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Bass Biology
Fishing the Spawn
By Wayne Gustaveson

July/August 1994

There is nothing better than bass fishing during the height of the spawn. The bass are shallow, aggressive, and consistently larger than those caught at many other times of the year. The comment is often heard from those that like to keep an occasional bass to eat, that we need to throw back this fat female so she can spawn. Instead, we will keep this scrawny little male with the frayed tail for supper.

That theory works well for deer and elk; harvest the males, let the females perpetuate the species. But in the underwater world of black bass, that notion is "bass ackwards". The male bass is responsible for the survival of the new year class of bass. The female is just window dressing.

Bass spawning is triggered by photoperiod (day length) and water temperature. At Lake Powell the first spawns of the spring happen any time after the last week of March when the water warms to 60° F. Males then move into the shallows and sweep the silt away from a one to two-foot area exposing the rocky substrate. The preferred nest depth is from 18 to 36-inches. Largemouth like a bush or some type of overhead cover nearby. Smallmouth often use a ledge or select a nest near a boulder to feel the security of cover close at hand.

Once a nest site is excavated the male will stay near it for the duration of the spawning season. He may change nest sites if the water becomes too shallow or too deep, but if conditions are right, he stays there until the water warms enough to preclude spawning for the year.

In some years, spring never arrives. One cold front after another blows through and the water never warms to 60° F. Spring spawning bass are equipped to handle the situation. Males build and occupy nests when the temperature rises. When the temperature falls, bass abandon the nest. If the warm spell persists long enough to produce a spawn, falling temperatures will still cause the nest to be abandoned and most of the eggs lost. The tendency to abandon the nest is nature's way of making the best of unstable spring weather. Declining temperatures in the spring are usually marked by cold winds which tend to destroy nests as the waves pile up on the shore where the eggs are covered with silt, and the fry smother. Bass don't stay with that nest full of dead eggs.

As soon as the water warms again, the male tidies up the rocks by sweeping out the silt and then spawns again. Fry survive best when water is warming and weather is stable. If it stays warm, the male guards the nest until the eggs hatch and then protects the fry for the first week or so. An individual male can re-nest as many as 8 to 10 times during a single spring spawning season.

Females make adjustments to achieve the same goal. The ovary contains 2,000 to 100,000 eggs depending on the size and age of the female. Not all eggs mature at the same time. During the first warm spell a portion of the eggs will ripen. If selected by a male the female could then spawn about 2,000 eggs in his nest. She would then wait a day or two and be ready to spawn another 2,000 eggs. She could continue to spawn 10 to 20 more times depending on weather conditions and availability of males. If not selected she may not spawn at all, even though she is able and willing. Healthy female bass always have many large, yellow but unripe eggs in the ovary. Catching female bas with a fully developed ovary long after spawning season is over is the rule instead of the exception.

The female selection process is reminiscent of cow cutting – for the rodeo fans out there. When everything is ready the male leaves the nest and journeys into deeper water where the females are stationed. He somehow finds the appropriate female (my guess is that he chooses the first female encountered). He veers around behind her and then drives her toward the nest. They zig-zag back toward the nest as she coyly tries in vain to get back into deep water.

When she is parked over the nest, he employs cave-man manners and smartly rams her in the stomach with his snout. The impact breaks lose the ripe eggs and allows them to flow. She begins squirting eggs near the rock nest but gradually rises toward the surface, her body turning partially on the side, as the male gently rises to the surface beside her. She changes color in the process with the side bars and markings becoming much more prominent and the green skin color becoming much paler during egg deposition. When her complement of eggs is emitted, the male drives her away and rounds up another female. He will spawn with as many females as possible for a 6 to 12-hour period after which he drives away all intruders.

There is always an abundance of females to lay the eggs. The male initiates courting and is then responsible for all caretaking until the young bass are able to survive on their own.

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