(DRAFT) - Taxonomy
Species clam, Pacific razor
Species Id M060004
Date 26 AUG 96
TAXONOMY
NAME - clam, Pacific razor
OTHER COMMON NAMES - Pacific razor clam
ELEMENT CODE -
CATEGORY - Aquatic Molluscs
PHYLUM AND SUBPHYLUM - Mollusca,
CLASS AND SUBCLASS - Bivalvia,
ORDER AND SUBORDER - Veneroida,
FAMILY AND SUBFAMILY - Solenidae,
GENUS AND SUBGENUS - Siliqua,
SPECIES AND SSP - patula,
SCIENTIFIC NAME - Siliqua patula
AUTHORITY - Dixon, 1789
TAXONOMY REFERENCES - 186
COMMENTS ON TAXONOMY -
Other common names include northern razor clam *13*.
Taxonomy - 1 (DRAFT) - Status
Species clam, Pacific razor
Species Id M060004
Date 26 AUG 96
STATUS
Coded Status
Commercial/consumption
Commercial/bait
REFERENCES FOR STATUS - 13
COMMENTS ON STATUS -
This species has been harvested commercially since the late 1800's and early
1900's. Today only the Willapa Bay spits and the Quinault Indian
Reservation maintain commercial fisheries. The recreational take now far
exceeds the commercial take. Most commercially harvested razor clams now go
to the fresh clam market or are used as crab bait. Razor clams are dug
recreationally throughout the Pacific Northwest *13*.
Status - 1 (DRAFT) - Distribution
Species clam, Pacific razor
Species Id M060004
Date 26 AUG 96
DISTRIBUTION
Distribution - 1 HABITAT ASSOCIATIONS
HABITAT - MARINE
REFERENCES FOR HABITAT - 13
LAND USE -
Barren Land
Beaches
REFERENCES FOR LAND USE - 13
NATIONAL WETLAND INVENTORY CODES
NWI NWICLS NWIMOD NWISPEC
Marine BB. N
Marine, intertidal BB1 N
REFERENCES FOR NWI - 13
COMMENTS ON HABITAT ASSOCIATIONS -
This species is found on open sandy beaches. The sand is usually fine
grained with gentle slopes which help to retain water between tides. The
beaches has a hard surface and a quicksand subsurface texture containing
little organic matter. They will not grow in sheltered bays probably due to
the lack of oxygen renewal and siltation. Ammonium excretion by dense
populations of razor clams could play a significant role in overall nitrogen
cycles of the surf environment *13*.
ANIMAL/PLANT SPECIES ASSOCIATIONS -
Malacobdella grossa
Pinnixa sp.
REFERENCES FOR SPECIES ASSOCIATIONS - 13
Habitat Associations - 1 (DRAFT) - Food Habits
Species clam, Pacific razor
Species Id M060004
Date 26 AUG 96
FOOD HABITS
TROPHIC LEVEL -
FILTER FEEDER
REFERENCES FOR TROPHIC LEVEL - 13
LIFESTAGE FOOD FOOD PART
General Microorganisms Not Applicable
REFERENCES FOR GENERAL FOOD - 13
COMMENTS ON FOOD -
Chaetoceros armarum was identified as the principal food organism available
to this species from October to April. They may comprise 80-100% of the diet
of the razor clam. Several other diatomns are available to a lesser extent
including Asterionella socialis. In the laboratory they have been fed
Pseudoisochrysis paradoxa *13*.
Food Habits - 1 (DRAFT) - Environment Associations
Species clam, Pacific razor
Species Id M060004
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 Air Temperature: Specified in Comments
G Water Temperature: Specified in Comments
G Substrate: Sand
G Relation to Substrate: Occurs in substrate [penetrating]
G Bottom Type [Aquatic]: Sand
G Gradient: Low
G Elevation: Below sea level
G Elevation: 0-100 ft.
G Soil Needs: Sand
G Soil Texture: Fine
G Soil Drainage: Imperfectly and poorly drained
G Soil Moisture: Wet
G Soil Compaction: Easily penetrated
G Terrestrial Features: Bare ground
G Coastal Features: Sand beaches
G Wave intensity: specified in comments
G Estuarine habitat zone: bay
REFERENCES FOR ENVIRONMENTAL ASSOC_ - 13
COMMENTS ON ENVIRONMENTAL ASSOCIATIONS -
The LD50 for this species appears to range from 22.5 degrees C for clams
exposed 4 hours to 27.5 degrees C for clams exposed 1 hour to warmed sea
water. The air temperature near the study site reached 23-29 degrees C
during low tides. On Washington beaches there seems to be a critical
spawning temperature of 13 degrees C although other factors such as tide
cycle and food availability may also play a role. Clams that live
reletively high on the beach may be killed by heavy rains that reduce the
salinity. Slow growth rates are noted in areas with reletively lower
salinity. Razor clams will not live where aeration of the water is limited.
They prefer fine grain sands and gentle slopes that aid in holding water in
the sand between tides *13*.
Environment Associations - 1 (DRAFT) - Life History
Species clam, Pacific razor
Species Id M060004
Date 26 AUG 96
LIFE HISTORY
Physical description: This species has elongate shells that are thin, flat
and smooth. They are covered with a heavy, glossy yellowish periostracum,
with a prominent rib extending from the umbo to the margin on the inside of
the valve. The foot is large and powerful, never pigmented. The syphons are
rather short and united except at the tips. Umbos are nearer the anterior
than posterior end. This species attains a length of seven inches. It
differs from similar clams by having a heavy raised rib extending from the
umbo to the margin of the shell on the inside. This species is reletively
nonpigmented. Razor clams that have never spawned have a translucent
appearance. Once spawning occurs the shells become very dark *13*.
