June 1, 2020

Understanding the Walleye Spawn

To many walleye anglers, the spawn is one of the most discussed, but often misunderstood topics there is in fishing. The walleye spawn can generate a variety of discussions. While many of us are familiar with the discussion regarding the argument for an open or closed walleye season, other conversations include the importance of fish stocking, why spring fishing is so good and knowing that our favorite fishery will have walleye for years to come. Today, we are going to break down the biological factors in play regarding walleye spawning and survival.

Importance of the Spawn

This may seem like an open and shut case. The walleye spawn is important because it gives us more fish to catch. Correct, walleye spawn is critical because it is how walleye naturally reproduce and put new fish in the system. However, it is not that simple. When evaluating a fishery, biologists are looking for three key factors: recruitment, growth and mortality. Let’s take a look at how these all play into a walleye’s life.

Recruitment is the first step. Recruitment means a fish has entered the population. This is where the spawn comes into play. to understand recruitment, let’s look at this situation as a college sports program. When we discuss recruiting, we are looking at potential players we would like to have on our team. These potential players are the eggs and fry. They exist, but they are not on our team yet. 

Let’s say that we have 100 possible players we are looking to recruit. These recruits are the eggs. Of these 100 players, 50 decide they ultimately want to play at the college level. Now they’re our fry. They have hatched and are navigating the waters as a vulnerable prey source for any fish that may want to eat them. Of these 50 players, 20 of them have decided they want to do something other than sports and 20 of them have been signed with other teams. This means they have either been lost due to an unforeseen circumstance, let’s call it a weather event, or been “eaten” by other teams. This leaves us with 10 players for our team out of the original 100. We have successfully recruited these players to our team, or in this case fish into our population.

Once we have these fish recruited, growth becomes the next important factor. Growth is determined by forage availability. If there is plenty of forage in the system, growth rates will be strong. However, if there is not adequate forage for the amount of fish in the system, growth rates will be poor. Growth is critical, because it is necessary for walleye to reach desired sizes for anglers. On a biological front, growth also allows walleyes to reach sexual maturity and begin devoting calories to gonad development, in particular eggs.

To go back to our college sports team example, growth is equivalent to development as a player. Successful teams are going to take incoming recruits and implement training and nutrition programs, practices and ultimately competition. These factors will be what “feed” a recruit and allow them to grow into a more successful athlete. Successful athletes will foster successful teams. 

The final factor is mortality. This is difficult to pinpoint, because it can factor into a walleye’s life at any point. Once a fish has been recruited into the system, it is susceptible to mortality at all times. This mortality may come in the form of being prey for a larger fish or animal, winter or summerkill, angler harvest or just old age. It is important to note that once a fish has suffered mortality, it has been removed from the population for good. This could be over the winter, spring, summer or fall-all mortality is mortality.

Let’s complete the example above, but try not to be too grim in the process. For our example, let’s look at mortality as an athlete that could suffer a career-ending injury, transfers to another program (is eaten by that program) or simply graduates or decides they do not wish to continue their college sports career. 

Now where would stocking come in the process? Stocking efforts are an attempt to supplement natural recruitment. If a waterbody would not be able to produce the amount of fish to reach desired management levels, it is often supplemented with stocking efforts. These stocking efforts play into recruitment, imagine it as a kick-start to the first chain we discussed above. However, for the rest of the article let’s stick with discussing natural reproduction.

Spawning Factors

There are two major factors that play into the timing of spawning: photoperiod and water temperature. Water temperature is easy to understand, but photoperiod is slightly more complex. Photoperiod is simply how long the day is. This will never change, year in and year out. Photoperiod has been known to impact the timing of migration, reproduction and on smaller scales feeding and resting times. Many people say “fish don’t know the calendar”, but this is not true. Photoperiod can be considered the calendar of the natural world.

Now, as we all know, the weather does not play by the rules of photoperiod. Some years may produce an early spring, while other years could have snowstorms continuing into April and May across the Midwest. This is when the second factor comes into play, water temperature. 

There are numerous variables that can impact water temperature: air temperature, precipitation, water levels, water turbidity, wind direction and speed, amount of flow and numerous other factors can impact water temperature daily, if not hourly. There is no “one-size-fits-all” for water temperatures, however: you can expect spawning activity to begin when water begins reaching 40 degrees Fahrenheit, peaking at approximately 44-48 degrees. You may also observe spawning activity taking place with water temperatures in the low 50s. This is where the package comes together.

To put this all together, let’s take a look at a lake I observed spawning activity on for three years. This lake is a large, clear, fishbowl lake in eastern South Dakota that can reach depths of approximately 30 feet.

