(DRAFT) - Taxonomy
Species crab, yellow rock
Species Id M070019
Date 26 AUG 96
TAXONOMY
NAME - crab, yellow rock
OTHER COMMON NAMES - rock crab and gold crab
ELEMENT CODE -
CATEGORY - Aquatic Crustaceans
PHYLUM AND SUBPHYLUM - Arthropoda,
CLASS AND SUBCLASS - Crustacea, Malacostraca
ORDER AND SUBORDER - Decapoda, Repantia
FAMILY AND SUBFAMILY - Cancridae,
GENUS AND SUBGENUS - Cancer,
SPECIES AND SSP - anthonyi,
SCIENTIFIC NAME - Cancer anthonyi
AUTHORITY - Rathbun
TAXONOMY REFERENCES - 261
Taxonomy - 1 (DRAFT) - Status
Species crab, yellow rock
Species Id M070019
Date 26 AUG 96
STATUS
Coded Status
Sport Fish
Commercial
Existing, FMP exists
REFERENCES FOR STATUS - 261
COMMENTS ON STATUS -
Rock crabs had been fished previously at a low level of effort since at
least 1930. Commercial fishery landings statistics of CDFG showed that
annual landings in the mid-1980's approached 2 million lb with an ex-vessel
value exceeding $1.6 million. Declines in the stocks of other commercially
important nearshore species have stimulated interest in further use of rock
crab species; continued growth of the fishery is expected. The species also
supports small recreational fishery.*261*
In California, the sport catch limit on all Cancer species in combination
(excluding the Dungeness crab) is 35 crabs per day, and the minimum legal
carapace width is 4 inches.*261*
Rock crabs occupy a variety of coastal habitats and are an ecologically
important component of the nearshore environment. As juveniles, they are
important prey of numerous invertebrates and many commercially and
recreationally important fishes. Adult rock crabs are a major food of the
threatened southern sea otter (Enhydra lutris) along the central California
coast.*261*
Status - 1 (DRAFT) - Distribution
Species crab, yellow rock
Species Id M070019
Date 26 AUG 96
DISTRIBUTION
Distribution - 1 HABITAT ASSOCIATIONS
HABITAT - AQUATIC
REFERENCES FOR HABITAT - 261
LAND USE -
Water
REFERENCES FOR LAND USE - 261
NATIONAL WETLAND INVENTORY CODES
NWI NWICLS NWIMOD NWISPEC
Estuarine, intertidal RB.
Estuarine, intertidal RF.
Estuarine, intertidal RS.
Estuarine, intertidal UB.
Marine, intertidal RB.
Marine, intertidal RF.
Marine, intertidal RS.
Marine, intertidal UB.
REFERENCES FOR NWI - 261
COMMENTS ON HABITAT ASSOCIATIONS -
Its habitat extends from the low intertidal zone, including
bays and estuaries, to a subtidal depth of 140 m; it inhabits mostly
silty sand to mud substrates and the sand-rock substrate ecotone of
rocky reefs.*261*
Habitat Associations - 1 (DRAFT) - Food Habits
Species crab, yellow rock
Species Id M070019
Date 26 AUG 96
FOOD HABITS
TROPHIC LEVEL -
CARNIVORE
SCAVENGER
REFERENCES FOR TROPHIC LEVEL - 261
LIFESTAGE FOOD FOOD PART
General Bivalve Molluscs Not Specified
General Snails Not Specified
General Echinoderms Not Specified
General Crustaceans Not Specified
Food Habits - 1 (DRAFT) - Environment Associations
Species crab, yellow rock
Species Id M070019
Date 26 AUG 96
ENVIRONMENTAL ASSOCIATIONS
G = General A = Adult
LIM = Limiting RA = Resting Adult
J = Juvenile FA = Feeding Adult
RJ = Resting Juvenile BA = Breeding Adult
FJ = Feeding Juvenile P = Pupae
L = Larvae E = Egg
RL = Resting Larvae
FL = Feeding Larvae
LIFESTAGE ENVIRONMENTAL ASSOCIATIONS
G Bottom Type [Aquatic]: Sand
G Bottom Type [Aquatic]: Sand
A Water Depth Preference: Specified in Comments
J Water Depth Preference: Specified in Comments
L Water Temperature: Specified in Comments
L Bottom Type [Aquatic]: Sand
G
G
REFERENCES FOR ENVIRONMENTAL ASSOC_ - 261
REFERENCES FOR ADULT ENVIRONMENTAL ASSOC_ - 261
REFERENCES FOR JUVENILE ENVIRONMENTAL ASSOC_ - 261
REFERENCES FOR LARVAE ENVIRONMENTAL ASSOC_ - 261
COMMENTS ON ENVIRONMENTAL ASSOCIATIONS -
The yellow crab lives almost exclusively on sand substrata; consequently
the "rock crab" designation is somewhat misleading although the species is
often found at the interface of rock and sand habitats, and adjacent to
artificial reefs.*261*
No tolerance levels have been established for the larval life history
stages of rock crabs, but researchers found that low salinities impaired
the molting process in larvae of the closely related Dungeness crab.*261
COMMENTS ON ADULT ENVIRONMENTAL ASSOC_ -
Adult yellow crabs are most common at depths of 18-55 m.*261*
COMMENTS ON JUVENILE ENVIRONMENTAL ASSOC_ -
In southern California the densities of juvenile crabs ere higher than
those of the brown rock crabs and red rock crabs; the young were collected
almost exclusively from sand substrata in depths less than 33 m.*261*
COMMENTS ON LARVAE ENVIRONMENTAL ASSOC_ -
Researchers who conducted field experiments to determine preferred sustrate
types of newly settling rock crab larvae in southern California, observed
that first crab instar yellow crabs were most abundant on sand and least
