EPA's Vessel General Permit and Small Vessel General

Natural threats
Natural pressures exist from sea otter predation (Johnson et al. 2009) and the low density of
individuals during spawning events. Interspecific competition has not been studied in white
abalone, but blacklip abalone face significant competition for algal resources by sea urchins
(Strain and Johnson 2009).
Anthropogenic threats
White abalone numbers were severely reduced due to excessive harvest. This has led to belowthreshold
spawning densities in many areas that are blamed for the inability of the species to
recover. Although small-scale aquaculture takes have occurred to attempt captive breeding and
recovery, these takes are small in number. Otherwise, substantial human harvesting is not
known. No commercial or recreational takes are permitted under ESA protection.
Although toxicology of abalone is poorly known, red abalone have demonstrated metabolic
breakdown when exposed to the pesticide 3-trifluoromethyl-4-nitrophenol (Viant et al. 2001).
Silver, cadmium, and mercury are also known to bioaccumulate in abalone, likely from ingested
algae (Huang et al. 2008). Update rates have been measured as 1.78 L g -1 d -1 for silver, 0.056 L
g -1 d -1 for cadmium and 0.32 L g -1 d -1 for mercury, of which 58 to 83%, 33 to 59%, and 65 to
78%, respectively, is assimilated. Abalone are known to bioaccumulate high levels of heavy
metals in the presence of high environmental concentrations (Wang et al. 2009).
Changes in sea surface temperatures have been suggested as a driving force in altering red
abalone distribution in the past (Braje et al. 2009); it is unknown what affect, if any climate
change may have on white abalone.
Critical habitat
Critical habitat has not been designated for white abalone.
Black abalone
Distribution
Black abalone historically occurred between Coos Bay, Oregon, and Cape San Lucas, Baja
California (Cox 1962), but were rare north of San Francisco (Morris et al. 1980). Distribution
extended to the Channel Islands and from Cedros to Punta Asuncion along Baja, Mexico
(Guzmán Del Proó 1992). Present occurrence remains throughout much of this range, although
greatly reduced.
Growth and reproduction
Spawning occurs during spring and summer (Cox 1960). Synchronicity of gamete release is
vital, as likelihood of fertilization is reliant upon dense adult aggregation and subsequent high
egg and sperm density (Davis 1996). Fecundity increases exponentially with size, with small
mature females producing a few hundred thousand eggs each year, but older individuals
producing 10 to 15 million eggs (Hahn 1989). Fertilized eggs sink and hatch into free-swimming
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