(DRAFT) - Taxonomy
Species clam, surf
Species Id M060001
Date 26 AUG 96
TAXONOMY
NAME - clam, surf
OTHER COMMON NAMES -
ELEMENT CODE -
CATEGORY - Aquatic Molluscs
PHYLUM AND SUBPHYLUM - ,
CLASS AND SUBCLASS - Bivalvia,
ORDER AND SUBORDER - Veneroida,
FAMILY AND SUBFAMILY - Mactridae,
GENUS AND SUBGENUS - Spisula,
SPECIES AND SSP - solidissima,
SCIENTIFIC NAME - Spisula solidissima
AUTHORITY -
TAXONOMY REFERENCES - 53
COMMENTS ON TAXONOMY -
Other common names....Bar clam (Canada), hen clam (Maine), sea clam
(Massachusetts), beach clam, skimmer clam (Ropes 1980).*53*
Taxonomy - 1 (DRAFT) - Status
Species clam, surf
Species Id M060001
Date 26 AUG 96
STATUS
Coded Status
Commercial
Commercial/consumption
Existing, FMP exists
REFERENCES FOR STATUS - 53
COMMENTS ON STATUS -
After passage of the Fishery Conservation and Management Act of 1976, a
fishery Management Plan (FMP) was developed for surf clam stocks in the U.S.
Fishery Conservation Zone. At the time this FMP was developed, surf clam
stocks were at a relatively low level compared to historical stocks.
Intensive fishing during the 1960's and early 1970's and the oxygen
depletion dieoff in New Jersey waters in 1976 reduced exploitable surf clam
stocks. To achieve the catch goals in the FMP, various regulatory
mechanisms have been implemented, including annual and quarterly landings
quotas, weekly effort restrictions, a moratorium on new vessel construction,
closure of specific areas to protect young clams (future recruitment), and
most recently (26 July 1981) a minimum clam size of 14 cm (5.5 inches).
Since its adoption, the minimum size limit has resulted in the further
decline of catch per unit effort, thus indicating the importance of 10- to
13cm (3.9- to 5.1-inch) clams to the fishery prior to size regulation.*53*
Status - 1 (DRAFT) - Distribution
Species clam, surf
Species Id M060001
Date 26 AUG 96
DISTRIBUTION
Distribution - 1 HABITAT ASSOCIATIONS
NATIONAL WETLAND INVENTORY CODES
NWI NWICLS NWIMOD NWISPEC
Marine UB1
Marine BB2
Marine UB2
Marine UB1
Marine BB2
Marine UB2
REFERENCES FOR NWI - 53
COMMENTS ON HABITAT ASSOCIATIONS -
Surf clams were a dominant species collected in surveys of inshore benthic
fauna from southwestern Long Island, New York, and Little Egg Harbor, New
Jersey. Most surf clam beds of the Middle Atlantic Bight are located from
the beach zone to a depth of 43.9 m (144 ft) off Long Island, out to 59.7 m
(196 ft) off New Jersey, from 10.1m to 65.5 m (33 ft to 215 ft) off the
Delmarva Peninsula, and from 8.2 m to 58.8 m (27 ft to 193 ft) off Virginia
and North Carolina. Inshore distribution of surf clams, particularly in
estuarine zones, is probably limited by salinity requirements. Minimum
salinities for larval and adult surf clam survival were 16 ppt and 12.5
ppt, respectively. Adult surf clams tolerated salinities from 14 pt to 52
ppt (concentrated seawater).*53*
Habitat Associations - 1 (DRAFT) - Food Habits
Species clam, surf
Species Id M060001
Date 26 AUG 96
FOOD HABITS
TROPHIC LEVEL -
FILTERER
REFERENCES FOR TROPHIC LEVEL - 53
LIFESTAGE FOOD FOOD PART
Larva See Comments; Food
Adult Bacillariophyceae Not Specified
Adult See Comments; Food
REFERENCES FOR GENERAL FOOD - 53
REFERENCES FOR ADULT FOOD - 53
REFERENCES FOR LARVAE FOOD - 53
COMMENTS ON FOOD -
Like many bivalves, surf clams are planktivorous, siphon feeders. Feeding
activity of surf clams is intimately associated with the overall process of
siphoning water for respiration and excretion. Feeding surf clams burrow
deep enough in the substrate so that the end of the incurrent siphon barely
protrudes above the bottom. Some sand grains and other unwanted material may
be ingested under these circumstances, but the action of papillae fringing
the siphon may reduce such occurrences. Surf clams in the breaker zones of
coastal oceanic habitats close their siphons when breaking waves with
suspended sand pass by, reopening the siphon quickly after the wave passes.
