Studies show that hydraulic dams are harmful to fish. Walleye have suffered for 50 years in the Kawarthas. As a taxpayer, demand we use stop log dams.

Hydraulic dams are killing the fishery, so what are we doing about it?


  1. Trying to get more water year round
    2. Trying to get the TSW to use stop log dams.

This requires both the MNRF and the Trent-Severn Waterway to change operations to protect our dying lakes.

Below is the

  • Ministry of Natural Resources and Forestry’s Fisheries Management Plan (from which nothing has been done)
  • Ministry of Environment’s press release announcing the quarter of a billion dollars given to the Trent-Severn Waterway for infrastructure repairs ($0 of which the TSW said will be spent to repair the natural infrastructure below the dam—the lakebed),
  • MP Barry Devolin’s Householder distributed to over 50 000 households that shows where the $90M for this area was allocated
  • Watersheds Canada Walleye Habitat Toolkit, which outlines how best to improve spawning beds in Ontario. 

2009 Ministry of Natural Resources Report outlines what needs to be done to Save the Walleye. The mid-term review (2014) was never released. Requests to release the data are ignored. Nothing has been done!


This is the Fish Habitat Toolkit put out by Watersheds Canada. It’s a great blueprint if we ever stop hitting roadblocks everywhere we turn.


Ministry of the Environment press release, 2015. It outlines the quarter of a billion dollars given to the Trent-Severn Waterway to improve infrastructure. Former MP for Haliburton—Kawartha Lakes—Brock, Barry Devolin, was instrumental in getting the TSW this much-needed money.

We asked the TSW to cover the cost of the Bobcaygeon and Lindsay spawning bed environmental analyses (for the Parks Canada Research Permit) and the cost of the in-water enhancements. The response: “there is no money for that.”

In 2015, former MP Barry Devolin helped get the TSW $250 million to improve infrastructure. In Bobcaygeon, $600K was for the lock, $450K for the dam. Out of $450k for the dam, $0 was allocated to repair the spawning bed directly in front of it.

$1 million was given to the TSW for updated water management and water/weather monitoring equipment. We want at-site monitoring using hydrodynamic water models and equipment similar to that used in other navigation systems like the Rideau Canal (real-time data of water levels for real-time response) to maintain the minimum water levels people (and fish) expect in this area!


Below are studies provided by Kawartha Conservation and Sean Berger, an anthropology graduate student from Trent University studying historical ecology in the Kawartha Lakes:

1966 Report: Ministry of Natural Resources (Lands & Forests) Bobcaygeon Spawning Bed

In 1966/67, the Ministry of Natural Resources (MNRF), then Lands & Forests, released a report after experimenting with ways to improve the Bobcaygeon spawning area. In 2018, Peterborough MNRF stated that the report is too old to use as support for our project, as if 50 years changes how fish behave. Of all of the studies listed below, this report was one of our most important finds. Excerpts are provided below:

“The area below the dam has long been known as an important spawning ground of walleye several thousand of which congregate at this location each year during the spawning run.” (1966)  

The days of thousands of walleye gathering for spawning are long gone. In 2018, there are a barely any walleye left at all.

“The population level of any species is the expression of the effects of the environment on the species. Obviously it is axiomatic that the most successful means of increasing levels of a species is to so manipulate certain unfavourable components of the environment that the desired effect is achieved….The purposes of this paper are to describe the results of two experiments to improve the spawning facilities for walleye (Stizostedion vitreum) in a known spawning area below the Bobcaygeon Dam.”

The MNRF knew what it was doing in 1966. It’s a shame this knowledge and willingness to work didn’t survive through the decades to enlighten Peterborough MNRF management.

In the 1980s, the MNRF dumped aggregate on the Bobcaygeon spawning bed, raising it up even higher. We want the MNRF to correct their own mistake, help us enhance the spawning area, and start managing this fishery like tax payers expect.

“In order to ensure that a current of water passed over the sections, one log in the sluiceways of the dam directly upstream from the experimental area was removed.” 

This is exactly what we have requested from the Trent-Severn Waterway! Remove 2-3 logs from 2-3 of the most northerly stop log dams directly in front of the spawning area! It’s a no-brainer. Yes, it requires some manual labour, but you only have to do it once. 

