species like brook trout in remote areas.

“Fishing for wild fish is honest. … It’s about something that’s real,” Doscher said. “It’s not an artificially created fishery, created solely for recreational purposes. It’s a way to connect with nature and with a species that is iconic.”

(Brook trout photo by David Van Wie.)

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