NORTH DAKOTA OUTDOORS MAGAZINE

Lengthy Look at the Big 3

Paul Bailey, Todd Caspers, Russ Kinzler and Scott Gangl

Fishing regulations are important tools that biologists can use to limit harvest to maintain the health and quality of fish populations. At the North Dakota Game and Fish Department, our philosophy is to keep fishing regulations as simple and consistent as possible for anglers by only implementing regulations that will provide a benefit to fish populations or anglers.

Length limits are designed to restrict harvest of certain sizes of fish, and come in three basic types: 1) minimum length limits prohibit harvest of fish under a specific size, 2) maximum length, or “one-over” limits restrict harvest of large fish, and 3) slot limits restrict harvest on a specific size-range of fish.

To properly assess the need for length limits, biologists examine the primary population functions that shape fish populations: reproduction or recruitment (the rate at which fish are added to a population), growth (the rate at which fish are increasing in size) and mortality (the rate at which fish are leaving a population). Would a regulation increase recruitment by protecting spawning-size fish? Are small fish abundant, or do they need protection from harvest until they reach harvestable size? Would protecting small fish result in stunting if those fish are growing slowly? Is angling harvest negatively impacting the quality of fishing or health of the fishery? Would a length limit ultimately improve fishing by increasing the numbers or size of fish caught by anglers?

These questions, and more, are considered by biologists tasked with managing the state’s fisheries. When the criteria for an effective regulation are met, it may be proposed for implemening as a new regulation. But implementing a regulation that doesn’t meet specific criteria for success may be ineffective or outright harmful to the fish population.

Referred to colloquially as the Big 3 walleye fisheries, Devils Lake, Lake Sakakawea, and the Missouri River and Lake Oahe below Garrison Dam, are the most intensively managed walleye fisheries in North Dakota. Due to their importance as angling destinations, both locally and nationally, our biologists review their data every year to determine if a length limit regulation is necessary to protect or improve walleye fishing on the Big 3. On the following pages, biologists breakdown their length limit evaluations for 2025 data.

Missouri River and Lake Oahe

Seeing good recruitment of new fish into a population is most often a welcome event by both fisheries biologists and anglers as it signals that fish should be abundant for years to come. This is especially true for the walleye population in the Missouri River and North Dakota portion of Lake Oahe where the Department relies on natural reproduction to maintain this fishery. However, excellent walleye recruitment over the last dozen or so years exemplifies too much of a good thing.

The good news regarding this excellent recruitment is that it indicates that there are plenty of mature female walleye to maintain this population, which is certainly welcome news as we can then devote our hatchery resources elsewhere.

The other side of this double-edged sword is that small walleye have been extremely abundant and taxed the available forage. This has resulted in Missouri River and Lake Oahe walleye generally being in poor condition and exhibiting slow growth. For example, walleye in many of our state’s fisheries reach 15 inches at 3 years of age. However, walleye in the Missouri River and Lake Oahe are currently taking 5 or 6 years to reach this benchmark.

North Dakota anglers can generally harvest up to one-third or so of the walleye from a fishery without jeopardizing the sustainability of that population. The Department collaborated with South Dakota Game, Fish and Parks in 2025 to estimate walleye angling mortality between Garrison and Oahe dams and found that anglers harvested approximately 17% of the walleye in the North Dakota portion of this fishery. This indicates that walleye angling mortality is acceptably low.

Collectively, this indicates that the Missouri River and Lake Oahe walleye fishery is currently characterized by excellent recruitment, slow growth, and low walleye angling mortality. This information then allows us to assess the potential benefits (or detriments) of various length limits.

Applying a minimum length limit (15 inches for example) would likely be detrimental to this fish population. Excellent recruitment and slow growth have led to an abundance of small walleye and restricting harvest of these small fish would likely exacerbate these issues. In fact, the Department has encouraged anglers to “not feel bad” about harvesting the 12- to 15-inch fish they encounter as, under the present conditions, may benefit this fish population by reducing the abundance of small fish, providing more forage for those that remain, and improving growth rates.

Considering the opposite end of the spectrum, would a maximum (or one-over) length limit benefit this fishery in some way? That answer is a clear no from a recruitment perspective as there is no indication that the reproductive potential of walleye in this fishery is in any way limited by the abundance of mature female fish. Information from the most recent creel survey (2024) also indicates that anglers seldom harvest more than one walleye over 20 inches per trip. Rather, most angler harvest is focused on walleyes between 13-20 inches and anglers elect to release many of the larger walleye that they catch. Thus, applying a maximum (or one-over) would likely not reduce the harvest of large walleye.

