Don't kid yourself, beaver dams are temporary partial barriers, they don't compare to a real dam. They actually increase subsurface flows and moderate temperatures in the whole system, but yes summer water temperatures, especially in the sun, can be increased... offset by other benefits.Originally Posted by Silver Creek
Dead trees add habitat critical to trout. There is more water available to surrounding trees and edged with vegetation.They kill trees in the flood plain by drowning their roots. This happens in a little as 6 months. This removes overhead shade, further warming the water.
Beaver dams are temporary. I doubt there are any population effects- trout upstream of the dam can still spawn and those that are downstream and can't pass; they spawn elsewhere. They are rarely complete barriers anyways.They prevent upstream migration of trout to their spawning areas in feeder creeks. Less spawning areas = fewer trout. Any increase in trout biomass is temporary until thermal pollution and spawning losses take over.
The deposition of sediment and organics in the slow moving areas of beaver dams creates excellent soil material. Perfect meandering channels form through filled in beaver ponds creating lush streams with stable banks. And the process continues.They build riparian areas? If you mean by "riparian" a pond then yes. If you mean a river, then, nope! What they do is widen the and destroy rivers. Dams increase still water not moving water.
They do build a flood plain - great for ducks and water fowl, bad for trout in the long run.
Have you measured the O2 above, through, and below? Depending on the gradient of the stream, water trickling over and through a dam or series of dams can have a very positive effect on oxygen levels. My point is that it is not always a bad thing.The improve aeration at the dam? Really? Does that make up for the aeration lost over the expanse of the dam? Nope. There is a net loss in aeration when running water is replaced by still water.
Trout stream management does not mean doing what is best for the trout, it is a balance for landowners, rec users, wildlife, and sportfish. Reread the last line... "even though these activities have resulted in questionable success rates in trout habitat improvement".Only in high gradient (mountainous) flows or where the average water temperature remains too cold (high altitudes) are there benefits to a beaver dam. Here they can form areas of trout water where there is little and delay runoff to even out the runoff. At high altitudes the warming of ice cold runoff by a beaver dam can benefit trout by increasing insect life in the pond and the water below. But in Wisconsin and the eastern USA, beaver dams are a net negative as the following body of research shows.
See the following Cold Water Fisheries research from the Wisconsin DNR and the University of Wisconsin College of Natural Resources on the effects of beaver on trout streams:
Research paper by Ed Avery of the Wisconsin DNR Cold Water Fisheries Research Center:
http://dnr.wi.gov/org/es/science/pub..._RS_731_91.pdf
http://www.amazon.com/temperatures-n.../dp/B0006DBYD8
"Much of Wisconsin's current trout stream habitat management focus on implementing in-stream structures and bank stabilization, beaver dam removal, and streambank debrushing even though these activities have resulted in questionable success rates in trout habitat improvement."
This is a 20 year old document for an wildlife damage control conference.http://www.uwsp.edu/cnr/wicfru/Research/Cross.aspx
"Beaver (Castor canadensis) dam building activities create many longtern affects on stream ecosystems. Beaver dams may negatively influence trout fisheries by creating physical barriers to spawning areas, increasing sediment retention, and increasing water temperatures. The U.S. Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) Animal Damage Control (ADC) program in Wisconsin, entered into cooperative agreements with the Wisconsin Department of Natural Resources (WDNR) and the U.S. Forest Service (USFS) on the Nicolet National Forest from June through September,b1988, to remove beaver and beaver dams from priority classed trout streams."
http://digitalcommons.unl.edu/cgi/vi...context=ewdcc4
This is a newspaper article"One of the biggest challenges facing stream restorers now is the overabundance of the beaver. With trapping rates lowering over the past few years, the beaver population keeps growing, as do their dams.
Monitoring is really helpful is getting information reported about beaver dams, which devastate the trout streams, Hlaban said. I'm sure there are a number of dams we wouldn't have discovered if it wasn't for stream monitors being in there and understanding what to look for."
