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Largemouth Bass (Micropterus salmoides)


Largemouth bass are a popular warmwater gamefish introduced into many
streams and reservoirs in California. Largemouth bass are typically found in low
to mid-elevation lakes and reservoirs, but are also common in foothill streams in
the San Joaquin Valley. They prefer slow moving water with abundant aquatic
vegetation, but occur mostly in disturbed areas.

Adult largemouth bass are solitary hunters and frequently establish home ranges
around a submerged structure. Young bass school in the open shallows close to
shore. Largemouth bass are most active during the day, and feed most actively
during dusk.

Largemouth bass fry begin feeding on rotifers and crustaceans. As they grow,
their diet includes fish fry (including their own species) and aquatic insects. Bass
larger than 10 cm TL will feed almost entirely on other fishes, but other prey
items may include crayfish, frogs and tadpoles. Individual bass may also be
selective in their feeding habits, preferring one prey item over another, or one
species of fish to another.

Growth is dependent on a number of factors. Genetic background, competition,
food availability and water temperature are among the more important variables
that affect growth in largemouth bass. Younger bass are probably most affected
by competition for the available food. Their food preferences are widely shared
with other species of fish.

Largemouth bass mature during their second or third year. Males begin to build
nests when water temperatures begin to warm in the spring. Nests are shallow
depressions in rock, gravel or debris-littered substrate in water 1 to 2 meters in
depth. Nests are solitary, and guarded and maintained by the males. Females
signal their readiness by repeatedly returning to the nest. After the male accepts
her, the two will circle the nest, and the male will nip at her sides. When the two
are ready, the female lowers herself to the bottom of the nest and rubs her
abdomen there. The two then release sperm and eggs and the eggs adhere to
the substrate. The female then leaves the nest or is chased away by the male.

The nest is guarded by the male until the eggs hatch, which is usually three to
ten days. The male continues to guard the newly hatched fish by herding them
inside the nest. By the time the fry are approximately 3 cm, they are too active to
keep inside the nest, and they disperse into shallow water.

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