That brings us to slot length limits. The first type to consider is a protected slot whereby fish of a certain size range, say 15-20 inches, would be protected from harvest. The current low rate of walleye angling mortality indicates that this type of regulation is unnecessary. Additionally, such a regulation is likely to be enormously unpopular with anglers as these are the sizes of fish that many prefer to harvest.

Zach Kjos, Department fisheries biologist, with a Lake Sakakawea walleye.

The other type of slot length limit to consider is a harvest slot, whereby the harvest of fish both below and above a certain size range would be restricted. For example, harvest would only be allowed on fish from 15-20 inches. Thus, a harvest slot is really a combination of both a minimum and maximum length limit and (as described earlier) neither is currently warranted for this fishery. (Furthermore, results from recent tagging studies and creel surveys indicate that many North Dakota walleye anglers voluntarily adhere to a self-imposed slot limit by focusing their harvest on “eater-sized” fish while releasing the small and large fish they catch.)

This routine analysis of recruitment, growth and mortality of Missouri River and Lake Oahe walleye indicates that this fishery is unlikely to benefit from a more restrictive length limit. Understanding this, the Department prefers to give individual anglers the freedom to make their own decisions on the sizes of walleye they choose to harvest within our five fish daily limit.

Devils Lake

Currently, the Devils Lake walleye population does not meet some of the criteria necessary to benefit from a minimum length limit. In Devils Lake, walleye recruitment is typically good and young walleye are usually abundant, so protecting them isn’t necessary. There are usually good numbers of 12- to 15-inch walleye in the lake, and a minimum length limit would needlessly restrict harvest opportunities for anglers and could decrease growth due to increased competition between small fish if they were protected by a minimum size limit.

Angler harvest of young fish also isn’t a problem, as total mortality (which is due to harvest as well as natural causes) for the population is lower than what is considered normal. In general, Devils Lake walleye will grow from about 13 inches at age 3 to 15 inches at age 4, so it only takes them about 1 year to grow from being a “small keeper” to a “quality keeper.” This means that the smaller fish are usually only susceptible to harvest for about 1 year before they become quality-sized fish, and most of them can grow into quality-sized fish without being protected.

Devils Lake’s walleye population does not meet the criteria necessary to see a benefit from some type of maximum length limit. Large walleye hatches in the high-water era indicate that current regulations are maintaining sufficient numbers of adults in the lake for successful spawning. In fact, seven of the eight largest hatches have been produced since 2008. In the past 10 years, all years produced reproduction events ranging from fair to excellent. The largest hatch ever produced occurred in 2025. There are adequate numbers of adults in the lake to reproduce successfully. Moreover, there have been times when there have been so many small walleye in the lake that their growth rates have slowed down.

Many anglers release large walleye voluntarily as well. We see evidence of this in our creel surveys as well as in tagging data. For example, for walleye that were tagged in Devils Lake in 2025, so far about 95% of the fish that were 13-20 inches when tagged were harvested if caught. This harvest probability dropped to 78% for fish that were 20-22 inches when tagged, 66% for fish that were 22-24 inches when tagged, and 32% for fish that were longer than 24 inches when tagged. Basically, walleye over 20 inches will be released more often than fish less than 20 inches, and the likelihood of getting released increases as length increases.

Since the Devils Lake walleye population does not meet the criteria for either a minimum or a maximum length limit, a harvest slot limit would not be appropriate either. Also, when considering a protected slot, there are a couple of necessary criteria lacking for this type of regulation to be successful at Devils Lake. The criteria not being met to see success from this type of length limit is that small fish need to have slow growth and high mortality. Small walleye in Devils Lake have adequate growth and their mortality rate isn’t particularly high. This type of regulation would work well in a situation where it’s necessary to protect moderate-sized fish while forcing anglers to mostly harvest abundant, small, slow-growing fish that are likely to die of natural causes anyway. Those conditions don’t exist on Devils Lake. The small fish can grow into the moderate-size group on their own, so forcing anglers to harvest these small fish wouldn’t be wise. Additionally, it is the moderate-sized walleye in Devils Lake that display slower growth, so protecting all of those fish from harvest may lead to a further reduction in their growth rates.

Another potential use of a protected slot limit could be to save larger fish (20- to 26-inch walleye for example) for the purposes of having more large females available to spawn. However, as previously discussed, Devils Lake walleye already exhibit the ability to reproduce successfully, so this use of a protected slot limit isn’t necessary.

