Big Water Walleyes
As winter finally begins to loosen its grip on North Dakota, anticipation for open water fishing on the Missouri River, south of Bismarck-Mandan, and the upper reaches of Devils Lake, grows for thousands of anglers.
And as sure as the eventual appearance of Canada geese above the North Dakota prairies, so too will come the questions/concerns expressed by some people regarding spring fishing regulations.
The North Dakota Game and Fish Department’s focus is to maintain the highest quality fisheries, while at the same time keeping fishing regulations as simple as possible.
Fishing across the state is arguably the best it’s ever been, and 99 percent of anglers who purchased a fishing license last year agree that the fishing regulations are easy to understand, according to recent surveys.
These surveys also indicated that North Dakota’s anglers are “satisfied,” to “very satisfied,” with the state’s fishing regulations.
However, most years a few anglers express an interest in having additional restrictions on walleye fishing in spring, which would have the intent of protecting female walleye during spawning.
This issue has generated discussion off and on since the early 1990s, when Game and Fish decided to expand the year-round open season for gamefish on the Missouri River System to all waters statewide.
Prior to that, the fishing season outside of the Missouri River System closed in mid-March and opened again in late April or early May, on the premise that northern pike and walleye would complete their respective spawning runs during this closed period.
This year-round season statewide has served North Dakota anglers well, while at the same time there is no fisheries survey data that suggests the open season has negatively influenced natural walleye reproduction on any water.
What follows is background information on current Game and Fish regulations, and the factors that could influence changes in those regulations in years to come.
Lake Oahe / Missouri River Walleye Fishery
More than 50,000 different anglers, with most targeting walleye, fish the Missouri River and Lake Oahe annually.
The Missouri River and Lake Oahe walleye fishery has for years provided outstanding opportunities to this diverse group, including fish for the fryer, trophies for the wall and countless memories.
Two things are inevitable every spring on the Missouri River and Lake Oahe in south central North Dakota. One, eager anglers will launch their boats at the first possible moment a river ramp is free of ice to search for walleye.
Two, Department fisheries biologists charged with managing this nationally renowned resource will field inquiries from a handful of anglers questioning whether more restrictive regulations, such as a closed season or fish size restrictions, primarily for walleye, would benefit the fishery.
To answer this, fisheries biologists routinely conduct netting and electrofishing surveys to monitor the health of the Missouri River fishery; assesses walleye age structure and growth rates; conduct creel surveys to gain an understanding of how anglers use the fishery; and periodically engage in special projects that provide additional information.
The current walleye tagging study, a cooperative project between North Dakota Game and Fish, South Dakota Game, Fish and Parks, and South Dakota State University, is one example.
Based on all this scientific information, fisheries biologists can analyze the Missouri River walleye population from two perspectives. First, would more restrictive regulations improve the biological health of the walleye population? And second, would more restrictive regulations increase the number of larger walleye available for anglers to (possibly) catch?
It is important to note that the Missouri River and Lake Oahe walleye fishery is maintained entirely through natural reproduction. North Dakota Game and Fish has not stocked walleye in its portion of the lake since 1981, and the last time South Dakota stocked walleye in its portion of Oahe was 1998.
Thus, maintaining an adequate number of sexually mature walleye, especially females, is a crucial consideration. It is also important to have an understanding of the species’ reproductive strategy in determining how many females are necessary for maintaining the fishery.
For example, Lake Oahe’s Beaver Bay is an important site for walleye reproduction. In spring 2016, the Department netted, tagged and released 758 mature female walleyes in Beaver Bay. Since a mature female walleye may carry 130,000 eggs, these 758 fish, in all likelihood, deposited close to 100 million eggs in the bay last spring.
Considering these 758 walleye represent only a small portion of fish in Beaver Bay, let alone all of the Missouri River and Lake Oahe, this population has the potential to produce many billions of offspring annually.
The amount of water Mother Nature provides, and how that water is managed by the U.S. Army Corps of Engineers, remains the primary factor governing the quality of this walleye fishery. Floods (1997 and 2011) and droughts (1988-92 and 2001-08) have periodically influenced this walleye fishery by reducing available habitat and causing forage shortages. Conversely, environmental conditions and water level management that favor forage fish production, walleye reproduction, growth and survival, have produced extraordinary results.