Reproduction: In the Pacific Northwest, this species usually spawns in late
spring or early summer. The season gets progressively later at more northern
locations. In some populations a second, smaller, spawning peak may occur in
late summer or early fall. Some spawning may take place throughout the year.
The eggs and sperm are broadcast into the water where fertilization occurs.
Just prior to spawning the eggs are granular and the sperm are very milky.
The free-floating eggs are pear shaped with a white spot in the center.
Veligers were formed within 10 days at 11-15 degrees C, and by three weeks
they had taken a common clam shape. At five weeks a foot had formed although
the entire animal is still transparent. At eight weeks the velum is gone and
the shell begins to elongate. Setting occured at about 10 weeks. The egg
diameter averaged slightly over 90 mm. Movement of the larvae may be at
least several miles. Maturation is more closely linked with size than age.
Maturity is commonly reached at about 10 cm. The age at maturity is about 2
years in the Pacific Northwest and 3-4 years in Alaska. Maturation is
slowest during the winter and increases as water temperatures rise in the
spring *13*. Behavior: There are substantial numbers of subtidal juveniles
up to 550 yards offshore and at depths of about 11 meters. Densities of
setting juveniles may approach 1500/sq foot on the Washington coast. As the
juveniles set, they dig into the sand. The young clams have been noted to
move laterally along the surface of the sand as far as 30 cm which may
result in a limited amount of redistribution of juveniles after setting.
Once established the juveniles remain in place in the upper few inches of
sand. Adult razor clams are usually about one foot beneath the surface of
the sand and show no laveral movement. However, they do show rapid vertical
mobility with movement rates of 9 inches to 1 foot per minute. One clam was
observed digging to a depth of 4 feet 9 inches. When burrowing, the foot is
extended down into the sand where it hydraulically expands to serve as an
anchor. The muscles then contract to pull the clam downward. These clams are
densest in the lower intertidal zone although subtidal populations may also
be large. A band of adult clams was reported along the Oregon coast to 8
feet with less densely packed clams at depths of at least 20 feet. Some feel
that offshore clam populations are considered brood stock for intertidal
populations. The principal food of this species is Chaetoceros armatum
although several other diatoms are used to a lesser extent including
Asterionella socialis. They have been fed the dinoflagellate
Pseudoisochrysis paradoxa in laboratory aquaria *13*. Population parameters:
The sex ratio is 1:1. Sexual maturity is reached at about 10 cm, or 2 years
in the Pacific Northwest and 3-4 years in Alaska. The maximum age is five
years in Pismo Beach, 9-11 years in the Pacific Northwest, and 18-19 years
in Alaska. Fecundity is 6-10 million eggs on Pacific Northwest beaches and
Life History - 1 (DRAFT) - Life History
Species clam, Pacific razor
Species Id M060004
Date 26 AUG 96
more than 118 million on Alaskan beaches *13*. Limiting factors: Heavy sets
may lead to reduced growth and increased mortality in the current year class
and reduced growth in established adults. They are limited to high energy
sand beaches that are not sheltered. The LD50 appears to range from 22.5
degrees C for clams exposed 4 hours to 27.5 degrees C for clams exposed 1
hour to warmed seawater. A major cause of mortality for young razor clam is
the scouring effect of winter storms. Clams that live reletively high on the
each may be killed by heavy rains which reduce salinity. Nuclear inclusion X
(NIX) a prokaryotic pathogen caused the complete closure of the razor clam
fishery in Washington State in 1984. There has been no validated record of
paralytic shellfish poisoning reported for this species *13*. Aquatic
terrestrial associations: This species is preyed on by seagulls, the
northwestern crow sandpipers, glaucous-winged gulls, sea ducks, scooters,
Dungeness crabs and green and white sturgeon. beaches in the Pacific
Northwest, and up to 118 million in Alaska *13*.
REFERENCES FOR LIFE HISTORY- 13
Life History - 2 (DRAFT) - Management Practices
Species clam, Pacific razor
Species Id M060004
Date 26 AUG 96
MANAGEMENT PRACTICES
RESULT MANAGEMENT PRACTICE
Beneficial Regulating harvest of species being described
Beneficial Restricting/regulating human use of habitats
Beneficial Regulating harvest - setting size limits
REFERENCES FOR BENEFICIAL MANAGEMENT PRACTICES - 13
COMMENTS ON MANAGEMENT PRACTICES -
Because improperly replanted razor clams are unlikely to survive, bag limits
now carry a stipulation that all razor clams, reguardless of size or
condition, must be kept and counted toward the daily bag *13*.
Management Practices - 1 (DRAFT) - References
Species clam, Pacific razor
Species Id M060004
Date 26 AUG 96
References
13 Lassuy, D. R., and D. Simons. 1989. Species profiles: life
histories and environmental requirements of coastal fishes and
invertebrates (Pacific Northwest)--Pacific razor clam. U.S.
Fish. Wildl. Serv. Biol. Rep.82(11.89). U.S. Army Corps of
Engineers, TR-EL-82-4. 16pp.
References - 1