Trees and Limbs in Rivers Help Fish Survive Floods | Environment | Seven Days | Vermont's Independent Voice

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Trees and Limbs in Rivers Help Fish Survive Floods

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Published August 9, 2023 at 10:00 a.m.


Left to right: Luke Holland, Jud Kratzer and Levi Brown with electrofishing gear - KATIE FUTTERMAN
  • Katie Futterman
  • Left to right: Luke Holland, Jud Kratzer and Levi Brown with electrofishing gear

Last month's flooding likely walloped Vermont's fish population as the heavy rains turned rivers and streams into torrents. Vermont Fish & Wildlife Department officials don't have estimates of the losses, but some of them think the damage could be comparable to Tropical Storm Irene in 2011, when up to 58 percent of the state's fish were killed or displaced by the flooding.

In particular, trout — rainbow, brown and brook — face threats from the massive flooding. Fish can get "blown out" and washed into unsuitable habitats, according to Will Eldridge, an aquatic habitat biologist for the state. They can even end up out of waterways and perish stranded in fields and ditches when floodwaters recede.

The oil, manure and other waste that gets into the water during flooding can also harm fish. Sediments, especially when moving swiftly during strong storms, can be particularly harmful to their fragile gills, according to Ellen Marsden, a fisheries biologist and professor at the University of Vermont.

That said, she added, "Fish cope with this. This is their life ... And when it starts rushing, they seek refuge, and they know what they're doing."

Those refuges are formed by rocks and wood. They not only protect fish in fast-moving water but create niches where fish can both hide from predators and eat the smaller organisms growing there.

Previously, officials encouraged people to remove debris such as logs from rivers and streams. But a new approach encourages a "messy" waterway, full of fallen limbs and trees.

The Fish & Wildlife Department launched a study in 2012 to evaluate how fallen trees and limbs affect the brook trout population. It added wood to 57 miles of the East Branch of the Nulhegan River in the Northeast Kingdom.

Last month, this reporter accompanied state biologists to the waterway near Averill as they used electrofishing to stun and count the number of brook trout. The group explored an area where trees had been added, as well as a control area that had been left alone.

Wearing waders in thigh-deep water, Jud Kratzer and Levi Brown strapped on battery-powered backpacks and put out hoops, which created electric currents that forced the fish to swim into nets held by Ora Astbury and Luke Holland.

While the Northeast Kingdom was largely spared from last month's historic flooding, the team did have a more difficult time catching fish due to high water levels from recent rain. But that only made for more excitement when it spotted a brook trout. Brown would yell, "There's one! There's one!" and the rest of the team would splash across the water to zap and net the fish.

They caught 17 trout in the treatment site and 13 in the control area. The control site typically experiences some spillover benefits from an increase in trout in the wooded area right next to it, Kratzer said.

KATIE FUTTERMAN
  • Katie Futterman

Bottom line: Adding wood to the water has been a success. The study estimates that there are now 67,000 more brook trout in northeastern Vermont than expected because of the trees, according to Kratzer. Within the first four years of the study, brook trout biomass — the total weight of them all — tripled.

He's confident that had the area flooded, the fish populations would have fared better. The department is planning to study fish post-flooding in other places.

Trees in streams don't just aid the fish population. They also move the water laterally and slow its flow.

Learning from the mistakes of Irene, the state has made a concerted effort to educate the public on the benefits of woody streams. The Agency of Natural Resources runs an education program called Rivers & Roads, in which state biologists train members of the Agency of Transportation on how to do roadwork in a way that's more compatible with functioning streams and rivers.

The Stream Wise program works with private landowners and municipalities around the Lake Champlain basin and educates them on the benefits of wood in water.

Officials in charge of a project on Pinney Hollow Brook in Plymouth are also learning from past mistakes. After Irene, berms were built to keep water in the channel there, which only made the stream more powerful and destructive downstream. The state is now planning to remove the berms and reconnect the flood chute and will also work to restore fish habitat by adding wood.

The department has also removed dams that acted as barriers to fish migration, according to Eldridge. As of the last report, in 2020, 98 dams had been removed. These efforts should provide a faster recovery, as Eldridge expects existing fish to naturally reproduce more easily, while fish from elsewhere will colonize areas they previously could not reach.

The state plays another key role in maintaining Vermont's fish population. Each year, five hatcheries raise hundreds of thousands of fish that are stocked in Vermont's lakes, ponds and streams.

During Irene, the Roxbury Fish Culture Station, which produced 60,000 brook and rainbow trout annually, was destroyed. It took nine years — and $6 million — to reopen it.

It stood strong during the July flooding thanks to improvements, according to Dylan Sickles, the fish culture operations manager. Much of the fish-production area was placed at a higher elevation when the facility was rebuilt. Sickles said improvements to a retaining wall also helped it weather the storm.

The original print version of this article was headlined "Wood Is Good | Trees and limbs in rivers help fish survive floods"

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