abundant on rock substrates.*261*
Environment Associations - 1 (DRAFT) - Environment Associations
Species crab, yellow rock
Species Id M070019
Date 26 AUG 96
Researchers found that a temperature increase of about 4 degrees C
significantly accelerated the rate of larval development of yellow crabs
reared in the laboratory. The average duration of each instar was longer
at 18 degrees C than at 22 degrees C, resulting in an average total
development time of 45 days at 18 degrees C but only 33 days at 22 degrees
C.*261*
Environment Associations - 2 (DRAFT) - Life History
Species crab, yellow rock
Species Id M070019
Date 26 AUG 96
LIFE HISTORY
PHYSICAL DESCRIPTION:
All Cancer species are recognized by their broad, oval, uneven but not
highly sculptured carapace which has numerous anterolateral teeth. Males
are distinguished by a slender abdomen and mature females by a broad abdomen
that is often hirsute on the margin. Researchers, who studied the
morphological relationships of 10 northern temperate Cancer species,
considered the brown rock crab, red rock crab, and yellow crab closely
related primarily on the basis of similarities in claw shape.
Adult yellow crabs are light brown to pale yellow dorsally and uniformly
light yellow ventrally, without red spotting beneath. The carapace is
widest at the ninth of 10 anterolateral teeth. The tips of the claws are
partly or almost entirely darkened and the walking legs are generally
without hair. Coloration of juveniles tends to be darker than that of
adults, ranging from brown to gray. Yellow crabs are allied to the brown
rock crabs, but have broader and less projecting anterolateral teeth, and
less hairy legs.*261*
REPRODUCTION:
The female mates in the soft-shell condition, after molting. Soft-shell
female rock crabs are most common in spring and fall, though they may be
found throughout the year. A pheromone released in the urine of females
before they molt attracts males and stimulates mating behavior. Brown rock
crabs are stimulated to pre-copulatory position and activity by pheromone
concentrations as low as 10(to the -10) moles/l. The male carries the
female, before her ecdysis, through insemination, and until initial
hardening of her shell occurs. Mating involves insertion of the male
gonopod into the spermatheca of the female and deposition of a
spermatophore. Spermatophores contain sperm that is potentially viable for
a year or longer, for multiple spawnings. Mated females (in the "plugged"
condition) may be identified by the presence of the hardened spermatophore
deposited in the spermatheca by the male, which presumably blocks further
mating and prevents loss of sperm. The plug is ejected during the first
oviposition; multiple ovipositions may occur but no record of them has been
published.*261*
Eggs and Fecundity. The eggs are fertilized internally as they are extruded,
about 11 weeks after the mating, and are carried by the female during
development. They appear as a bright orange mass ("sponge") attached to
setae on the endopodites of the pleopods, beneath the abdominal flap.
Clutch size in the yellow crab averages over 2.6 million eggs.*261*
Larvae. Larvae hatch as prezoeae and molt to first stage zoeae in less than
1 h. They advance through six stages of successive increases in size-five
zoeal and one megalopal. During their planktonic existence, crab larvae
become widely distributed over the continental shelf. Researchers found
that, in central California, estuarine runoff and upwelling probably
dispersed Dungeness crab zoeae offshore, and the northward flowing Davidson
current dispersed larvae upcoast in winter. Researchers presented evidence
that early stage larvae of rock crabs generlly occurred on the bottom, or in
depths up to 80 m, during the day; late stage larvae, however, were more
abundant near the surface. It was suggested that a combination of physical
factors, primarily wind-generated surface currents and tidally forced
interanl waves, caused megalopae to be transported shoreward.*261*
Life History - 1 (DRAFT) - Life History
Species crab, yellow rock
Species Id M070019
Date 26 AUG 96
Juveniles. Most megalopae molt into juveniles (first crab instars) in late
spring or summer months. Despite a widespread spatial and temporal overlap
of larval distribution in coastal waters, certain species-specific patterns
of recruitment vary with depth and substrate.*261*
BEHAVIOR:
Movements. The few tag-and-recapture data available indicate that adult
rock crabs remain fairly close inshore; localized movements rarely exceed
several kilometers from their release sites. Trap placement and
fishing success may strongly bias the interpretation of recapture or
movement data. Crabs were more likely to enter a trap if the
opening was perpendicular to prevailing currents.*261*.