Food particles trapped on mucus-coated inner siphonal surfaces move
unidirectionally with the mucus toward the gut of the clam. The crystalline
style in the digestive tract stirs the stomach contents and aids in
producing and excreting enzymes for digestion. Studies have been conducted
on the enzymes and enzymatic processes in the surf clam gut and on the
neurophysiological mechanisms of gut movements.*53*
COMMENTS ON ADULT FOOD -
Stomachs of adult surf clams from New Jersey coastal waters contained a
variety of diatom genera and species, but only Amphipora consticta and
Tintinnus spp. were identified from the contents. Difficulties in
identification were caused by change in diatom structure after entry into
the surf clam's digestive tract.*53*
COMMENTS ON LARVAE FOOD -
In laboratory-reared surf clam larvae, yolk material was fully absorbed and
algal cells began appearing in some stomachs at 1 day of age (veliger
larvae). Larval surf clams fed on algal cells throughout the remainder of
the stage. Loosanoff and Davis successfully reared larval surf clams on
mixed plankton cultures and discussed conditions necessary for raising
larval surf clams in relation to food. Laster and Strittmater noted that
maltase activity in developing larval surf clams increased tenfold in the
early veliger stage, coincidental with development of the esophagus,
stomach, intestine, and digestive gland.*53*
Food Habits - 1 (DRAFT) - Environment Associations
Species clam, surf
Species Id M060001
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
L Water Temperature: Between 15-21 degrees C
L
L
L Water Temperature: Between 21-27 degrees C
J Water Temperature: Greater than 27 degrees C
J Water Temperature: Between 21-27 degrees C
J Water Temperature: Between 15-21 degrees C
J Water Temperature: Below 15 degrees C
J Water Temperature: Specified in Comments
A Air Temperature: Specified in Comments
A Water Temperature: Between 21-27 degrees C
A Water Temperature: Between 15-21 degrees C
A Water Temperature: Below 15 degrees C
A
A
A
A
A
REFERENCES FOR RESTING ADULT ENVIRONMENTAL ASSOC_ - 53
REFERENCES FOR RESTING JUVENILE ENVIRONMENTAL ASSOC_ - 53
REFERENCES FOR RESTING LARVAE ENVIRONMENTAL ASSOC_ - 53
COMMENTS ON ENVIRONMENTAL ASSOCIATIONS -
In laboratory experiments, the burrowing rate of surf clams increased as
water temperature increased to 20 degrees C, but decreased above this
temperature. Some clams failed to begin digging activities at water
temperatures below 2 degrees C, and others began digging but could not
accomplish complete burial at that temperature. Temperature shocks induced
by a 14 degrees C (25 degrees F) increase in water temperature, with a
starting temperature of 4 degrees C (39 degrees F), did not significantly
affect burrowing. A temperature increase of 22 degrees C (40 degrees F)
produced gaping, lethargy, and eventually death. Water temperature is also
important for initiation and rate of gonadal development (Loosanoff and
Davis 1963), and for initiation and timing of spawning (Ropes 1968b).*53*
Environment Associations - 1 (DRAFT) - Environment Associations
Species clam, surf
Species Id M060001
Date 26 AUG 96
COMMENTS ON RESTING ADULT ENVIRONMENTAL ASSOC_ -
Survival of spawning adults and their fertilized eggs was significantly
affected at water temperatures of 30 degrees C (86 degrees F) or higher.
Adult surf clams were unable to establish pedal anchorage at water
temperatures greater than 30 degrees C (86 degrees F). Lethally low water
temperatures for adult surf clams are probably never reached in their
oceanic habitat, but low air temperatures (less than 0 degrees C or 32
degrees F) may freeze exposed gill tissue in live clams temporarily washed
up onto the beach during storms.*53*
Minimum salinity for adult surf clam survival was 12.5 ppt. Adult surf
clams tolerated salinities from 14 ppt to 52 ppt (concentrated seawater).
Encroachment of surf clams into estuarine areas is probably limited by
salinity.*53*
COMMENTS ON RESTING JUVENILE ENVIRONMENTAL ASSOC_ -
Juvenile surf clams survived higher temperatures than adults, but became
inactive at 4 degrees C (39 degrees F) or lower.*53*
COMMENTS ON RESTING LARVAE ENVIRONMENTAL ASSOC_ -
Surf clam larvae tolerated a water temperature range from 14 degrees C to
30 degrees C (57 degrees F to 86 degrees F). Optimum temperature for
larval development was 22 degrees C.*53*
Minimum salinity for larval surf clam survival was 16 ppt.*53*
Environment Associations - 2 (DRAFT) - Life History
Species clam, surf
Species Id M060001
Date 26 AUG 96
LIFE HISTORY
PHYSICAL DESCRIPTION:
Shells moderately strong, somewhat triangular. Hinge with distinct cuplike
chondrophore and strong lateral teeth crenulated on inner side, visible with
hand lens even in very small - 3/8 in. (9mm) - specimens. Outside nearly
smooth, fresh shells have yellowish-olive periostracum. To 8 in.
(200mm).*177*
REPRODUCTION:
Surf clams spawn from June through mid-August; the peak season varies with
latitude. In some areas, a second spawning period may occur from
mid-October through early December. Fertilized eggs probably stay at or
near the bottom and the free swimming and crawling larvae metamorphose in a
month or less into the burrowing form. Optimum temperature range for
development of the larvae lies in the 57 degrees - 68 degrees F range
(NMFS, 1974).*138*
Surf clam populations from New Jersey coastal waters exhibited two annual
spawnings in 1962, 1963, and 1964. These occurred from mid-July to early
August and from mid-October to early November. In 1965, a single spawning
period from mid-September to mid-October was observed. The spawning season
is probably earlier south of New Jersay, since juvenile clams have been
found in North Carolina waters in April, May, and June. Little is known
concerning the spawning season of surf clam populations north of New York.
Within a bed of clams, spawning is probably a synchronous, annual event.
Water temperature is an important factor influencing initiation and time of
spawning, and may also influence rate of gonadal ripening and number of
major spawning periods per year. After eggs and sperm are broadcast,
fertilization occurs in the water column above the spawning bed of
clams.*53*
BEHAVIOR:
Eggs. Surf clam eggs are spherical and average 1.42 mm (0.06 inch) in
diameter across the vitelline membrane; the inner germinal vesicle averages
0.79 mm (0.03 inch) in diameter. Several layers lie between the invisible,
outer, jellylike layer and the germinal vesicle.
Little is known concerning the effects of water temperatures on development
rate of surf clam eggs. Fertilized eggs held at an average water
temperature of 21.7 degrees C (71 degrees F) (range 18.3 degrees to 24.9
degrees C or 65 degrees to 77 degrees F) in the laboratory completed first
cleavage by 70 min after fertilization. Trochophore larvae began appearing
9 hr after fertilization. Fertilized eggs reached the veliger larvae stage
in 72 hr at 14 degrees C (57 degrees F), and in 28 hr at 22 degrees C (72
degrees F).*53*
Larval Stage. Pyramid-shaped, planktonic trochophore larvae began
developing from swimming gastrulae 9 hr after fertilization at a water
Life History - 1 (DRAFT) - Life History
Species clam, surf
Species Id M060001
Date 26 AUG 96
temperature of 21.7 degrees C. Veliger larvae (first appearance of bivalved
shell) formed by 19 to 20 hr after fertilization, and a ciliated velum also
appeared at this time. The velum is used for propulsion of the larvae until
the juvenile or "settlement" phase is reached.
Pediveliger larvae, a transitional, "swimming-crawling" larval stage with
development of a foot for burrowing, were first observed 18 days after
fertilization at 21.7 degrees C; by 21 days, nearly all veliger larvae had
developed through the brief pediveliger stage and metamorphosed into
juvenle clams (complete absorption of velum, settlement to the substrate,
and beginning of sedentary life stage).
