水中から見たスモールマウスバスのスポーニングシーン： ダイバーが目撃した驚きの光景

Underwater visibility is fantastic. I can see at least 30 feet (10 m) horizontally, which is superb for New England waters. I am looking for a male smallmouth bass….

In early spring when water in the shallows warms to the low-to-mid fifties Fahrenheit, the male smallmouth bass venture into shallow, rocky coves and shorelines.

The smallmouth bass I am looking for will be moving quickly, trying to coerce a female bass to the nest he has constructed on the lake bottom.

Male smallmouth bass seek an area on the bottom that has just the right mix of clean sand and cobblestones. Typically, this area will have a large rock, sunken tree, or ledge near-by. Waters where nest sites are selected are usually 6 feet (2 m) or less in depth.

The bass, satisfied with the area, will begin to sweep away coarse materials, silt, and debris with its caudal, or tail, fin. The end result will be a circular depression 2 or 3 feet (.5-1 m) in diameter and 2-4 inches (5-10 cm) deep. This process may be repeated several times in other locations before the male is satisfied with his handiwork.

As the water continues to warm between 55° and 58°, female smallmouth bass approach spawning areas from deeper water. As the females approach this area, their coloration is transformed into a series of dark vertical markings called bars. When a male sees a female, he rushes toward her and attempts to drive her to the nest site. At first the female swims rapidly away, only to return later.

The male circles the female and nips her to try to drive her to his nest. Near the nest site, the male and female circle the nest in the typical push-lead behavior.

Circling in the nest is often accomplished with the male outside the female, working their way around the nest. The female gently swings her head and tail from side to side. Occasionally she may rise from the nest in a head-down position.

After the female has laid her eggs, the male chases her away from the nest.
Now the male will either attract more females to the nest for spawning, or begin guarding the eggs.

These eggs are pale gray and yellow and are very sticky. They adhere to each other and to the stones in the bottom of the nest. Incubation takes about 10 days at 54° Fahrenheit.
The male is so protective of his brood, he will often attack on-lookers who venture too close for comfort, regardless of their size.

After about thirty minutes of searching, I notice a male trying to chase a female to the nest he has constructed! I observe the female rapidly changing colors and developing dark, vertical bars along her body. This is it!

I kick hard with my dive fins to try to keep up with the pair as he moves her over 30 feet (10 m) away to his nest site. I breathe hard through my regulator, trying to keep up with them.

The male will not feed again until the young bass leave the nest site several weeks later. He will strike at anything that enters the nest area, but only in defense of his young.

Newly hatched fry are approximately 1/5 inch (5 mm) in length and are nearly transparent. They live in the nest bottom as they gradually absorb their yolk-sacs.

As their yolk-sacs disappear, the young fry begin to feed. Now they turn jet black in color—the stage from which the name “black bass” came. Black fry rise over the nest in a dense swarm and continue to feed under the watchful eye of the guardian male.

As the size of the fry increases, the black fry slowly transform into the green fry stage, the coloration of a typical smallmouth bass. At this point, the green fry disperse into shallow, rocky areas that afford protection and food.

The male bass will now leave the nest site and begin a period of recovery, for he has not fed since spawning several weeks earlier. At this point he will return to his home range area and feed on crayfish, minnows and other available small fish.

In approximately five years, the fry will be mature and ready to spawn.