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SPECIAL STATUS SPECIES: BLACK ABALONE (Haliotis cracherodii)
NATURAL HISTORY |
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| General |
| Taxonomy: |
Abalone
are members of the phylum Mollusca (bivalves, slugs,
squids, snails, etc.), the family Haliotidae and
the genus Haliotis. Seven species of abalone
are found in California.
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| Appearance: |
Maximum
shell length exceeds 200 mm, although the
average is much smaller (~115 mm).1,6 The epipodium (the
circular fringe of skin around the foot) and tentacles
are jet-black and the underside of the foot is creamy
white. The outer surface of the shell is black, dark
blue or greenish-black, and smooth (usually not covered
with encrusting organisms). They shell usually has
5-9 open holes with edges that are flush (i.e. not
raised) with the shell surface. The inside surface
of the shell is pearly with pink and green iridescence
and no muscle scar. The muscular foot creates strong
suction that allows the animal to attach tightly to
hard surfaces. |
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| Feeding Behavior |
| Overview: |
Abalone are herbivores
that feed on intertidal and subtidal species of algae.
Through their grazing activities, black abalone prevent
many species of sessile invertebrates from colonizing
the rock surface. In areas with black abalone, the
species assemblage is dominated by bare rock and crustose
coralline red algae.9,11 |
| Food
Items: |
Juvenile
black abalone (and adults when other food is not available)
feed on rock-encrusting coralline algae and on diatom
and bacterial films.27
Adult black abalone feed primarily on loose pieces
of algae drifting with the surge or current. Large
brown algae such as giant kelp, bull kelp, and feather
boa kelp are preferred, although other species of
algae may be eaten at various times.27 |
| Method
of Capture: |
Juveniles
scrape food from the rock surface using the radula,
a file-like structure in the mouth. Adult abalone
position themselves in areas where surge or water
currents deliver a supply of drifting algae. The abalone
catch the algae as it drifts by. |
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| Reproduction |
| Overview: |
All species of abalone share
the same reproductive strategy called broadcast spawning.
Males and females release sperm and eggs into the
water column and rely on high gamete densities for
successful fertilization. This reproductive strategy
requires densely aggregated adults for success. In
areas where abalone densities are too low (below the
minimum viable population size), fertilization is
not likely.13 |
| Time to Maturity: |
Most black abalone
reach sexual maturity at a size of 40-44 mm; two or
more years are needed to reach this size.13
Growth rates can vary depending on food availability,
water temperature, and other environmental factors.13 |
| Longevity: |
Abalone are long-lived
and can live in excess of 30 years.4
Twenty or more years are required to reach maximum
length.4 |
| Spawning
Season: |
Black abalone
usually spawn sometime between late spring and late
summer.13,28 |
| Frequency of
Spawning: |
Not known, but probably annual |
| Larval Period: |
Black abalone larvae
are free-swimming and settle to the bottom when they
are 5-14 days old (based on laboratory studies).6
Based on studies of settlement in other species of
abalone, larvae may require contact with crustose
coralline red algae for settlement and metamorphosis
into juveniles.6 |
Offspring per
Spawning Attempt: |
The number of eggs
a female produces increases with size.13
Newly mature females produce only a few hundred thousand
eggs each year, whereas older individuals produce
10-15 million eggs.30 |
| Parental
Care: |
None |
| Mating
System: |
Broadcast spawning.
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