Water currents in areas where planktonic surf clam larvae live are important
in determining eventual patterns of distribution and settlement for
developing juveniles. Dispersal and redistribution of surf clams to other
areas, through swimming and crawling activities and water currents, occur
primarily during the larval stages. Specific information, however, on the
interaction of water currents and larval settlement patterns is
unavailable.*53*
Juvenile Stage. Juvenile surf clams, with a well-developed foot for
burrowing and fully absorbed velum, were present 18 days after fertilization
at 21.7 degrees C. By 21 days, all clam larvae had metamorphosed into
juveniles. The juvenile stage lasts from first settlement in the substrate
until sexual maturity, which may occur during the second (age 1+) or third
(age 2+) summer of life.
The extent of juvenile surf clam movement is a locomotion called "leaping"
(a push with the foot against the substrate). A young surf clam, disturbed
from its burrow by the investigators or a predator, usually reburrowed in
the same spot. Leaping was infrequent, and was usually caused by repeated
disturbance of the clam in its burrow. Stimuli reported for leaping in a
closely related mactrid, Mactra corallina, were (1) proximity to a predator,
(2) inability to burrow in the substrate of settlement, and (3) exposure to
air. Researchers concluded that surf clam leaping was exceptional and
infrequent, and probably insignificant in determining their overall
settlement and distribution patterns. Voluntary leaping (i.e., with no
disturbance) was never observed.*53*
Adult Stage. Adult surf clams spend most of their lives burrowed in medium
to coarse sand and gravel substrates. Since siphons are about as long as
the adult clam, burial depth may be well below the substrate surface.
Papillae fringing the siphonal openings may aid in preventing sand grains
from being drawn into the siphon during respiration and feeding. Abundance
of adults in suitable substrates ranges from loose, fairly evenly
distributed aggregations to localized or patchy, dense beds, occasionally
with individuals close enough in the substrate for shells to touch.
Surf clams were a dominant species collected in surveys of inshore benthic
fauna from southwestern Long Island, New York, and Little Egg Harbor, New
Jersey. Most surf clam beds of the Middle Atlantic Bight are located from
the beach zone to a depth of 144 ft off Long Island, out to 196 ft off New
Jersey, from 33 to 215 ft off the Delmarva Peninsula, and from 27 to 193 ft
Life History - 2 (DRAFT) - Life History
Species clam, surf
Species Id M060001
Date 26 AUG 96
off Virginia and North Carolina. Inshore distribution of surf clams,
particularly in estuarine zones, is probably limited by salinity
requirements. Minimum salinities for larval and adult surf clam survival
were 16 ppt and 12.5 ppt, respectively. Adult surf clams tolerated
salinities from 14 ppt to 52 ppt (concentrated seawater).
Adult surf clams rarely voluntarily vacate their burrows, and under natural
stimuli alone, may live their entire lives in a single burrow. Researchers
reported little or no voluntary movement of marked clams under natural
conditions. Oceanic storms and water currents generated over the ocean
floor may displace surf clams a considerable distance, but survivors of the
displacement not washed onto the beach probably burrow at or near the site
where they settle after a storm.*53*
LIMITING FACTORS:
Predators. Little is known concerning the predators of planktonic surf clam
larvae or newly settled juveniles. Some information on predators of other
young mactrid clams in European waters is available, but its relevance and
applicability to Atlantic coast surf clam populations are unknown.
The most important predators on adult surf clams are two moon snail species,
Lunatia heros and Polinices duplicatus. A characteristic countersunk hole
drilled by the snail's radula is usually located near the hinge or umbo of
the shell. Low temperatures and salinities apparently reduce
predation rates of these snails. In laboratory experiments P. duplicatus
ceased feeding at 5 degrees C or lower and 6 ppt salinity, while L. heros
reduced feeding at 2 degrees C or lower and ceased feeding below 10 ppt
salinity. Lunatia heros may be a size-selective predator on surf clams,
since most surf clams selected by snails off Long Island were less than 80
mm in shell length. This selection, however, may also be related to
seasonal or geographic availability of clam size classes to predators.
