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Wildlife Watch: Fish grow on trees

Published: Sep. 28, 2021 at 3:30 PM EDT
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BARNET, Vt. (WCAX) - Have you ever heard the expression “fish grow on trees”? It’s the phrase behind work biologists are doing in Vermont streams.

“Strategic wood addition is the process in which we strategically add large woody material in the form of whole trees to streams in order to improve fish habitat and stream functions,” said Jud Kratzer, a fisheries biologist with Vermont Fish and Wildlife.

Kratzer says that since 2012, the state has completed strategic wood addition projects on more than 40 miles of stream in the Northeast Kingdom.

“There is a lot of thought and planning that goes into this,” he said.

Kratzer says when they evaluate an area for intervention, there are several things they look for.

“We have done two studies in northeastern Vermont relating to this. And the first study we found that the streams that have the most brook trout in them were the streams that had water temps that were cold enough for brook trout and they had a lot of large, woody material in them. They had a lot of trees that had fallen down into the stream. The next study that we did we actually went and added trees into streams and we monitored the brook trout population to see what happened. And it turns out that the brook trout population tripled on average in places that we added large, woody material. So that proved that wood is important on brook trout,” he said.

They are also working to improve the stream itself.

“Large wood material and streams perform several functions. I’ll just highlight a couple of them. We are in the fall now and leaves are falling off the trees and some of those leaves will end up in streams. We want those leaves there. We don’t want them to wash downstream because those leaves decompose and become food for insects, which is then food for the fish. So you need some things like pieces of large wood or large rock that will capture those leaves and keep them in the stream rather than washing them down the stream,” Kratzer said.

And also help create flood resiliency.

“By having things like large wood and boulders in streams, especially the ones that are higher up on the mountains. We think of those as roughness in the channel. They tend to slow the flow down, so when you get big rain events, you are slowing the flow up high, up in the hills and mountains rather than that water just rushing downstream to the valleys where everyone lives and increasing the risk of flooding,” Kratzer said.

As well as changing the culture around wood and streams.

“We start to think as rivers, not having wood in them. When in reality they should have wood there. We are adding wood to streams to show that wood can stay there, it can be safe, it can be secure and it can perform important functions for fish and stream function,” Kratzer said.

When workers add wood to the water, they keep you in mind, too.

“We are only doing this work in places where we are not going to be impeding boating and swimming and that sort of thing. We are usually working in smaller streams that are higher up in the watershed,” Kratzer said.

All to help the ecosystem and conserve the land.

“Ultimately, what we want to have is a natural system with trees that are naturally falling into the stream and restoring natural functions into our streams,” Kratzer said.

Reporter Ike Bendavid: It’s like fish grow on trees?

Jud Kratzer: That’s right. Fish grow on trees. That’s what we like to say to make that point.

Click here for more information on strategic wood additions to rivers and streams.

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