As the Earth, moon and other celestial bodies revolve around the sun, a natural rhythm of seasonal change is produced. The 23½-degree tilt of the Earth’s axis on its elliptical orbit results in predictable spring and autumn equinoxes, and summer and winter solstices, which are distinct, annual celestial events.
While the dates of these events are stable and predictable, local weather patterns can nevertheless be erratic, with one spring season being unusually warm, perhaps followed by one or more springs that are abnormally cold or variable. A summer can be long, short or of average duration, depending on a complex interaction of environmental factors. And to complicate matters further, the farther north or south you move from the equator, the more varied the seasons and weather patterns become.
As a result, manmade clocks and calendars can only approximate the arrival, pace or “feel” of a season, and are little more than general guidelines than precise indicators of seasonal fish behavior. For fish, seasons do not automatically arrive on the same dates each year. Rather, worldwide and local weather patterns dramatically affect the arrival and duration of seasons, directly influencing localized water temperatures in the process.
From a pure angling perspective, a person does not need to know precisely why seasons fluctuate like this. It’s only important that you realize they do, and that you react accordingly— because bass and other gamefish most certainly do!
Changes In Latitude, Attitude As anglers, we need to look at the seasons from a much broader perspective, much like a bass would view them. The reason is obvious: Seasons also arrive by latitude, not just according to the calendar. For example: At the extreme limits of the U.S. largemouth bass range, spawning season arrives at southern Florida’s Lake Okeechobee sometime in February— many months before it arrives on Lake of the Woods on the Minnesota/ Ontario border. The spawn period in the Deep South lasts several months, slowly building to a peak before eventually tapering off.
In comparison, bass in Lake of the Woods typically can’t begin spawning until sometime in June, after the ice goes off the lake and the water begins warming to suitable levels. Faced with such a late spring warm-up, the spawn period for far-northern bass is typically compressed into a relatively short window lasting a few weeks to a month, followed by rapidly warming water as summer arrives in earnest.
In Southern waters, some groups of bass may have the opportunity to spawn several times during their extended season, ensuring a good spawn despite periods of unstable weather. In Northern waters, however, it’s generally a one-shot, all-or-nothing deal, subject to the negative effects of severe cold fronts that might reduce spawning success. Should a poor spawn occur, there’s no backup.
When we examine the bigger picture— the entire year, not simply the spawning period—we find that bass location and activity are primarily driven by two natural phenomena: Changing environmental conditions associated with changing water temperatures; and the position of the Earth’s orbit in relation to the Sun, which affects the day length and light intensity.
Water temperature in itself is much more of an indicator than it is a determining factor; it is merely the simplest way for anglers to gauge the complex and ever-changing relationship between seasonal fish locations, forage levels, aquatic plant growth and other environmental factors.
It takes into account the latitude where bass live, and helps predict a sequence of events in the lives of bass: spawning, moving to summer habitat, shifting to different areas in fall, etc. Make no mistake: There’s no such thing as a magic water temperature or comfort zone that you look for throughout the year. Instead, water temperature provides only clues to fish location and behavior, based on a predictable seasonal progression.
Periods Of Fish Response Very few anglers are also biologists, limnologists or ichthyologists—which is okay. We do not need to know the exact scientific reasons certain things in nature occur as they do. Rather, if we simply recognize that certain sequential events occur, we can predict when they might take place within a rough timeframe.
If you’ve fished for any number of years, your experience likely suggests what fish may be doing at a given time of year, because they were doing the same thing at the same time the previous year, give or take a few days or weeks. It’s tempting to simply call it seasonal behavior, but it’s much more complex, and divided into far more individual stages than the four seasons we all relate to. So we need a different term.
Over the years, we’ve learned to more aptly break the fishing year down into Fish Response Periods. When you view all of these periods in sequence, it forms an annual Fish Response Calendar. Yet because the timing of bass behavior varies so much based on how far north or south bass live, we do not attempt to place any dates on the calendar. Rather, it shows the sequence of Fish Response Periods bass experience throughout the year.
For example, bass in Southern impoundments experience short winters, followed by extended spawn, summer and other Fish Response Periods that gradually blend into each other over a period of roughly nine months. By comparison, bass in Northern natural lakes live as much as six months of the year beneath winter ice cover.
Once ice leaves the lake, the succession of remaining Fish Response Periods tends to occur in fairly rapid fashion over six to eight months, with the transitions between periods being more sharply defined and obvious than those in southerly latitudes. Yet no matter where you fish, you can be on the lookout for environmental signs that help you anticipate coming changes in the bass’ annual cycle.
Many years ago, when we first originated these concepts, we divided the angling year into 10 Calendar Periods. In the ensuing years, we came to realize that there were actually 11 Calendar Periods, and that we needed to add a distinct period between Winter/Ice and Prespawn. We’re going to call it Ice- Out/Spring Cold Water Transition. It’s a real mouthful. But there’s a reason for the terminology.
In Southern lakes that don’t freeze, Winter is best described as an extended period of the coldest water of the year. In the North, we call the same period Ice.
Following relatively short winter conditions, ice-free Southern waters begin to warm, sending a signal to fish that it’s time for a change. The change is more of a slow transition process in which bass slowly begin to react, fading from one Response Period into another. But in the North, Ice-Out—the sudden loss of ice cover in spring—is a dramatic event, sending an immediate signal to bass that it’s time to move.
Instinctive Vs. Seasonal Stimuli With the benefit of experience and hindsight, let’s move forward using 11 Fish Response Periods to describe annual bass behavior. Some of these periods are based upon the fi sh species itself (in this case, largemouth bass), while others revolve more around general seasonal conditions.
For instance, in all fish life cycles, location and behavior centers on spawning-related activities for a relatively brief, but critical, time each year. Bass location and behavior during their spawning cycle—the Prespawn, Spawn and Postspawn periods—is driven by strong reproductive urges.
Once the spawning cycle is complete, however, things change dramatically and their behavior is driven by other requirements. During the rest of the year, bass location and activity is dictated by their need for comfort, safety and food.
Bass fulfill those needs by moving to and taking advantage of the best options that the local environment currently offers. And as those options change, fish adjust their location and behavior accordingly, based on what is available in terms of forage, aquatic vegetation, water temperature, etc. In other words, they react to the current ecological conditions present in the body of water in which they live.
Because bass spawn at different water temperatures and times than other gamefish like walleyes and pike, the timing of their Prespawn, Spawn and Postspawn periods do not coincide. Yet as summer begins, bass and other species all begin reacting to the same environmental conditions and stimuli, and their Prime Summer, Midsummer and Postsummer periods largely coincide throughout the summer months.
And as the water cools into fall and winter, periods like Fall Turnover, Fall Cold Water and Winter are simply determined by water temperature, which is easily observed and measured.
At this point, don’t get hung up on small, insignificant details, or on grandiose theories of fish lifestyle. This is not a scientific thesis. Rather, the Fish Response Periods were designed so that you can easily recognize them and react accordingly, wherever and whenever you fish.