Trout Unlimited Chapters receive special written permission from the state DNR to trap on public land or permission from the owner of private lands to trap beavers during the offseason."
http://watermonitoring.uwex.edu/pdf/...utdoorNews.pdf
http://www.wisconsintu.org/LinkClick...bid=58&mid=372
"kids only zone" on a website."Since the trout stamp began in 1978, the DNR has restored more than 750 miles of trout stream, kept more than 700 miles free of beaver dams and maintained the good condition of many miles of trout streams throughout Wisconsin."
http://dnr.wi.gov/news/DNRNews_Artic...kup.asp?id=459
"Beaver dams cause trout streams to become silted and warmed. Dams prevent trout migration and result in a lowered trout population."
http://www.timberwolfinformation.org...web/beaver.htm
Much peer reviewed research today will tell you that beaver dams increase fish species richness, especially in slow water streams. They are temporary and partial barriers, they do have some negative effects, but a net positive impact on the fishery... the biggest issue is that they have to be left to fill on their own. In areas where beaver dams have been managed, you'll have to keep managing the dams... you've created a man made issue that can only be fixed by letting nature take its course- beaver dam succession.
You will see a false positive when dams are removed- you've temporarily increased flows (flushing flows), you've instantly changed the temperature, you forced forge fish (fish food) into marginal habitat> increasing prey availability to trout, you uncover coarse stream beds (flushing downstream and up), and you've forced trout to redistribute in the stream. But to get that affect you have to allow beavers to build a dam and then remove it. A stream not allowed to change will stagnate, diversity will drop, and anglers will leave.
I'm not saying it is all bad, I'm just making a point, that, there can be a net benefit if the system is allowed to naturally grow.
We tried to stabilize banks here with log cribs... now it is a worse problem because they are all failing. We have had (and still have) beaver dam removal programs... those streams are starting to stagnate.
1955 Rupp (AFS- BEAVER-TROUT RELATIONSHIP IN THE HEADWATERS OF
SUNKHAZE STREAM, MAINE) found:
1955 and those aren't bad results, especially considering the increase of food to brook trout.ABSTRACT
The effect of beaver, Castor canadensis(Kuhl), on an eastern brook trout,
Salvelinus fontinails( Mitchill), population was studied in the vicinity of five
beaver dams in the headwaters of Sunkhaze Stream. The beaver dams were found to present a serious obstacle to trout movements but they were not a complete barrier. Estimated unit-area production of bottom organisms was poor in the beaver ponds but the beaver had so increased the bottom area that total production of the stream section was probably more than doubled. Forage fishes appeared to be somewhat more abundant in the beaver ponds than in the open stream and constituted an unexpectedly high percentage of the food of 6- to 10-inch brook trout taken in the ponds. Measurable but not serious waterquality reduction was found in and below the beaver ponds.
In North Dakota SCHLOSSER and KALLEMEYN (2000) found that(sorry I don't have an electronic copy).The presence of a productive and diverse fish assemblage in headwater streams
of north-temperate areas requires the entire spatial and temporal mosaic of successional habitats associated with beaver activity, including those due to the creation and abandonment of beaver ponds.
And the 1998 paper by Snodgrass and Meffe from S. Carolina>(INFLUENCE OF BEAVERS ON STREAM FISH ASSEMBLAGES: EFFECTS OF POND AGE AND WATERSHED POSITION-sorry no electronic copy either)beavers have a positive effect on fish species richness in low-order, blackwater streams, but maintenance of this effect requires preservation
of both spatial and temporal dynamics of beaver pond creation and abandonment
A paper from Sweden showing the benefits of beaver ponds to Brown trout:
http://www.sciencedirect.com/science...168d01fb2404f1
(Effects of beaver dams on the fish fauna of forest streams. H?gglund and Sj?berg 1999)
Reply With Quote