REFERENCECOPY 

Do Not Remove from the Librarv 

U. S. Fish and Wildlife Service 

National Wetlands Research Center 

- 

FWSIOBS-82111.13 /OtKajun V 'TR EL-82-4 

October 1983 Lafayette, Louisiana 70506 

Species Profiles: Life Histories and 

Environmental Requirements of Coastal Fishes and 

Invertebrates (Mid-Atlantic) 

SURF CLAM 

Fish and Wildlife Service 

Coastal Ecology Group 

Waterwavs Ex~eriment Station 

U.S. Department of the Interior U.S. Army Corps of Engineers 
FWS/OBS-82111.13 

TR EL-82-4 

October 1983 

Species Profi 1 es: Life Histories and Environmental Requirements 

of Coastal Fishes and Invertebrates (Mid-At1 antic) 

SURF CLAM 

Clemon W. Fay, Richard J. Neves, and Garland B. Pardue 

Department of Fisheries and W i 1 dl i fe Sciences 

Virginia Polytechnic Institute and State University 

Blacksburg, VA 24061 

Project Manager 

Larry Shanks 

Project Officer 

Norman Benson 

National Coastal Ecosystems Team 

U.S. Fish and Wildlife Service 

1010 Gause Boulevard 

Sl idell, LA 70458 

This study was conducted 

in cooperation with 

Coastal Ecology Group 

U.S. Army Corps of Engineers 

Waterways Experiment Station 

Performed for 

National Coastal Ecosystems Team 

Division of Biological Services 

Fish and Wildlife Service 

U.S. Department of the Interior 

Washington, DC 20240 
CONVERSION FACTORS 

Metric -- to U.S. Customary 

Multiply - To Obtain 

mi 11 imeters (mm) 

centimeters (cm) 

rneters (m) 

kilometers (km) 

i nc hes 

i nc hes 

feet 

miles 

square meters (m2) 

square kilometers (km2) 

hectares (ha) 

square feet 

square miles 

acres 

liters (1) 

cubic rneters (m3) 

cubic meters 

gal 1 ons 

cubic feet 

acre-feet 

mi 11 i grams (mg) 

grarns (gm) 

ki 1 ograms (kg) 

metric tons (mt) 

metric tons (mt) 

kilocalories (kcal ) 

ounces 

ounces 

pounds 

pounds 

short tons 

BTU 

Celsius degrees Fahrenheit degrees 

U.S. Customary to Metric 

inches 

inches 

feet (ft) 

fathoms 

miles (mi) 

nautical miles (nmi) 

millimeters 

centimeters 

meters 

meters 

kilometers 

ki 1 ometers 

square feet (ft2) 

acres 

square miles (mi 2, 

square meters 

hectares 

square kilometers 

gallons (gal) 

cubic feet (ft3) 

acre-feet 

1 i ters 

cubic meters 

cubic meters 

ounces (02) 

pounds (Ib) 

short tons (ton) 

BTU 

grams 

kilograms 

metric tons 

kilocalories 

Fahrenheit degrees Cel s i us degrees 
CONTENTS 

Page 

CONVERSIONTABLE ............................. PREFACE ................................. ACKNOWLEDGPlENTS .............................. 

NOMENCLATLlRE/TAXONOMV/RANGE ....................... MORPHOLOGY/IDENTIFICATION AIDS ...................... REASON FOR INCLUSIOIV IN SERIES ...................... LIFE HISTORY ............................... Reproductive Physiologylstrategy .................... Spawning ................................ Eggs .................................. Larvae ................................. Juveriil es ............................... Adults ................................. GROWTH CHARACTERISTICS .......................... Growth Rates .............................. Length-Weight Relationships ...................... Age-Length/Age-Weight Re1 ationships .................. THE FISHERY ............................... Corgmercial Fisheries .......................... PopulationDyna~nics .......................... ECOLOGICALROLE ............................. Food Habits .............................. Feeding Behavior ............................ Predators ............................... Competitors .............................. ENVIRONMENTAL REQUIREMENTS ........................ Temperature .............................. Sal inity ................................ Di ssol ved Oxygen ............................ Other Environmental Factors ...................... Pollutants ............................... 

LITERATURE CITED ............................. 
PREFACE 

This species profile is one of a series on coastal aquatic organisms, 

principally fish, of sport, commercial, or ecological importance. The profiles 

are designed to pravide coastal managers, engineers, and biologists with a brief 

comprehensive sketch of the biol ogical characteristics and envi ronmental requi re- 

~nents of the species an3 to describe how populations of the species may be 

expected to react to envi ronmental changes caused by coastal development. Each 

profil e has sections on taxonomy, 1 ife history, ecol ogical rol e, environmental 

requiranents, and economic importance, if appl icabl e. A three-ring binder is 

used for this series so that new profiles can be added as they are prepared. 

This project is jointly planned and financed by the U.S. Army Corps of Engineers 

and the U.S. Fish and Wildl ife Service. 

Suggestions or questions regarding this report shoul d be directed to: 

Information Transfer Special ist 

National Coastal Ecosystems Team 

U.S. Fish and Wildlife Service 

NASA-Sl idel 1 Computer Compl ex 

1010 Gause Boul evard 

Sl idel 1 , LA 70458 

U. S. Arrny Engineer Waterways Experiment Station 

Attention: WESER 

Post Office Box 631 

Vicksburg, MS 39180 

This series should be referenced as follows: 

U.S. Fish and Wildl ife Service. 1983. Species profiles: life histories and 

environmental requirements of coastal fishes and invertebrates. IJ. S. Fish 

and Wil dl ife Service, Division of Biological Services, FWS/OBS-82/11. 

U.S. Army Corps of Engineers, TR EL-82-4. 

This profile should be cited as follows: 

Fay, C.W., R.J. Neves, and G.B. Pardue. 1983. Species profiles: 1 ife histories 

and environmental requirements of coastal fishes and invertebrates (MidAtlantic) -- surf clam. U.S. Fish and Wild1 ife Service, Division of 

Biol og ical Services, FWS/OBS-82/11.13. U. S. Army Corps of Engineers, 

TR EL-82-4. 23 pp. 
ACKNOWLEDGMENTS 

We are grateful for the review by Steve Murawski, National Marine Fisheries 

Service, Woods Hole, Massachusetts. 
Figure 1. