EPA's Vessel General Permit and Small Vessel General

larvae within 72 hours. After one or two weeks, larvae settle (CDFG 1993). Larval mortality is
assumed to be high (Leighton 1972). At 1.5 inches (roughly 3 years of age), black abalone are
considered sexually mature (Blecha et al. 1992). Size at sexual maturity appears to decrease
with latitude, suggesting precocity in southern portions of the range (Munoz and Camacho 1976,
Guzman del Proo et al. 1980).
Feeding
Black abalone eat algae, with larvae eating pelagic plankton and postlarvae feeding upon on
bacterial films, benthic diatoms (Cox 1962, Ault 1985), and coralline algae. Juveniles and adults
feed upon large-bodied algae, such as giant and feather-boa kelp (Cox 1962, Howorth 1978).
However, low food resource availability has been shown to stunt growth in blacklip abalone
(Saunders et al. 2009a, Saunders et al. 2009b).
Habitat
Black abalone occupy rocky intertidal and shallow subtidal zones (Haaker et al. 1986). Depth
distribution is usually from the shore to about 10 feet of water depth. Mobility patterns are size
dependent (Blecha et al. 1992). Individuals above 4.1 inches undergo limited movement in
exposed rocky locations. Juveniles (smaller than 1.6 inches) remain within rocky crevices
during daylight hours, but become more active at night (Cox 1960). At 3 to 4 inches in length,
when they emerge into more open rocky habitats where food may be more abundant (Haaker et
al. 1986). Movement patterns have been further characterized in green lip abalone by Cennie et
al. (2009a), where individuals belonged to either a sedentary or a wandering clade (which moved
over larger areas and covered greater distances, occupied inner portions of hides more
frequently, responded more rapidly to food odor, foraged for longer periods, and displaced
conspecifics from food patches).
Life span
Black abalone lifespan is unknown, but abalone are believed to survive for 30 years or more
(Blecha et al. 1992).
Status and trends
On January 11, 2008, NMFS published a proposed rule to list black abalone as endangered under
the ESA (73 FR 1986). Species decline is reflected by the decrease in commercial catches until
1993, when commercial harvests were halted. Historic levels approached 2,200 tons in
California in 1879 and declined to around 1000 tons in the 1970's. Commercial landings then
decreased to 19.1 tons in the last year of harvests, when mortality from withering syndrome
devastated remaining black abalone stocks throughout southern California (Haaker 1994). Over
20 years, densities of more than 100 individuals per cubic yard disappeared from most of their
former range south of Point Conception (Davis 1993). A similar mass mortality was reported at
Palos Verdes Peninsula in the late 1950's, where average density decreased from more than 2.8
individuals per square yard from 1975 to 1979 down to about 0.03 individuals per square yard
from 1987 to 1991 (Cox 1962). Island habitats experienced more severe trends; 99% of black
abalone vanished from Anacapa, Santa Barbara, and Santa Rosa Islands in less than 5 years
(Haaker et al. 1989, Richards and Davis 1993).
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