In 2015, ice-out occurred in mid-late March and was followed by unseasonably warm temperatures. I observed fish moving into the spawning area on April 1, with peak spawning activity taking place from April 7-April 16. 

In 2016, ice-out occurred at roughly the same time in March, but the following weather patterns were cooler and more unstable. Because of the weather patterns, I did not observe fish moving into the spawning area until April 13. This year the process was in higher gear and I observed peak spawning activity taking place from April 17-April 25. While spawning duration was roughly the same length, it was pushed back approximately 10 days because the water temperatures and weather patterns were less ideal.

In 2017, ice-out was slightly delayed, but still near the end of March. The weather patterns were then slightly warmer than 2016 and closer to 2015 conditions. I observed fish moving into the spawning area on April 8, but what was different about this year was the water was significantly dirtier and there was unstable weather patterns throughout this time. This led to an observation of peak spawning activity taking place in a shorter window, roughly April 11-April 15.

In 2018, ice-out was so delayed that even at the end of April ice was still not off the lake. Because of this, I unfortunately had graduated from South Dakota State University and moved to Chamberlain, SD and was unable to observe how this impacted spawning timing. 

The above case study showed that the spawning window was roughly April 7-April 25, but weather conditions can vary that from a few days to a few weeks, depending on how severe the weather conditions are. It is important to note this is for a specific lake, even over a small geographic area different lakes may enter the spawning stage during different times. As you move further north or south, this timing can be even more altered. There is no replacement to time spent on the water making observations, but understanding how location, waterbody characteristics, photoperiod and weather patterns can impact the timing of spawn is an excellent starting point.

Spawning Locations

Now that we have determined when we should expect walleye to begin moving towards spawning locations, it is important to note where these spawning locations are. We have discussed that the various characteristics of waterbodies can impact the timing of spawn, but it can also impact location. Let’s take a look at three major types of waterbodies we can expect to find walleyes in.

A reservoir is a man-made waterbody, often by damming a river or tributary. The Missouri River reservoirs are an excellent example. Many of the country’s top walleye fisheries are reservoirs. These include Lake Sakakawea, Lake Oahe, Lake Sharpe and Lake Francis Case across the Dakotas, Lake McConaughy in Nebraska and the Columbia River in the northwest United States.

Reservoir fish will move into the upper third of a reservoir to spawn. This stretch of a reservoir often has the greatest characteristics of a river. It is important to note that walleyes are by nature a river species and current can keep oxygen coming across their eggs as well as prevent silt and sediment build-up. The lower third of a reservoir often has more characteristics of a lake and fish will often move downstream after spawning to spend summer in the deeper, cooler waters.

The second type of fishery we will look at is a lake that has a river or other tributary available to the fish to access without being blocked by a dam. If one of these areas is available, walleye may migrate miles upon miles to reach this specific area. The third type of fishery is a similar lake, but one that does not have a river or tributary available. In this situation, walleye will seek spawning structure and rely on wind to keep oxygen coming across their eggs.

Regardless what type of waterbody you are discussing, the specific spawning location remains the same. Walleye will seek out rock, gravel or other hard substrates to disperse their eggs. Generally these areas are quite shallow, sometimes as shallow as one foot, but they could also be as deep as 10 feet. If you can find these types of areas, the next step to analyze is how adjacent they are to deep water. While male walleye will often cruise the spawning areas for a prolonged period of time, females will stage in deep water until they are ready to spawn. The deep water is also important for all fish, should they need to escape to safety from adverse weather conditions. 

The final factor to consider in walleye spawning location is that as discussed above, there is not a certain period of time spawning will take place. Specific areas of a waterbody warm at different speeds and depending on the size of the waterbody, it is very possible there are fish in pre-spawn, spawn and post-spawn stages all at the same time. The same can be said for lakes, as a lake in one area may be nearing the completion of spawn, where another lake may still be in the pre-spawn stages. 

The moral of this story is if your fish you have been observing have changed their stage and pattern, a quick boat or truck ride may have you on a pod of fish in a different stage. Additionally, fish may filter on to a specific area in waves as they reach different stages of spawn. Don’t be afraid to check back in a day or two and see if more fish have moved onto a spawning structure. 

Wrapping It Up

The walleye spawn is one of the hottest topics among anglers every spring. While the vast majority of these discussions revolve around social issues such as an open or closed walleye season or selective harvest, there is no arguing the biological factors that relate to the spawn. Today we analyzed the life cycle of a walleye, the factors related to spawning and the locations they choose to spawn. If you’ve made it this far, I commend you. Understanding the species we pursue and what makes a sustainable fishery is obviously very important to you. You are exactly the type of angler who will help keep our sport strong for years to come. Good fishing!

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