Spawning activity of largemouth bass can be broken into three distinct stages. Where you find the fish and how they behave depends on what stage of the spawn they are in.
• Pre-Spawn. When water temperatures rise into the upper 40s, largemouth begin moving out of their deep winter haunts. They congregate on shallow flats that are easily warmed by the sun. In natural lakes, they move into shallow, weedy bays, boat channels and harbors. In man-made lakes, they’re drawn to shallow flats adjacent to old river channels or to creek channels, brushy upper ends of creek arms and wooded coves. In big rivers, you’ll find them in weedy sloughs, side channels and stump fields.
Because of their developing gonads, the fish require more energy than normal, so they are feeding heavily. But they’re very susceptible to cold fronts, which drive them back to deeper water and slow or stop their feeding activity.
• Spawn. Spawning is triggered by a combination of water temperature and day length. Male largemouth begin fanning out nests in the shallows when the water temperature rises into the 60s and stays there for a few days.
A period of very warm weather in early spring may quickly bring the water temperature in the shallows up to the 60s. But that doesn’t necessarily mean that largemouth will start to spawn. Their biological clock, which is controlled by day length, tells them that the time is not yet right. Warmer than usual water temperatures may move spawning ahead by a few days, but seldom more than that.
If spawning were regulated by water temperature alone, there could be grave biological consequences. In an early spring, the fry would hatch much earlier than normal, making them that much more vulnerable to an early spring cold front that could wipe out the supply of plankton that the fry need for food. The result would be mass starvation that would wipe out much of the year class.
Largemouth normally nest in an area that is sheltered from the wind, usually around weedy or woody cover. Using his tail, the male fans away silt to reach a firm sandy or gravelly bottom. Then the female moves in to deposit her eggs.
The fish generally build their nests in the vicinity of their pre-spawn locations, usually moving a little shallower to find a suitable bottom or some type of cover. In natural lakes, you’ll often find spawning beds on sand-gravel areas along an otherwise muddy shoreline or around old patches of lily pads, maidencane or bulrushes from the previous year.
In man-made lakes, the fish usually nest in or on tree roots, around brush piles or in some other type of woody cover.
In big rivers, most spawning takes place in weedy backwaters, but the fish may also spawn in woody cover in side channels with light current.
By the time the water temperature reaches the upper 60s, most spawning has been completed. The male guards the nest and remains with the fry until they disperse.
• Post-Spawn. Female largemouth are notoriously difficult to catch following completion of spawning. Not only are they feeding sporadically as they recuperate from the rigors of spawning, they may be hard to find as they make their way from their spawning sites to the deeper structure where they will spend the summer.
Males, however, are easy to catch as long as they are guarding the nest. They too are feeding only sporadically, but they will attack anything that comes too close to the nest, including an angler’s lure. But catching nest-guarding males is frowned upon by most of the bass-fishing community. Once the male is removed, sunfish and other panfish can easily raid the nest, quickly eating most of the defenseless fry.
• Duration of Spawning Period. In the northern part of the largemouth’s range, the entire spawning period (pre-spawn through post-spawn) lasts only 2 or 3 weeks. Because the water warms so rapidly, spawning activity is compressed into a much shorter period than it is in the southern part of the range.
In Florida, for example, some fish may start to spawn in January while others may not begin until late March. Consequently, anglers can find bass on the spawning beds for a period of two or even three months, depending on how fast the water warms.