We have seen that the current walleye population of Devils Lake is not really suited to any type of length limit. However, the North Dakota Game and Fish Department will continue to monitor the fishery, and if conditions change, we will consider whatever regulation is deemed necessary to protect this valuable resource.

Lake Sakakawea

Lake Sakakawea is approximately 178 miles long and covers 382,000 surface acres when full. Due to Sakakawea’s size, we often divide the lake when looking at data. Reproduction is very different from the upper portion (west end) compared to the lower portion (east end). The west end is shallower and warms up quicker in spring and we do see some natural reproduction in this part of the lake, whereas the east end is much colder and deeper with little to no natural reproduction. The lack of reproduction on the lower end is not limited by the number of adult walleye but likely due to the colder temperature that can impact egg survival and limit food for newly hatched fry.

On Lake Sakakawea, stocking of fingerlings has been used to supplement natural reproduction or the lack of natural reproduction in the middle and lower portions of the lake. A natural spawn or stocking is generally considered successful once enough of the young fish have survived and have been recruited to the adult population. At least some reproduction has been documented every year dating back to 1972 on Lake Sakakawea and more than half of the top 12 year-classes have been documented in the past 12 years.

Walleye growth on Lake Sakakawea can vary with slower growth during drought periods and good growth under normal and high lake elevations. Currently, walleye growth is considered good as they usually reach 14 inches by age 3 and 16 inches by their fourth year.

Walleye on Lake Sakakawea can live a very long time with fish up to 20 years old being documented most years. The oldest walleye documented during annual sampling was a 27-year-old fish sampled in 2018. Total annual mortality for walleye ages 3 to 15 was estimated at 35% in 2025 and is considered acceptable for maintaining the long-term sustainability of the population. Angler exploitation on Lake Sakakawea ranged from 14% to 22% during a 2019 to 2022 tagging study indicating angling mortality was low. This study also indicated walleye were more likely to die from natural causes than harvest from anglers.

Would some sort of length limit benefit Lake Sakakawea?

Lake Sakakawea has had a 14-inch minimum length limit in the past, but it currently is not needed. The lake has good reproductive success due to a combination of natural reproduction and stocking when needed. Walleye growth is good and angling mortality is low, especially on small fish. A creel survey conducted in 2024 indicated that walleye anglers do no tend to keep fish under 14 inches. Creel clerks measured 7,230 walleyes during the survey and only 334 (4.6%) were less than 14 inches.

Would Lake Sakakawea benefit from a maximum or one-over length Limit?

Recruitment on the upper portion of the lake is generally good. Recruitment in the middle and lower portions is generally limited in years when fish are not stocked and when needed, stocking has proven to be successful in augmenting the population. The poor recruitment in non-stock years is due to environmental conditions and not low numbers of large, mature fish.

A one-over 20 inches regulation is often suggested by anglers as a regulation that would benefit Lake Sakakawea. Yet both creel surveys in 2021 and 2024 showed that such a regulation would not impact the fishery. In 2021, only 4% of individual anglers harvested more than one walleye over 20 inches and only 1.8% of angler parties who had their limits of fish measured harvested more walleye over 20 inches than the number of anglers in their party. During the 2024 creel survey, 9% of individual anglers harvested more than one walleye over 20 inches and 2.9% of angler parties who had their limits of fish measured harvested more walleye over 20 inches than the number of anglers in their party. In 2021, fish over 20 inches accounted for 4% of the total harvest and in 2024, fish over 20 inches accounted for 7% of the total harvest. Currently, a maximum or one-over limit would not significantly reduce the harvest of large walleye

Finally, let’s consider slot limits. The most likely slot limits for Lake Sakakawea would be either 14-20 inches or a 15- to 20-inch harvest slot. This is what anglers on Lake Sakakawea are already doing. Data from the last two creel surveys showed that 82% of the walleye harvested in 2021 and 86% of the walleye harvested in 2024 were 14-20 inches. In 2021, 64% of the walleye harvested were 15 to 20 inches and in 2024, 81.5% of the fish harvested were from 15 to 20 inches. A harvest slot, is not necessary but is basically what most anglers are already voluntarily doing.

Considering a protected slot — such as the eater-sized fish Sakakawea anglers harvest — current angling mortality does indicate this is needed but would likely be very unpopular with anglers.

The Lake Sakakawea walleye population is monitored yearly and the information we have gathered on reproduction, recruitment, growth, and mortality indicate the current walleye fishery would not benefit from any type of length limit.

Return to North Dakota Outdoors May 2026 Edition