Another invertebrate predator of the surf clam is the boring snail,
Urosalpinx cinerea. In laboratory experiments this snail was unable to bore
successfully in running seawater, but was much more effective at boring surf
clam shells in standing seawater.
Predatory fish reported to consume surf clams are haddock (Melanogrammus
aeglefinus) and cod. Much of this apparent predation may result from
scavenging on the soft bodies of fractured surf clam shells which result
from major oceanic storms. Recreational cod and haddock fishermen believe
that surf clam soft bodies are one of the best baits for several days after
a major oceanic storm, but are only fair baits at other times.*53*
Competitors. Little is known concerning competitive interactions between
surf clams and other benthic organisms. If competition occurs, it probably
involves availability of space at the appropriate depth in the substrate and
availability of usable food organisms in the water column just above the
seabed.
Some evidence exists for intraspecific competition in dense, inshore surf
clam beds, including roughened shell surfaces and edges, older shell
Life History - 3 (DRAFT) - Life History
Species clam, surf
Species Id M060001
Date 26 AUG 96
deposits raised one on top of another like shingles, and blunted posterior
ends of shells. These features are generally unique to dense populations
and may indicate disruption in growth patterns through some competition
among clams for space or food. In laboratory experiments, localized,
physical stimulation of the mantle edge of some mollusks produced large
areas of shell regeneration, indicating that proximity of individual clams
in dense beds may account for the irregularities in shell growth observed in
such beds.*53*
POPULATION ATTRIBUTES:
Growth. Prior to 1975, most determinations of age and growth of adult surf
clams were made by counting and measuring radii of concentric "rings" or
"ridges" commonly observed on the external surface of shells. Age and
growth techniques were refined by National Marine Fisheries Service
investigators beginning in 1975. Shells cut along a line from the umbo to
the ventral edge and polished revealed distinctive marks related to the
external ridges. Greater accuracy in measuring age and growth was achieved
because the marks were better defined than the external ridges. Since
development of this technique, studies have shown age-size relationships
using cut and polished shells. Researchers using this new technique found
that surf clams sampled from the Ocean City area grew faster and lived
longer than those collected from Barnegat Bay and Point Pleasant areas. But
it was noted that these differences may be a function of depth of the clam
bed and its location with respect to shore (i.e., inshore vs. offshore).
Researchers found that surf clams sampled from relatively deepwater,
offshore areas (18.3 to 28.0 m or 60 ft to 92 ft deep) grew faster and lived
longer than those sampled from relativley shallow-water, inshore sites (11.6
m to 15.0 m or 38 ft to 49 ft). The influence, however, of exploitation
differences among these populations was not considered.
The most recently developed technique for aging surf clams is
thin-sectioning of the chondrophore (located in the hinge of the clam).
Marks on the sectioned chondrophore correspond to those on the cut and
polished shell. This method was apparently simpler to use and data on
growth easier to collect compared to the valve-cutting technique.*53*
Longevity. Determinations of surf clam longevity have been made from
individual specimens. Three records of the oldest surf clams are 17-year-old
specimens averaging 163 mm (6.41 inches) long, 20-year-old specimens
averaging 147 mm (6.46 inches) and 25-year-old specimens averaging 164 mm.
The greatest shell length ever reported for surf clams was a 226-mm
(8.9-inch) specimen collected offshore of Point Pleasant, New Jersey, at a
depth of 21.3 m (70 ft). This individual was in a commercial sample of 10,
averaging 193 mm (7.6 inches) and ranging from 178 to 226 mm (7.0 to 8.9
inches) in length.*53*
Sex ratios. A 4-year study of the reproductive cycle of surf clams off the
New Jersey coast, between 1962 and 1965, indicated that sex ratios in clam
beds did not deviate significantly from a 1:1 ratio. Data from National
Marine Fisheries Service (NMFS) surveys during 1965 and miscellaneous
sources also indicated no significant deviation from a 1:1 sex ratio in the
populations sampled.*53*
Life History - 4 (DRAFT) - Life History
Species clam, surf
Species Id M060001
Date 26 AUG 96
Recruitment and production. In three unexploited surf clam beds in the Gulf
of St. Lawrence, off Buctouche, New Brunswick, density of surf clams
averaged 1.06/m(squared) and ranged from 0.68 to 1.25/m(squared). Total
estimated standing crop in these three beds, which collectively covered 2.6
km(squared), was 2.8 million clams. Three models for predicting yield based
on varying fishing mortality rate (F) and age of first capture were tested
by using data from these unexploited beds. To develop and test these models,
natural mortality rate (M) was assumed equal to 0.2 (estimated with catch
curves from diving expeditions), and recruitment was assumed constant at
500,000 age 1 clams per year to an initial population size of 2.8 million
clams. Values for variables in the three yield models were (1) age at first
capture 5 years (approximately 8.0 cm or 3.1 inches) and F=0.5, (2) age at
first capture 3 years (approximately 4.0 cm or 1.6 inches) and F=0.5, and
(3) age at first capture 3 years and F=0.25.
