Save a Trout, Protect a Beaver

Updated: Jan 8

This piece was written for an English 2010 course at Utah State University taught by Natalie Christensen in April 2020.

Save a Trout, Protect a Beaver

While wandering the overwhelming isles of a fly fishing convention in Warren, Michigan, my little brothers in law came charging up to us like a herd of elephants. Their hands were full of free stickers, hats and promotional material from every booth they walked by and their faces had smiles ear to ear. On top of the stack was a bumper sticker that said “SAVE A TROUT, EAT A BEAVER” with a little cartoon beaver stamped with a general prohibition sign right over it. Many people from the crowds gave a perverted chuckle as they walked by the table of these stickers and some old timers grabbed them in strong support of removing these rodents from trout waters. Growing up in Chandler, Arizona it’s rare to hear any information about trout and especially rare for the topic of beavers, so this was my first time being introduced to the potential issue between the two.

Out of curiosity I began to wonder why there was such a cult following in the Great Lakes Region of hatred towards these ecosystem engineers. While reading online articles and forum posts from farmers, landowners and anglers I saw many complaints regarding beavers. Even the world-famous hunting brand Mossy Oak posted a How-to Blow-Up a Beaver Dam tutorial on their YouTube Channel. These frustrated keyboard warriors were stating that beaver dams keep water from flowing downstream to crops and grazing areas, block rivers with woody debris which stops migratory fish species and they say beaver activity mucks up waters destroying spawning areas while decreasing suitable habitat for trout. The information has spread across the United States and lead to people slaughtering beavers like they are ants at a picnic. From a quick glance, many of their concerns seem warranted but there are always two sides to every story, and I prefer those with research to back them up. Numerous studies done on the interaction between beavers and cold-water streams have shown that in many streams, beavers are actually beneficial. From my research I found that water storage by beaver dams creates consistent water supply, studies showed that migratory fish are not impacted by beaver dams and beaver activity is beneficial to salmon and trout populations. The fact of the matter is, every side of this argument wants a healthier watershed for their own reasons and the abundance of scientific research has convinced me that to reach this goal they need to work with the beavers.

In my personal experience of working with farmers and landowners they are often very set in their ways, so it was no surprise to me when I read their very opinionated comments about beavers. Stories from the past told tales of blowing up beaver dams with dynamite, trapping beavers for their fur and poisoning the rodent to stop their construction in the rivers. When your livelihood depends on the water coming down river, any type diversion is assumed to be their enemy. Water is key to survival of livestock and agriculture but is there any merit to their claims that beaver dams are depriving their land of water? It is obvious to anyone who has seen a beaver dam in person that they create still like pools and prevent the flow of water maintaining its previous pace downstream causing storage. This concept has been replicated on nearly 3 million miles of rivers and streams in the United States with over 91,000 dams. If water storage by dam is such a bad thing then why would we replicate it so many times? I decided the best way to answer my questions was through peer reviewed research.

 Photo by Aaron Smith
Brook Trout and beaver ponds are a common combo

Eco geomorphologist, Fluvial Scientist and Restoration Practitioner Dr. Joe Wheaton found that the storage of water by beaver dams is not just in the ponds but is in its ability to raise the water tables. The water table is where groundwater would typically sit and be used by vegetation. This spreads water through the whole valley bottom, which is low area between hills or mountains where the river flows through. Raising of the water table allows the water to be absorbed similar to a sponge and then slowly releases that water through the long hot summer (Partnering with Beaver 2015). As I was scouring publications, I found that beaver dams are shown to stabilize stream flows and increase sediment storage in the pond which is beneficial to downstream water users (Lokteff et al.2013). Sediment and nutrients stored by beaver dams is recruited by streamside vegetation to aid in supporting new growth and released over time to be a more beneficial slow spread of nutrients and less of an impact caused by sediment transfer on the watershed. A study by Alan Puttock on sediment and nutrient storage in beaver ponds showed beaver dams may help to reduce the negative off-site impacts of soil erosion and diffuse pollution from agriculturally dominated landscapes (2018). A prime example of this is intensively managed or over grazed grasslands.

In some water diversion situations, rivers are overused for agriculture, grazing or culinary purposes causing the river to run dry for part of the year. The storage created by beaver dams prevents streams from becoming cut down into the stream bed which looks similar to a v shape and disconnecting from the water table which often results in a loss of flow during the summer. By having this storage of water in beaver ponds it makes a more reliable watering source for downstream users. This consistent flow of water also feeds the valley bottom providing a better forage base for cattle grazing and native wildlife. (Partnering with Beaver, 2015). Wheaton and his partners have used Low-Tech Process-Based Restoration to aid multiple land users in employing beavers to recover their once promising agricultural land. That being said, the difference between a beaver’s natural process of building dams and manmade structures of concrete can be significant in cost and by the impact on native fish and wildlife.