2008: Fish Response to Modified Regimes in Regulated Rivers: Research Methods, Effects and Opportunities,  Departments of Biology at Carleton and Ottawa Universities, Murchie et al.

A big thank you to Sean Berger, an anthropology graduate student from Trent University studying historical ecology in the Kawartha Lakes, for finding this local report. It is a synthesis of 123 reports pointing to the same conclusion: modified flow regimes in regulated rivers are affecting fish and fish habitat.

Studies emphasize the need to sustain high flows (Paukert and Fisher, 2001), or to at least provide stable flows that are of sufficient duration and discharge to allow for spawning, larval development and juvenile residence (Freeman et al., 2001)… The need to mandate ecologically acceptable minimum flow levels and eliminate or reduce pulsed flow operations is widely recommended. (Dejalon and Sanchez, 1994)” 


“Of the 99 studies that conducted statistical analyses, 73.5% resulted in statistically significant effects of flow modification on fish and/or fish habitat.” 

That’s a lot of studies all pointing to the fact that the hydraulic dams on the Trent-Severn Waterway are significantly effecting walleye and walleye habitat. It’s time to make some minor changes to mitigate the damage being done! All we’re asking for is a minimum flow, a minimum water level, and an increased dependence on stop log dams to achieve both these things. Fish deserve enough water to survive. The walleye aren’t getting it on the Trent-Severn Waterway.

“When flows are enhanced by establishing a minimum flow after regulation, various studies found that populations responded favourably to the conditions. Travnichek et al. (1995) found that an enhanced flow regime (implementing a minimum and consistent flow release) supported more abundant and diverse fish community assemblages, with the abundance of fluvial specialists increasing to over 80%. Also, a number of authors observed an increase in the number of alien species and reduced species diversity in increasingly regulated catchments.”

There is hope! If we provide walleye with a minimum flow regime with consistent flow (not raging torrent followed by complete shut off) the walleye will come back. Despite  studies that describe the harm that the Trent-Severn Waterway is doing to the fishery, the MNRF said it can’t support fixing the spawning beds because there’s no way to prove doing so would have a positive impact on the walleye population! Common sense dictates that increasing water levels and flows such that the spawning beds are under the water will have a positive impact. Walleye counts would also be a logical way to measure success, but the MNRF does not conduct walleye surveys and will not use the walleye count data provided by Lindsay Bassmasters, volunteers who do this job for the MNRF Peterborough office. 

“…the majority of studies identified that there were statistically significant effects of flow modification on fish and/or fish habitat…Generally it appeared that modified flow regimes in regulated rivers could be responsible for spatial transitions in species assemblages, reduced recruitment, and alterations to spawning migration timing.” 

The TSW modifies flow regimes down to the lake bedrock. The spawning beds are out of the water. For five years we have asked that enough water be held back to cover the spawning beds. In all but one year water did not cover the spawning beds throughout the duration of the spawning season. We saw no spawning success! Fish can’t survive out of water. The seagulls had a heydey and the rocks turned yellow with unviable eggs.

The TSW makes changes and doesn’t monitor the effects of those changes in real time. Why don’t we use some of the $1 million given to the TSW to determine the minimum flow regime (depth and velocity) necessary to maintain fish resources? At-site equipment for real-time water level information back in the office! How else will they know what’s going on?

In 2018, one log was pulled from 2 stop log dams on the north side of the river. But the hydraulic dams on the south side were open so wide that no water spilled over the top of the stop log dams. Volume calculations were made without consideration of spatial distribution. No one monitors how these changes physically play out. It is 2018. Surely there are real-time monitors available to tell the people with calculators 50kms away what’s going on?

UPDATE: a camera was installed on the dam in 2020. However, there are technical problems—it doesn’t work.

“Due to hypolimnetic dam releases [hydraulic dams that open at the bottom], yearly fluctuations in water temperatures were observed to differ from neighbouring rivers or up-stream and down-stream reaches (Cambray et al., 1997)…high-pulsed flows were correlated with lower than normal downstream water temperatures” 

The MNRF will tell you this is not the case. Of course, this comes from the same staff who say that there’s no way to determine if putting water over the spawning beds will increase the number of fish who show up to spawn. 

2012: Assessment of the Effects of Habitat, Harvest and Community Interactions on the Abundance of Walleye Sander Vitreus in Inland Lakes Throughout Ontario, Holden. 

