Conservation question

11 posts / 0 new
Last post
Crowriver
Conservation question

Hi everyone, and thanks in advance for fielding my question.

I live near, and fish in the Crow River in the NW metro. The Crow is infamous for high sediment and agricultural runoff pollution. I'm also hoping to help clean up the river. My question(s) is:

 

Would decreasing the sediment and agricultural pollution loads help increase, or even restore, redhorse spawning beds, and would this be realistically feasible through increasing the size of shoreline buffer zones?

 

Also, is removal of dams ultimately beneficial or harmful to native species like Redhorse? Is improved overall flowrate and subsiquent sediment outflow worth the risk of invasives (Silver/Bighead carp) taking over?

 

Thanks

Corey
Corey's picture
Conservation

 

 

To answer:

Would decreasing the sediment and agricultural pollution loads help increase, or even restore, redhorse spawning beds, and would this be realistically feasible through increasing the size of shoreline buffer zones?

Yes on both counts. Redhorse are lithophilic spawning species, like most suckers. They need clean, unsilted rock or gravel beds with free interstitial spaces between the rocks to reproduce successfully. Most of the silt and sediment that clogs up gravel beds comes from shoreline erosion, and increasing the shoreline buffer can certainly help reduce erosion. However, once the erosion is curtailed, it can take a long time for all the sediment to work its way out of a system.

Also, is removal of dams ultimately beneficial or harmful to native species like Redhorse? Is improved overall flowrate and subsiquent sediment outflow worth the risk of invasives (Silver/Bighead carp) taking over?

Great question. In most (but not all) cases, the benefits from removing the dam exceed any possible risk from invasive species. In some cases, especially where the invasives can interbreed with the natives (like with some native trout populations in the Western US) or where they can be very destructive (like the flathead catfish in some eastern US rivers) a dam can actually protect the native species from a very harmful invader. The dams in the Twin Cities do help protect the Crow from invasive Asian Carp, since they're downstream of the Crow and no Asian Carp have been found upstream of them. But dams upstream from the Twin Cities don't have any effect since they are already blocked by the dams below.

 

absentx
Not a scientist, just asking questions

Keeping invasive species in the equation, with dams removed, is it plausible that once-dominant (native) species would return to that form in most rivers?

 

In situations where dams are safe harboring native's from upstream invasives, is it also possible that a free flowing (blow up the dam) river over a long enough time frame would return all things to original intent? 

 

For example - I think if humans had nothing to do with Lake Michigan (and the entire system I suppose) for 1500 years, Lake Trout would again be the top predator. Thats a long time though...The dreamer in me says free flowing rivers would go back to normal faster than the super cold and super huge Great Lakes.

 

However, once the erosion is curtailed, it can take a long time for all the sediment to work its way out of a system.

 

You make that sound like a really long time. Are we talking years and years?

tom
tom's picture
Reference

Here's an article on dam removal on the  the Baraboo River. Simlar flows, terrain, geography, and climate. I think its a good reference point at least. https://whyfiles.org/169dam_remove/2.html

Corey
Corey's picture
It depends, of course

It depends, of course. If you take out a dam in the middle of the Mississippi River, say the Pool 4 Dam, it's not going to change much, even over time - it's just one factor in a severely altered river. If you take out Glen Canyon Dam on the Colorado it's going to change everything almost immediately - the dam is the single most important factor there.

 

As far as the sediment, that only really applies to the impounded area and below, and it only applies to the species who are obligate lithophilic spawners. In the Colorado, all that sediment would be a good thing - since the species there are adapted for large amounts of sediment that the dam has been unnaturally reducing!

 

If you read about some dam removals and/or fish bypass construction, the effect on fish migration is almost immediate, regardless of the sediment. On some of the Lower Yellowstone tributaries, species started showing up above the dam within weeks that had been absent for many decades! That's a very encouraging thing.

Crowriver
Thanks for all the replies

 

(sorry in advance this post is a tad too long) Thanks for all of the insightful replies - I work for 3Rivers, and for the past decade or so, we've been focusing a lot on native prairie restoration across the entire park district. Of course, restoring this native terrestrial habitat benefits countless species, both terrestrial and aquatic, as the prairie ecosystem supports shoreline ecosystems as well. 

 

3Rivers occasionally partners with MN DNR and the Bell Museum for eco/enviro impact studies on many species of terrestrial and aquatic wildlife, but so far rarely on native fish species, particularly non-game fishes. Last fall, Bell Museum hosted a state wide bio-blitz that included a sampling of fish species in Elm Creek within Elm Creek Park (no fishing allowed within park boundaries)- only small numbers of a few native species were counted, a lot of sediment and excess algae growth was seen, and no redhorse species were reported - apparently none have been reported there in decades. Also last fall, the Elm Creek Dam/weir project was completed on the Miss. at Mill Pond Park in Champlin (outside Elm Creek PR), where Elm Creek meets the Miss., to create a primarily game-fish stock pond for anglers (redhorse/suckers excluded). Just downstream of this mini-dam however, lots of redhorse can be seen, and caught, along with all the other popular gamefish, in the channel between the dam and the Miss. 

