Abalone reach sexual maturity at a small size, and fertility is high
and increases exponentially with size. Sexes are separate and fertilization
is external. The Abalone eggs and sperm broadcast into the water through
the Abalone pores with the respiratory current. A 1.5 inch abalone
may spawn 10,000 eggs or more at a time, while an 8 inch abalone may
spawn 11 million or more eggs. The Abalone spawning season varies among
species with black, green and pink abalone spawning between spring
and fall, and pinto abalone spawning during the summer. Red abalone
in some locations spawn throughout the year. The Abalone fertilized
eggs hatch into floating larvae that feed on plankton until their shells
begin to form. Once the Abalone shell forms, the juvenile abalone sinks
to the bottom where it clings to rocks and crevices with its single
powerful foot. Settling rates appear to be variable. After settling,
abalones change their diet and feed on macroalgae.
Except for black abalone, hybridization for abalone species is not
uncommon in areas where several species occur together. There are 12
recognized hybrids in southern California and northern Baja California.
Limited growth information is available for abalones. Commercial sizes
of 6.25 inches for pinks, seven inches for greens and 7.75 inches for
reds are reached after a minimum of 10 to 15 years in southern California.
Pinto abalone reach about 2.5 inches in a minimum of 6 years.
Juvenile abalones feed on rock-encrusting coralline algae and on diatom
and bacterial films. Adult abalones feed primarily on loose pieces
of marine algae drifting with the surge or current. Large brown algae
such as giant kelp, bull kelp, feather boa kelp and elk kelp are preferred,
although other species of algae may be eaten at various times.
Abalone eggs and larvae are consumed by filter-feeding fish and shellfish.
Predators of juvenile abalones include crabs, lobsters, gastropods,
octopuses, seastars, and fishes. The bat ray in southern California
and the sea otter in central California prey selectively on larger
abalones.
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