The MNRF uses “fishing pressure” as the reason why walleye have declined. Certainly walleye is a popular recreational fish. But this statement is met with much frustration as fishing tourism has all but died in the Kawartha Lakes. There is no fishing pressure because there are no fish left. American tourists used to come by the thousands every summer.

According to the MNRF’s own data (Kawartha Lakes Fisheries Assessment Unit, 2016), angling hours dropped from 175,000 hours for walleye in the 1980s to just 34,000 hours in 2013. This is not because anglers don’t want to fish walleye! It is because there’s barely any walleye left to catch. Fishing is so hard now that many people have stopped fishing. Total angling hours for all 4 fish species studied (musky, bass, walleye, and panfish) is less than the angling spent on walleye alone 30 years ago. Thirty years ago, people of all ages loved to fish. Now, only those who remember what it used to be like still try.  Also, white sucker has decreased at the same rate as walleye and there’s no fishing pressure on white sucker.


“Centrachid species [like bluegill, perch, and crappie] may affect walleye populations through direct predation on walleye or through exploitative competition. Juvenile centrarchids have been identified as a significant source of mortality on stocked walleye (Hoxmeier et al. 2006)…Schiavone (1985) attributed the collapse of the walleye fishery in the Indian River Lakes, New York, to the introduction of black crappie… Walleye fisheries may need to be managed more cautiously in order to maintain stocks at higher levels to maintain a top predator biomass large enough to suppress potential fry predators.”

That is exactly what has happened in the Kawartha Lakes. The panfishery has exploded since 2001. For every 2 walleye in our lakes there are over 305 panfish (as of 2012). This number is likely even higher in 2018 as walleye numbers continued to decline. What is the MNRF doing about panfish predation of walleye eggs? Nothing. What needs to be done? Stocking of fingerling walleye to put the balance back in check.  

“Direct predation may also be mitigated when walleye are in sufficient abundance to maintain fry predators at levels that prevent depensatory [a decrease in the breeding population leading to reduced production and survival of eggs or offspring] efforts… Bluegill, pumpkinseed, and smallmouth bass were the centrarchid species that were significant negative predictors of walleye abundance…Lakes with bluegill or black crappie had consistently low abundance of both walleye and white sucker…Bluegill densities exceeding 50 kg/ha have been linked to walleye recruitment failure and lab studies confirmed that bluegills are effective predators of walleye at the egg and fry stages (Schneider 1997)”

We need to stock fingerling-sized walleye to bring back a sustainable biomass and balance out the out-of-control panfishery. 

“White suckers are a species that has similar thermal preference and spawning habitats as walleye but is not exploited to the same degree in the recreational fishery (Scott and Crossman, 1979). An exploratory analysis was conducted to compare walleye abundance and habitat to white sucker abundance using a linear regression… Spawning habits of the two species often overlap both spatially and temporally and it is common to capture both white sucker and walleye fry in the same sampling gear (Corbett and Powles 1986). It would be expected that if angler harvest were the largest factor in determining walleye abundance, white sucker abundance would show a higher correlation with khab than with walleye abundance since white sucker abundance would be more reflective of habitat conditions. This however was not the case. It would appear that factors limiting walleye abundance act in a similar manner on white sucker populations. While causation cannot be directly inferred, lakes with the lowest abundance of both species have one or both of black crappie and bluegill present which supports a fry predation hypothesis.” 

The MNRF say that fishing pressure is to blame for the collapse of the walleye fishery. If this was the case, why keep issuing licences for walleye? But fishing pressure is not the major cause of the dwindling walleye population. Walleye recruitment is lower and lower each year because low water levels prevent walleye from reaching their historical spawning areas year after year. If some walleye successfully spawn, the water drops before the eggs hatch, exposing the small percentage of eggs that may have hatched. To make things worse, panfish prey on walleye. With such a critically low biomass of walleye, what is left of the walleye population after the Trent-Severn Waterway has done its harm, is made worse by panfish predation. What makes matters even worse is that the TSW is approving installing hydro stations on the dams. How do we fix all of this? Higher water levels, lower spawning beds, and fingerling-sized walleye stockers put into Sturgeon Lake. 