 

I'm wondering if all involved are missing the point of conservation, and restoration, by overlooking the moving water ecosystems. I believe if redhorse and suckers were reintroduced to Elm Creek, specifically within Elm Creek Park where they would be protected, the overall water quality would improve throughout the entire creek system, in and out of the park, along with all associated aquatic and terrestrial ecosystems. 

 

Bottom line (sorry took so long to get here): do native redhose/sucker species improve overall water quality in rivers, streams and creeks, and are there any scientific studies to prove it? If not, how to get this on the right enviro/conservation radar? I figured folks here might have some suggestions, as this seems to be a group of anglers that understands the value/importance of non-game fish in general, redhorse/suckers in particular. 

 

Thanks again! 

Corey
Corey's picture
Conservation

kernel j
Bottom line (sorry took so

Bottom line (sorry took so long to get here): do native redhose/sucker species improve overall water quality in rivers, streams and creeks, and are there any scientific studies to prove it? If not, how to get this on the right enviro/conservation radar? I figured folks here might have some suggestions, as this seems to be a group of anglers that understands the value/importance of non-game fish in general, redhorse/suckers in particular. 

More of an indicator species than panacea to improve water quality in most cases.  While they do covert a lot of otherwise inaccessible “food energy” (to other fish) from the substrate, the environment they are in determines the benefit of that.  Redhorse and suckers in general are one heck of a forage base in the streams I fish although it’s rarely mentioned or acknowledged.  I stubbornly maintain the success of “sculpin patterns” have a lot more to do with closely resembling the thousands of YOY Hogsuckers…which don’t hide under rocks most their lives.

 

So yeah, they are an vital and important element in stream health, likely in more ways than just the specifics above.

 

Also very likely you have plenty throughout the system where you think otherwise, I see it all the time around here (Indiana) in landlocked waters or partially/seasonally connected pits and ponds. However, the big populations and reproduction potential are really stream dependent and not likely you will change such in the waters you are working with.  They thrive where they can thrive and the requirements for Redhorse are pretty impressive in terms of food and sanctuary.

 

Good on you for doing good works.  Took a look at some maps of your area and looks to be a beautiful project regardless of how and where the Redhorse are or can be.  That little section betwixt the dam and the big river looks like prime Redhorse water.  If the dam wasn’t there or removed, it might not be as attractive to them as the stretch below would change considerably.  Strange, yet sometimes true depending on what’s upstream and how things go without the dams flow mitigating factors.

Corey
Corey's picture
Another Paper

I had this one referred to me by a researcher:

 

Henriksson, A., J. Yu, D. A. Wardle, J. Trygg, and G. Englund. 2016. Weighted species richness outperforms species richness as predictor of biotic resistance. Ecology 97:262–271.

 

Tyler W
A lot to cover

Wow. Looks like I am late to this one. But, it hits all my favorite topics: redhorse and water quality. 

 

Playing catch up: Corey is 100% on dam removal. Dams are mostly bad, but can provide refuge for native fish. Dams on our section of the Mississippi (and below) are all "run of the river" dams. They don't store water and don't alter the hydrologic cycle. They do trap sediment and alter habitat. 

 

Shoreline buffer zones are a tricky question. In general, I support them. But, I am not holding my breath. A major source of sediment is the river channel itself. Tile drainage of row crop is increasing the flow on Minnesota rivers. That is causing rivers to get deeper and straighter. As they dig themselves a new channel they liberate tons of sediment. Nothing (short of plugging the tiles) is going to prevent that. Buffers are great for reducing overland sediment inputs, but they aren't going to do much for stabilizing river banks. Anyone familiar with the Minnesota river knows that it has extensive protected areas along its banks (wide floodplain, National Wildlife refuge, etc) and its banks are constantly collapsing. The banks are covered in downed trees for miles! 

 

And yes, anyone who does a "restoration project" should consider hydrologic conuctivity and the historic movement of fish. Dams like the one you mention and others on Metro area streams (looking at you Locke Lake on Rice Creek) are limiting the spawning habitat of all river fish. 

Matt Miller
Matt Miller's picture
Dam removal & fish

Here's a story I recently wrote that may be of interest, on the impact of removing obsolete East Coast dams on migratory fish. In many instances, migratory fish like American shad and alewife return almost immediatley, and impressive populations can be restored.

The Living Benefits of Dam Removal