April 04, 2016

Beaver Dams

They typically back up water when they are first built and mean lots of trout for the angler.

The WDNR shocked a huge brown out of this dam a couple years running.  The land owner told me about the 29 incher he had on his wall that he discovered while he went along on a shocking trip. This stream had a thriving brook trout population but is protected these days due to gill lice.  No brookies are allowed to be harvested due to the scourge that is gill lice.

The PH changes in long established dams and is typically detrimental to trout.  Dams also block seasonal spawning. Dams are breeding grounds for gill lice. The biggest male small stream brown I have ever seen was caught behind this dam.

 I caught 24 brookies at this dam and never moved from my casting spot. This is one of the streams that no longer supports brook trout due to gill lice.

The beavers have had this dam for 2 years now on the headwaters of one of my favorite streams.  The spring that supplies the life to this stream is only 80 yards upstream of this massive beaver dam.  The water spreading out over a larger area gives the water more surface area and warms the water way artificially and it could have long term detrimental effects on the trout population.

Dan Braun and I had a veritable field day behind this small dam slamming brown after brown.


Not a single trout was caught behind this warm stagnant dam this day.

 This stream was my best brook trout stream and it now has none.  It was also a big time tiger trout stream and no tigers there now.

 Beaver dams long term are not an angler's friend.  Beaver runs can be way dangerous to step in and the pongee sticks the beavers leave behind can impale an angler.


Beaver dams are not good for the stream and you should contact the WDNR and tell them about dams you have found.

Gill lice thrive in beaver dams.

Please contact the WDNR when you find a beaver dam.


  1. I'm convinced that it is the beaver's ambition to kill as many anglers as possible by impaling us on those spikes!

  2. I can make those beaver disappear. Protect the trout and tbe beaver make great summer sausage.

  3. Len,

    You think Beaver dams are a scourge on a spring creek you should see what they do to the freestone streams in Northeast Wisconsin. They are a devastation to the trout population on the long term. Good fishing behind the pond for about 3 years and it all silts in...game over!

  4. So how did beaver and brook trout thrive together for so long? Not saying beaver dams can't harm a stream, just a question.

    1. was told by fisheries folks that beaver dam were optimal breeding grounds for gill lice, they also said the almost extinction of brookies from decades ago was from gill lice. gill lice have been here a long time.

    2. So have the brook trout and beaver, and they're all still here (at least for now). There are definitely problems, and the presence of brown trout certainly doesn't help. My point, however, is that we base all sorts of conservation strategies around what we think is correct and appropriate, often without thinking first about how things would be if we weren't here and weren't managing. The question to ask is, "if brook trout (or any species) and beavers have co-existed for so long, what role do they play in the ecosystem, and how do they affect each other, positively or negatively?" Tons of conservationists are starting to realize that beavers can have a huge positive impact on watersheds and ecosystems. For instance, they're being used in the John Day watershed to help wild steelhead populations bounce back. They've found that beaver dams rarely prevent upstream migration of fish, and that smolt are able usually able to penetrate the dams. We also talk about un-natural levels of phosphates, etc., in water due to agriculture, but beaver dams help filter out excess nitrates and phosphates from streams, preventing eutrophication. Just saying, we need to look at the whole picture.