A closer look at what some of the studies listed above say:

2011: The Case for NPDES Regulation of Dam Discharge, Enion

Dams can logically be separated into three components: the reservoir behind the dam, the dam itself, and the discharge downstream from the dam. Each component and the interactions between the components cause environmental effects. It is an understatement, however, to say that hydroelectric dams have environmental impacts. They have the potential to completely transform the ecology and hydrology of a river or stream. Dams have played a major role in the destruction of commercial and recreational fisheries in both the Western and Eastern United States.

The unique physical characteristics of dam reservoirs lead to the creation of new harmful effects and the exacerbation of existing adverse environmental phenomena in the riverine system. One example of a new harm is the growth in the reservoir of algal blooms that did not naturally occur in the former riverine system.

All of these effects are attributable to some combination of flow control, thermal stratification, and sedimentation behind the dam.

FLOW: To meet electricity production or flood control needs, dam operators control the timing and amount of discharge from the reservoir to downstream waters. Low levels of released water result in a corresponding decrease in water depth and velocity downstream. Increasing flow would not only benefit downstream habitat, but could also increase dissolved oxygen levels by promoting turbulent mixing of downstream waters.

TEMPERATURE: Thermal stratification is when the reservoir contains a cold bottom layer and a much warmer top layer of water that do not mix…The unnatural temperature ranges in reservoirs, when compared to a natural stream or river, can also affect habitat in the reservoir and downstream. Releasing water from the colder hypolimnion layer can result in abnormally cold water discharged downstream. Sedimentation and thermal stratification contribute to hypoxia—dissolved oxygen levels that are too low to support complex aquatic life. Low dissolved oxygen levels are uncommon in natural riverine systems, mainly due to the increased air-water exchange linked to flow velocity, particularly in shallower rivers.

SEDIMENTATION: The dam-reservoir complex accumulates sediment from upstream, causing water quality problems not found in a natural river or natural lake system. Interruption of the natural sediment flow in the riverine system and release of sediment in dam discharge can cause problems for downstream habitat. 

On February 28, 2018, Global News released this clip. 

Peterborough Utilities Inc. looks to build two more hydropower stations along Trent-Severn Waterway

Hydropower dam proposed for Lock 31 in Buckhorn will look to harness the power of water. Peterborough Utilities Inc. (PUI) looks to build a 2.5-megawatt water power station at Lock 31. PUI is already operating four hydropower stations at three different locations along the river and is looking to expand its power generating capabilities north of the city. The generation station at Lock 31 will be the furthest power facility to the north of the city, while the utility group has plans to build another station at Lock 24 just between Lakefield and Peterborough.

These sites were identified as potential power sources by the Trent-Severn Waterway which is managed by Parks Canada.

“The actual use of the locks won’t be affected during the construction,” said Ernsting. “We’ll actually be on the dam side and so it won’t have any impact on the lock traffic.”

No impact on boat traffic… but what about the walleye fishery? Did the Trent-Severn Waterway give any thought to how harnessing the power of water for hydro would hurt the walleye fishery? Money comes first, ecology second!

2003: Fish Assemblage Changes in an Ozark River After Impoundment, Quinn and Kwak

Understanding how dramatic changes to the environment affect community structure is a major focus of aquatic ecology (Matthews 1998). The North American fish fauna has been subjected to a wide array of human-induced disturbances. Among the most widespread and drastic of disturbances has been the damming of rivers for hydroelectric power generation, flood control, recreational uses, and water storage…Our research documents a dramatic, long-term change in the riverine fish assemblage following dam construction and impoundment.

Changes in the thermal environment caused by hypolimnetic water releases downstream of the dam are likely a controlling factor, but other physical alterations, such as those related to the variation in flow associated with peaking hydropower generation, water chemistry (especially dissolved oxygen), the disruption of fish migration, and sediment and organic matter flow, may also be important.

Thus, the question remains as to the duration of monitoring that is sufficient to detect the effects of impoundment on the fish assemblage. The answer to this question certainly varies among ecosystems and should be addressed empirically with a monitoring program. Long-term monitoring programs using standardized fish sampling techniques should be planned at the earliest stages of major water development projects. Limiting the resources and requirements for monitoring may result in inappropriate management actions and inadequate mitigation for environmental losses.

