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Message Subject: Interesting Read/info.

walleye express

Posted 7/28/2015 8:17 AM (#113396)
Subject: Interesting Read/info.

Member

Posts: 2680

Location: Essexville, MI./Saginaw Bay.

The Historic River watersheds that feed Saginaw Bay used to be spawning nurseries to many natural fish species. Electric Power Dams became the first culprit to lower then halt many natural reproduction opportunities for fish species. Then pollution killed off a lot of what was left. A lot of things have changed since and the science to successfully change them back to productivity can be complicated and intriguing. I delighted in hearing that one of our older Dam/Spillways in one of the smaller rivers that make up the Saginaw River Drainage, was going to be modified and made more walleye friendly for their spawning needs. My good DNR biologist buddy e-mailed me with a more conclusive prognosis that I found interesting. First view the TV report then his e-mail.

http://www.abc12.com/home/headlines/Construction-to-start-next-week...

Dan:
I too, greatly share any enthusiasm for improving fish passage in the Saginaw Bay watershed. I maintain that dams and spillways are one of the single biggest detriments to our fisheries today.

There are three options when we have a dam on an important spawning tributary (1) remove the dam, (2) try to construct some sort of passage/ladder type solution, or (3) just accept the loss/impact to fish reproduction.

Dam removal always has the best outcome in terms of fish reproduction because once gone, there is zero impediment to fish movement and the downstream passage of spawners (once done spawning) and their fry (once hatched) is unaffected. People often forget about getting fish back down stream too in these situations.

Fish ladders and other passage options are a compromise. No passage design is 100% successful but can still be a great improvement over just accepting the dam as is. Rock ramps as a fish passage design has gained popularity in recent years. They are an option for low head dams or spillways. The concern I have is that they have not been very thoroughly evaluated in every instance and those that have been evaluated, have had very limited success in passing fish. Dam owners, however, are very excited about rock ramps as they have the appearance of mitigating the negative environmental impacts their dam has on the fish community. Because of this, I continue to have of a lot of skepticism over rock ramps and their efficacy in truly passing fish.

The idea behind the ramp of course is that instead of being confronted by a vertical obstacle, the ramp makes a sloping run of water or rapids that fish will navigate. Fish, however, have proven finicky over their willingness to try and navigate rapids. Salmon of course are famous for that, but most of our native species in the Great Lakes didn’t evolve with that sort of reproductive strategy or perhaps drive and usually won’t or simply physically can’t jump up stream.

The trick with rock ramps is that they have to be carefully constructed and positioned to get fish to use them. Then they need periodic evaluation and adjustment/tweaking to continue to promote fish passage. Few of these ramps are getting this sort of follow up. The rock ramp at Chesaning (Shiawassee) Has gotten some follow up. Initial reports said that it was failing to achieve any fish passage. More recently, it seems after a few winters the ramp pools have been disrupted by ice flows and are now actually doing a better job as starting to pass some fish (like walleyes). So it may be that these structures need to “go natural’ for a time to become useful.

What has been observed is that the rocky flow at these ramps has proven to be attractive to spawning fishes so they just spawn in the ramp or the run-up to the ramp. That’s not a bad thing, but then it’s really just a habitat improvement structure not a fish passage structure and its utility is limited to how large it is and even though they are big structures, they are not likely making up for all the lost access to river miles above the dam.

So my take on rock ramps is; better than nothing, but not as good as full removal. They require careful planning, design, construction, evaluation, and follow up. The issue of fish passage in the Saginaw Bay watershed and all of the Great Lakes is an issue that still needs more attention. It’s a socially and economically complicated issue. Many dams create waterfront property (reservoirs) that homes have been built on. Some dams serve legitimate modern day needs of hydroelectric power production and flood control. Many however, are decrepit, antiquated, and no longer serve any real purpose. Many of the reservoirs behind them have become warm, silty marshes with little fishery qualities. Most dams were built around in the early years of the Twentieth Century. That means they are at or passed the life span of the structure and now pose a hazard or great expense.

Many of the dam owners (not all) will abandon them or declare bankruptcy leaving their fate to the state to pay for (repair, replacement, or removal). Dams in Michigan are licensed by DEQ and the federal government is in on their regulation too. Not every dam has a significant impact on fish reproduction by many do, especially the first barrier upstream from the lakes. Complicating matters, the US Fish and Wildlife Service (the sea lamprey control division) very much depends on dams as part of their control strategy. In fact the sea lamprey control folks would like to see more dams, while other parts of the USFWS is working to restore fish passage and connectivity. You can quickly see how this issue gets complicated.

I remain convinced that full recovery of a lot of our species (lake sturgeon is a prime example) will hinge on progress on dam removal statewide. I suspect progress will come one dam at a time. For the state, we have mostly been waiting patiently for dam owners to come to us when their dams finally get too aged and we will try to work with them to find the right next step, often that is in fact removal. There are a lot of funds out there to help with that. Michigan has seen a number of very successful dam removal projects where the state, dam owners, and municipalities were all partnered. I guess I feel like communities need to see dams for what they are. Man-made structures from an earlier time in our history and ask if this is really serving the larger good for their communities. Most dams and reservoirs have been around long enough that no living person can remember what it was like before them, but behind each dam, under each reservoir is a free flowing river (sometimes even with white water or waterfalls) that is waiting to be reborn and attract fish and give back to the local community in ways that few have probably recognized.

Edited by walleye express 7/28/2015 8:35 AM

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