Support your local beavers!

Well, yeah, take beavers and put them on a different continent, and there are problems. Gee, who'd a thunk it?

Beaver ponds are great nurseries for juvenile fish, especially coho. This includes habitat such as the Puget lowlands. Beaver dams encourage aquifer recharge which helps maintain stream flows during dry periods. They attenuate flooding during big precipitation events by creating flood storage and flood desynchronization. This reduces scour and bedload mobilization. Remember that salmon and beavers evolved together as part of the same ecosystem. Most of the issues with beaver dams are the result of them being in places that are inconvenient for infrastructure. Do they sometimes block fish passage? Yes, but in these limited cases, it's temporary, and it is very rare to find a beaver dam that blocks fish at all flows at all times, year after year after year.

In dry areas, like east of the Cascades, beaver dams raise the water table and encourage growth of riparian vegetation. This is also good for fish, because it means more productive habitat.

Gene S said:

They sure can be. Unless controlled naturally or otherwise the buck tooth wonders can damage fragile ecosystems in short order. We've eliminated a dozen so far within a half mile stretch on a small creek, and there are still more to deal with. PNW streams can be very different from many streams in MT.

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No offense intended but I'm curious about your small creek habitat and if the beavers are native to Dillon area (I assume they are since I saw evidence of many of them in May of this and last year) and your small creek. Are you removing "native" beavers to enhance a fishery or property for development or, as suggested, they're harming the ecosystem of this creek?

I will completely agree with your first post about Patagonia since they are non-native and invasive. Here in my home town property owners and the electric utility are dealing with invasive non-native red squirrels. I HATE the damn tree rats; they steal walnuts from my tree and they cause utility outages (usually that particular tree rat is fried).

Beavers are quite the wanderers; I spent 28 years working on the mid-Columbia. Beavers use the Columbia to look for new lodgings and were quite adept. So good luck with your controlled removal.

Back to the original topic; that is the problem with man-made rock dams.

There is a significant difference between those dams and those made by beavers. Beaver dams tend to be in low gradient and smallish streams which at least here in PNW that are typically used by resident trout, anadromous coastal cutthroat and coho. While this time of year those dams may be impassable the migratory fish typically found in those habitats return during the fall and winter taking advantage of significant flow events to gain access past those temporal barriers. The man-made rock dams tend to be in more open river channels and lower downstream. At times those dams become impassable unfortunately some of the fish species attempting to migrate over those barriers (Chinook, bull trout, etc.) due so during periods of lower flows restricting their ability to by pass those barriers.

I have seen a number of cases where those man-made rock dams where indeed significant barriers. I recall an instance in late September on a bull trout stream where several dozen adult fish were holding in the pooling downstream one of those dams with several fish with their nose against the rocks. There was several miles of prime bull trout habitat upstream that was vacant of adult bulls. I took the time to roll a couple boulders out of the dam opening a passage way on my upstream. A hour later several bulls have moved pass that dam and others were lined up immediately below the "passage way". A week later following a cold snap the bulls were actively spawning upstream of that dam.

Curt

I've been a fan, and to a limited extent, scholar of the natural history observations that Lewis and Clark and their crew made during their trip across the western US in 2004-2006. When I give talks on the subject, I like to use a quote from Lewis about beavers and then ask the audience where they think the observations were made.
Here's the quote (his misspellings, not mine):

Lewis, July 24, 1805 -- "we saw many beaver and some otter today; the former dam up the small channels of the river between the islands and compell the river in these parts to make other channels; which as soon as it has effected that which was stoped by the beaver becomes dry and is filled up with mud sand gravel and driftwood. the beaver is then compelled to seek another spot …

this anamal in that way I believe to be very instrumental in adding to the number of islands with which we find the river crouded."

Where? On the Missouri river near present day Helena, Montana!!!