LIMITING FACTORS:
Predation. Benthic fishes are major predators on juvenile rock crabs; among
the many that are known are scorpionfish (Scorpaena guttata), cabezon
(Scorpaenichthys marmoratus), barred sand bass, and severl species of
rockfishes. The sand star Astropecten verilli has been identified as a
major invertebrate predator on juvenile yellow crabs. Larger crabs
eventually attain a size large enough to preclude predation by most fishes,
except when the shell is soft, just after molting. Rock crabs may fall prey
to southern sea otters. Rock crabs are also the preferred prey of octopuses
in southern California, and have been found in the gut of bottom-foraging
sharks in Elkhorn Slough, central California.*261*
The nemertean egg predator Carcinonemertes epialti often occurs in the egg
masses of rock crabs.*261*
POPULATION ATTRIBUTES:
Growth. Growth in rock crabs, as in all crustaceans, progresses as a step
function through a series of molts. In brown rock crabs the maximum
carapace width is at least 155 mm in males (measured at the widest point on
carapace, excluding the anterolateral spines) but does not exceed 145 mm in
females. Longevity has been estimated to be about 5-6 years for brown rock
crabs. Size increases are slightly greater in males than in females. In
brown rock crabs, size difference in claws is a sexually dimorphic
characteristic that occurs at the pubescent molt, males attaining larger
claws than females. Unsexed juveniles has a constant ratio of claw height
to carapace width up to a width of 65 mm. Beyond this size, the ratios in
males and females diverged from juvenile proportions. Discontinuities in
growth rates of appendages were more distinct in males than in females.
Molting appears to occur most frequently in rock crabs during fall and early
winter, although it may occur throughout the year.*261*
Commercial Harvest. Rock crabs have historically supported only a
relatively minor fishery in California, particularly when compared with the
fishery of the Dungeness crab. The rock crab fishery has grown steadily
since landings of about 20,000 lb were reported in 1950. Annual landings
exceeded 1.2 million lb in 1976 and approached 2 million lb in 1986.
Commercial landings show no well-defined trends in seasonal crab abundance.
Monthly landing totals may be a misleading indicator of seasonal abundance
because total fishing effort varies and marketable crab size may fluctuate
with consumer demand. Experimental trapping studies, however, indicate a
trend toward the catches being highest in fall and lowest in summer.
Higher catches in central California were positively
Life History - 2 (DRAFT) - Life History
Species crab, yellow rock
Species Id M070019
Date 26 AUG 96
correlated with annual maximum water temperatures and an increased
proportion of female crabs in the catches.*261*
The variability in the harvest of crabs in southern California has been
historically linked to the changing success of other commercial fisheries.
In particular, the rock crab fishery is closely associated with the
California commercial fishery for spiny lobsters, in terms of seasonal
effort, gear, and methods. Fishermen can easily switch to trapping crabs in
the "off-season" or when catches of lobsters are low. Lobster gear has been
widely used for harvesting crabs.*261*
Recreational Harvest. The crabs are taken mainly in small numbers with
baited hoop nets near piers and jetties, and by hand by sport divers. This
harvest is insignificant compared with the total commercial harvest. In
California, the sport catch limit on all Cancer species in combination
(excluding the Dungeness crab) is 35 per day, and the minimum legal carapace
width is 4 inches.*261*
REFERENCES FOR LIFE HISTORY- 261
Life History - 3 (DRAFT) - Management Practices
Species crab, yellow rock
Species Id M070019
Date 26 AUG 96
MANAGEMENT PRACTICES
RESULT MANAGEMENT PRACTICE
Adverse Drilling
Adverse Applying other toxicants
REFERENCES FOR ADVERSE MANAGEMENT PRACTICES - 261
COMMENTS ON MANAGEMENT PRACTICES -
Toxicities of 11 metals found in drilling muds to embryos and prezoeae of
the yellow crab have been measured. The distribution of this crab overlaps
significantly with current and planned offshore oil drilling and production
platforms. Lethal concentrations to embryos after 7 days were 1 g/l of iron
or barium (sulfate), two of the most common contaminants. Increased
mortality of embryos resulted from longer exposure. Exposure of embryos to
chromium VI, copper, or zinc actually protected zoeae from those metals,
possibly as a result of induction of biochemical pathways of metal
inactivation.*261*
Management Practices - 1 (DRAFT) - References
Species crab, yellow rock
Species Id M070019
Date 26 AUG 96
References
References - 1