This is where the walleye’s reproductive strategy is clearly effective on the Missouri River and Lake Oahe. Walleye are capable of producing many more offspring than are needed so they can quickly increase in numbers when environmental conditions are favorable. Even if environmental conditions are poor, and the number of sexually mature walleyes declines, they still have the ability to rebound quickly. On some occasions, the Missouri River and Lake Oahe have seen walleye reproduction that was too good for the available forage base to support.
Another important biological consideration is maintaining a healthy length and age structure in this population. A healthy walleye population contains many more younger, smaller fish than large, older fish. However, the presence of large, older fish is a good indicator of a healthy population.
Game and Fish netting and electrofishing surveys indicate a balanced walleye population in the Missouri River and Lake Oahe. While small fish are abundant, fish 20 inches and longer are common, and fish living into their teens and measuring longer than 30 inches are sampled annually.
Would some form of length regulation or more restrictive harvest lead to anglers encountering, but not necessarily harvesting, larger walleye?
Game and Fish has used different length restrictions for walleye fisheries at times, including minimum length limits, maximum or “one-over” length limits, protected slot length limits (no harvest allowed on 15- to 20-inch fish, for example), and reverse slot length limits (harvest only allowed on 15- to 20-inch fish, for example).
After a half-century or more of experimenting with these various regulations on walleye fisheries across North America, biologists have pretty much defined the biological and social conditions that must be present for such regulations to yield positive results. Game and Fish biologists evaluate the utility of each of these regulation types annually to determine if they could help improve the present condition of any given fishery.
More anglers approach Game and Fish with questions regarding a one-over 20-inch length restriction than any other type of regulation. Again, the biological answer is that the Missouri River has plenty of mature female walleyes to maintain this naturally reproducing population. But from a social perspective, would a one-over 20-inch length restriction enable anglers to catch more big fish?
A Game and Fish Department creel survey of Missouri River and Lake Oahe anglers in 2015 provides some insight as to how a one-over 20-inch regulation would influence angler use of these fish.
Creel clerks interviewed 1,126 individual anglers (498 fishing parties) between Garrison Dam and the South Dakota border, and measured the lengths of walleye harvested by anglers whenever possible. Sixty five percent of harvested walleye were between 15 and 20 inches, 34 percent were under 15 inches, and less than 1 percent were 20 inches or longer.
None of the parties interviewed had more than one walleye 20 inches or longer per angler. Thus, a one-over 20-inch regulation would not have prevented the harvest of a single walleye 20 inches or longer among the 1,126 anglers surveyed.
Creel clerks clearly did not interview every single angler who fished the Missouri River or Lake Oahe in 2015. However, the survey information does provide overwhelming confidence that a one-over 20-inch regulation would have virtually no impact on this walleye fishery.
Currently, the five-walleye daily limit, with no length restrictions, is maintaining a biologically healthy walleye population in the Missouri River and Lake Oahe. More restrictive harvest regulations at this time are biologically unnecessary, and would not likely lead anglers to catch more large walleye. Needlessly complicating regulations, without benefiting the fishery or anglers, is not the North Dakota Game and Fish Department’s philosophy.
However, that doesn’t mean the current situation will last forever, and Game and Fish biologists will continue to monitor and study this walleye population, and the anglers who use it, to ensure that effective harvest regulations are in place for maintaining the highest quality fishing possible for years to come.
Devils Lake and Its Upper Basin
Spring fishing is popular in the Devils Lake region because it gives shore-anglers their best opportunity of the year to catch a large walleye.
Although the good fishing usually only lasts a few weeks, Devils Lake region anglers often express concern that too many large walleye, fish longer than 20 inches, are harvested during this time, which will lead to poor walleye reproduction.
Biologists monitor the Devils Lake walleye population annually to determine if any conditions exist that would warrant a special regulation, such as a maximum length limit, or the commonly requested one-over limit.
The first thing to look at is if the lake has enough female walleyes to carry out a successful reproduction effort.
Spring fishing in the upper Devils Lake basin was very good from 2009-13, with the exception of 2012. In spite of this harvest, three of the four largest year-classes ever were produced since 2008, with the largest ever documented at Devils Lake in 2009.
Additionally, in 2012 the percentage of walleye longer than 15 inches was well below average, yet the second largest year-class ever was produced that year. This is pretty good evidence that the spring walleye harvest has not limited reproduction, and Devils Lake continues to maintain ample brood stock to produce good year-classes when conditions are favorable.
When evaluating whether a new harvest restriction is appropriate, biologists look for some evidence that harvest is actually having a negative effect on the population.
At Devils Lake, the total walleye mortality rate, which includes harvest and natural mortality, has in recent years been below what biologists across North America consider the normal range of about 40-55 percent.