Virtually every river in the 48 conterminous United States is now regulated in some way (Collier et al. 1996). Over 75,000 dams impound rivers in the United States; more are planned for the future, and many from the past are undergoing relicensing and review. The findings of our temporal comparison compel careful planning and deliberation in the development of the monitoring programs and ecological assessments associated with these projects.

Were any studies done prior to the hydraulic dams going in along the Trent-Severn Waterway System in the 1960s?

Were any studies done to predict how running water for hydro would hurt the fishery prior to the hydro stations slotted for installation in 2019?

Why wasn’t there a monitoring program that measured the harm done to aquatic life after the dams were installed?

Why is there no monitoring now?

This is not an isolated issue! Hydraulic dams harm ecosytems and cause decline to fish populations.

How is the Trent-Severn Waterway getting away with this sort of destruction?

Why doesn’t the MNRF start pointing fingers?

2002: Canada’s Recreational Fisheries: The Invisible Collapse?, Post

“Data from four high profile Canadian recreational fisheries show dramatic declines over the last several decades yet these declines have gone largely unnoticed by fishery scientists, managers, and the public.”

“We have seen that data on angler catch rates are not necessarily reflective of fish abundance until populations are near collapse. This lag between observed angler catch rates and fishery declines ensures management inaction until it is too late. We therefore require:

(1) fishery independent assessments of the status of fish populations, and

(2) changes in the management of recreational fishing that increase the visibility of fish population declines to agency biologists, the public, and politicians.

We must also recognize, quantify, and incorporate depensatory processes, where and when they exist, into dynamic management models to identify thresholds of population abundance that are necessary to sustain fish populations and the social and economic value that they provide. Only then can fisheries management, and society as a whole, hope to respond in a timely fashion to avoid the collapses and costly mistakes that have characterized the science and management of many of the world’s commercial fisheries.

This article was referenced by Cottage Life Magazine (Fall 2017) in its article titled, “Where did all the Fish Go?”


The invisible collapse is the sad tale of disappearing fisheries “not noticed” by fisheries scientists and managers until it’s too late.

In zone 17, the MNRF throws its hands up claiming “there’s no data,” but then doesn’t gather data (or accept volunteer data). The MNRF says “we put in a slot size!” but then doesn’t enforce poaching in a meaningful way. The MNRF says, “we can’t support fixing the spawning beds because that’s not our jurisdiction” but then puts no pressure on those who have jurisdiction, the Trent-Severn Waterway. 

The MNRF not only watched the collapse of our walleye fishery, it fought us in our efforts to do something. 

2002: Effects of Environmental Factors on Walleye Recruitment, Pitlo Jr.

“Environmental factors that occur before, during, and after spawning are important in governing the reproductive success of walleyes and saugers and ultimately affect year-class strength (Colby et al.) Discharge rates and sudden reductions in flow rates can affect year-class strength of river spawning walleyes[.] Other factors have been shown to affect survival of young walleyes and year-class abundance: water temperature during spawning and incubation [,] water levels during the spawning period [,] size of the spawning stock [,] food abundance [,] and storage ratio [.]

Additional mortality is caused by predation on walleye and sauger eggs and fry; attacks by fungus, slime bacterium, and bacterial disease (Colby et al. 1979); and in the upper Mississippi River, sheer, turbulence, and pressure changes caused by commercial navigation and hydropower development (Pitlo 1989).

On top of wildly fluctuating discharge rates, and pushing water from the bottom that is too cold, the pan fishery in the Kawartha Lakes has exploded.

According to the MNRF’s Science and Research Branch, Kawartha Lakes Fisheries Assessment Unit, 2016:

Pumpkinseed pan fish increased from 10,600 in 2001 to over 34,000 in 2012. That’s a 3x increase!

Bluegill increased from 58,406 in 2001 to 270,748 in 2012. A 4x increase!

At the same time, walleye decreased in numbers from 3.6 walleye in 2001 to 2.3 walleye in 2012.

For every 2 walleye in our lakes today, there are over 305 pan fish. Do we think walleye egg predation by pan fish is a serious issue in the continued decline of walleye? Yes! Of course it is. We need to stock some walleye to tip the balance back.

To read how important higher minumum water levels are to our ecosystem, read Larry Jones’ report: “Where did all the walleye go?” It’s a great read!



To read how important higher minimum water levels are to our ecosystem, read Larry Jones’ report: “Where did all the walleye go?” It’s a great read!