Searching for beaver pond residents

As far back as I can remember, I have seen dams in the news with a major complaint being they prevent fish migration. It’s not typically the storage of water that people are upset about but rather the impenetrable concrete barrier putting a halt to upstream passage. The steady decline of salmon and steelhead populations have created an outcry that something needs to change and much of what is being demanded is the removal of dams. Stickers with messages like “Free the Dam Rivers”, “Free the Snake”, “Dam Politicians, Not Rivers” cover rusty bumpers, windows, boats and even signs like graffiti. The film Dam Nation (2014) by Patagonia highlights graffiti on the Venture river’s Matilija Dam depicting a dotted line and scissors as a protest in favor of tearing it down. A quote from the film states “You can take half of a salmon fishery, eat it and it will keep replacing itself. What kind of a species throws that away?”. The comment was referring declining populations of salmon which they feel is caused by these dams. There is no argument that the cement barriers created by man put a stop to fish migration and have been incredibly detrimental to native salmon and trout. The question I had was, what about those who believe that beaver dams have the same impact?

During my research I came across numerous studies done on the interaction between beaver dams and anadromous or fluvial fish, like salmon, steelhead and cutthroat trout. These fish rely on migration from large bodies of water into streams where they are in search of suitable habitat to spawn. Construction of wood structures in the water by beavers is said to limit these fishes ability to travel further upstream and obstructs their reproduction productivity. Even in small streams, beaver dams have reached over 8 feet tall and it is logical to assume that they may act as a barrier (Kemp et al. 2012) but in the words of a teacher I once had, “There is more than one way to get to Circle K”. That phase was repeated daily to a variety of students that were not open minded in hopes of sparking some creativity into their thinking. In the sense of fish migration, there is not just one way to move past a dam and to quote the movie Jurassic Park, “life finds a way”.

A fluvial fish coexisting with beavers

Results from a study I read about a stream only twenty minutes away from our campus by Lokteff at el. showed that native species of trout in the United States, for example cutthroat and brook trout, which evolved with the presence of beavers were not impeded by beaver dams (2013). Brown trout, which are native to Europe and introduced to North America in the 1850’s for sport fishing opportunity, have been shown to have less success passing beaver dams. This may be useful in aiding in the recovery of native trout populations where the invasive brown trout are present. Many of the trout species native to the Western United States have adapted to spawn during the Spring. During this season, high river flows cause beaver dams to fail or rivers to create side channels that act as fish ladders around barriers allowing access for upstream migration (Lokteff, 2013). In Utah, fisheries biologists used pit tagging to track the movement of native cutthroat in areas with beaver dams. Their data showed that cutthroat trout not only passed through beaver dams, but they often did so up to a dozen times a day. For all native species, including the fish who spawn in the fall during low flow periods like salmon and brook trout, the diversity of flow paths over, through, under, and around provide possible pathways for upstream travel.

Stream Restoration specialist Dr. Nicolaas Bouwes found that following the installation of beaver dam analogs, which mimic beaver dams, they observed significant increases in the density, survival, and production of native juvenile steelhead trout without impacting upstream and downstream migrations (2016). High spring flows may have negative effects on beaver dams causing them to fail but it was discovered by Bennett et al. that both the construction and failure of these dams appear to create new spawning habitat which is quickly taken advantage of by trout (2014). This creation of spawning grounds and ability to move past dams disproves the theory that beaver dams are decreasing spawning success for trout and putting a halt to migration.

Beaver pond in Spawn Creek, Utah

From this research I learned that there are other variables in impact that beavers have on trout populations, one of which is due to the steepness of the stream. In steep gradients, beavers are shown to actually improve stream habitat, filter sediment causing more favorable conditions in between dams and provide habitat to increase the number of aquatic invertebrates which is primary diet of trout. The introduction of woody material improves habitat complexity while providing protection from predation and the water storage from beaver dams reconnect flood plains promoting vegetation growth. Beaver dams are actually increasing the quality of habitat for fish and can result in larger fish sizes. Many anglers state that a beaver pond on a summer day can provide excellent fishing opportunity.

In low gradient streams, beaver dams have been said to decrease quality of habitat, reduce dissolved oxygen levels in the water and increase water temperatures (Wisconsin Beaver Management Plan, 2015) but studies on these streams have shown there is minimal impact on trout populations. This may be due to the fish’s ability to migrate in search of more favorable habitat. While a natural balance between native fish and beavers has always existed, human impact has caused a reduction of natural predators of beavers in many places. Predator control before regulations on hunting had drastically reduced predator populations and by 1931, large carnivores had been mostly eradicated east of the Mississippi River (Slagle 2017). The development to more urban style areas has also displaced remaining natural predators and allowed beaver to become a nuisance when backing up storm drains, causing flooding into unwanted areas and harvesting aesthetic vegetation. Without natural predators of beavers, the scale has been tipped causing large populations in the mid to eastern United States which has in turn led to a need for reduction through harvesting these animals.