Additionally, creel surveys indicate that anglers harvest large walleye at a lower rate than smaller fish. For example, test netting in 2013 showed that walleye longer than 20 inches made up more than 9 percent of the Devils lake walleye population. However, during a creel survey that summer, only about 3 percent of the fish that anglers caught and kept were longer than 20 inches, indicating that either these large walleye were harder to catch, or perhaps anglers were more likely to release them.
With all this scientific research and angler activity surveys to draw on, Game and Fish biologists are confident that the Devils Lake basin walleye population does not meet the biological criteria that would warrant a maximum length type limit to protect fish for spawning.
In addition, the Game and Fish Department also considers whether further regulation could provide some social benefit, such as increasing the amount of larger walleyes for anglers to catch. Creel surveys in the Devils Lake region over the years provide some insight into whether regulation changes might have generated positive results.
During summer 2013, when only 3 percent of harvested walleye were longer than 20 inches, a one-over 20-inch limit would have required anglers to release 1,345 walleyes out of the total harvest of about 383,000 fish.
While that sounds like a lot of fish, tagging studies at Devils Lake have shown that only 9 percent of tagged walleye were ever caught again after their first release. That means about 121 of those large walleye in 2013 may have been caught again.
Looking at it a different way, if a regulation had required the release of 1,345 walleye that summer, anglers would probably not catch 1,224 of those fish again, meaning they would likely die of natural causes.
This would create a scenario where a lot of large walleyes would be wasted in an effort to enhance the fishing experience of a limited few. Game and Fish does not believe it is worth restricting anglers who are lucky or skilled enough to catch those large fish the first time, even if they choose to keep more than one per day.
Department fisheries biologists also measured walleyes harvested in May of 2013 from the coulees that flow into the Lake Irvine and Lake Alice complex, which eventually empties into Devils Lake. This survey found that about 59 percent of the harvested walleye were 20 inches or longer, and that a one-over 20-inch regulation would have required the release of about half of those fish.
Because fewer fish overall were harvested in spring, released fish would have numbered in the hundreds, instead of the thousands observed during the summer survey on Devils Lake. Most of these hundreds of fish would have returned to Lake Irvine or Lake Alice, where they would have found refuge due to difficult summer access to Lake Irvine, and no summer fishing allowed on Lake Alice.
Considering the vast expanse of water in the upper Devils Lake basin, the only time many of these fish are vulnerable to anglers is for a short time in spring.
A more serious threat to the walleye (and other fish) population in the upper portions of the Devils Lake system is a decrease in water levels. These upper basin lakes are relatively shallow and declining water levels could eventually lead to serious winterkill.
Game and Fish assessment of current conditions at Devils Lake indicates that there is really no biological or social benefit to gain from restricting harvest of large walleye in the Devils Lake region. Any new maximum length or one-over regulation would needlessly restrict angler opportunities, and would not benefit the walleye population or anglers.
However, as with the Missouri River System, if conditions change, Game and Fish is committed to establishing new regulations if there is a reasonable likelihood of protecting the fishery for biological reasons, or enhancing fishing experiences.
Fueled by Natural Reproduction
By Greg Power
The Missouri River/Lake Oahe is one water body in North Dakota that has a walleye population fully supported by natural reproduction. Since this valuable fishery developed in the 1970s, strong year-classes of naturally reproduced walleye have occurred at regular 4-6 year intervals (1978, 1982, 1986, 1995, 2001, and 2009, for example). Due to drought conditions, there was little water in Lake Oahe between 1989-93 and 2002-07.
These strong year-classes dominate the fishery for 4-8 years thereafter and have historically provided angler catch rates far higher than noted at most other walleye fisheries across the country.
On the surface, knowing that Lake Oahe regularly produces more than enough walleye to support a great fishery is wonderful news. However, other than a lack of water during drought conditions, the largest issue that has faced this fishery in the past 40 years is too many walleye during times of poor forage populations.
In a good year, young-of-the-year white bass, yellow perch, crappie and some minnow species are abundant and provide needed groceries for the walleye population. In addition, during years of warmer than normal winters, gizzard shad can also be abundant and are an excellent forage source.
Yet, there are years when there simply isn’t enough forage to support the strong predator base, which also includes northern pike and channel catfish. And if one bad year of forage production is followed by another, the condition of the walleye fishery declines dramatically, as fish become skinny and basically quit growing. If forage problems persist, the overall walleye population dwindles rapidly due to high natural mortality.