For all three models, catch rates declined steadily from the first year of
fishing through the eighth year. Long-term yield per recruit was 40% higher
for model (1) compared to model (2). Model (1) approximated an optimum
sustained yield per recuit. Initial catch under model (2) was half that of
the other models, but long-term catch under model (2) was intermediate to
models (1) and (3). Although model (1) appeared to be near optimum for
long-term sustained yield, model (3) was predicted to have the highest catch
per unit effort (kg per diver hour); and model (1) would require twice the
fishing effort of model (3) to achieve the long-term predicted yield.
Researchers also noted that fishing mortality rates higher than 0.5 or age
of first capture greater than 5 years significantly decreased yield per
recruit compared to the three models tested (this was apparently determined
in preliminary model testing).*53*
LIFE HISTORY CODES -
Dispersion: Clumped
Nest/Den Site: Underwater burrow
REFERENCES FOR LIFE HISTORY- 53
Life History - 5 (DRAFT) - Management Practices
Species clam, surf
Species Id M060001
Date 26 AUG 96
MANAGEMENT PRACTICES
RESULT MANAGEMENT PRACTICE
Existing Regulating harvest of species being described
Existing Restricting/regulating human use of habitats
Existing Regulating harvest - setting size limits
Existing Regulating commercial harvest gear types
REFERENCES FOR EXISTING MANAGEMENT PRACTICES - 53
COMMENTS ON MANAGEMENT PRACTICES -
After passage of the Fishery Conservation and Management Act of 1976, a
fishery Management Plan (FMP) was developed for surf clam stocks in the U.S.
Fishery Conservation Zone. At the time this FMP was developed, surf clam
stocks were at a relatively low level compared to historical stocks.
Intensive fishing during the 1960's and early 1970's and the oxygen
depletion dieoff in New Jersey waters in 1976 reduced exploitable surf clam
stocks. To achieve the catch goals in the FMP, various regulatory
mechanisms have been implemented, including annual and quarterly landings
quotas, weekly effort restrictions, a moratorium on new vessel construction,
closure of specific areas to protect young clams (future recruitment), and
most recently (26 July 1981) a minimum clam size of 14 cm (5.5 inches).
Since its adoption, the minimum size limit has resulted in the further
decline of catch per unit effort, thus indicating the importance of 10- to
13cm (3.9- to 5.1-inch) clams to the fishery prior to size regulation.*53*
Management Practices - 1 (DRAFT) - References
Species clam, surf
Species Id M060001
Date 26 AUG 96
References
53* Fay, C., R. Neves, G. Pardue. 1983. Species Profiles: Life
Histories and Environmental Requirements of Coastal Fishes and
Invertebrates (Mid-Atlantic) -- Surf Clam. U.S. Fish and
Wildlife Service Biol. Rep. 82(11.13) pp 23.
177* Gosner, K.L. 1978. A Field Guide to the Atlantic Seashore:
Invertebrates and Seaweeds of the Atlantic Coast from the Bay of
Fundy to Cape Hatteras. The Peterson Field Guide Series.
Houghton Mifflin Company Boston, MA:329.
138* Gusey, W. F. 1978. The Fish and Wildlife Resources of the Middle
Atlantic Bight. Shell Oil Company Houston, TX pp 582.
References - 1