Anglers who fished Lake Oahe/Missouri River from 2003-08 observed an unhealthy fishery, with numerous skinny fish. The cause was too many walleye and not enough forage. The 2001 walleye year-class was strong, but years of low lake levels, with poor forage production, followed. As a result, these fish essentially quit growing. For example, a 14-inch, 4-year-old walleye caught in 2005 was typically still just 14 inches in 2007.
In 2009, higher water levels returned to Lake Oahe/Missouri River and so did the forage. For those 2001 year-class walleye that did survive the lean years of little food, there was an immediate and positive response demonstrated by a remarkable growth spurt. Walleye again grew, resulting in many happy anglers.
Over the past 40-plus years, most of the time Lake Oahe and the Missouri River has supported a healthy walleye harvest. Only on a couple of occasions did biologists feel additional size restriction regulations were needed. When these regulations were no longer needed, they were removed.
Too Many Walleye?
By Greg Power
The North Dakota Game and Fish Department’s approach to walleye management across the state over the years has served anglers well.
A strong stocking program, developing and maintaining access, and consistent, straightforward regulations have helped produce an annual statewide harvest of 1-2 million walleye, while providing needed protection to ensure strong populations year-after-year.
In nearly all North Dakota water bodies, periodic stocking is needed to maintain walleye populations, as natural reproduction is generally not sufficient. What typically limits natural reproduction is the lack of good walleye spawning substrate, high salinity levels in many lakes, and water level fluctuations usually caused by strong winds during the egg incubation period.
Since 1999, fisheries managers have transformed more than 60 prairie wetlands into new walleye lakes, totaling 65,000 acres. With few exceptions, these lakes are the result of stocking decisions based simply on the balance of predator (walleye) and prey (mainly fathead minnows).
Department fisheries managers closely monitor fathead minnow abundance through netting surveys. When minnow numbers are high, walleye stocking rates are increased, and when minnow numbers are low, walleye stocking rates are decreased.
It’s all about the groceries in the lake.
When a given lake has a high fathead minnow population, anglers sometimes believe the walleye are “fished out” because they are not easily caught. In reality, when there’s simply a lot of easy meals for existing predators, it’s more difficult for anglers to compete with all the free groceries.
The upside of maintaining a lake by stocking walleye is that fisheries managers can change stocking rates based on forage conditions. The goal is to maintain a strong walleye population that is just hungry enough to provide a good bite for eager anglers.
The new prairie walleye lake phenomenon over the last 20-plus years has given fisheries managers a chance to study walleye and forage populations in relation to angler success. Over time, these observations have produced a “recipe” for management that is working well for anglers and biologists alike.
Even on the big waters of Lake Sakakawea and Devils Lake, the decision of whether to stock walleye and how many is based on the strength of the respective forage bases. Fortunately, current forage conditions are excellent in Sakakawea (rainbow smelt) and good in Devils Lake (yellow perch, white bass and freshwater shrimp), and both waters are being stocked annually to supplement natural reproduction.
As a general rule, walleye and most predator fish grow well in North Dakota when forage allows. However, appropriate management is never static, and finding that right balance between predator and prey is sometimes challenging.
Water levels in North Dakota lakes, especially reservoirs, fluctuate dramatically between years, and often within a year. The difference in Lake Sakakawea over time, for example, is nearly 50 feet, while Jamestown and Pipestem reservoirs can fluctuate up to 20 to 40 feet per year. Our weather is extreme and the wind constant. Snowpack on lakes can vary from almost none to a few feet, sometimes leading to winterkill.
Yes, there are places and times when a North Dakota water could have too many walleyes, resulting in a suppressed forage base. The pendulum, however, can swing rapidly, and water bodies that were suffering from too few groceries can rebound dramatically, meaning that stunted fish growth can move toward rapid growth when forage conditions improve.
North Dakota fishing lakes will continue to be monitored for negative impacts caused by overexploitation. However, Department fisheries biologists generally support angler walleye harvest when a good bite is ongoing in a given lake. To a large extent, these fish cannot be stockpiled due to common and dramatic shifts in forage base.
If anglers don’t harvest these fish, Mother Nature will eliminate them. That’s just the harsh reality of survival on the Northern Plains. A walleye in the frying pan is preferred to a dead fish on the bottom of the lake.
On the whole, the past decade has offered the best walleye fishing ever in North Dakota. And Department fisheries biologists will continue to tweak walleye stocking recipes to ensure a bright future.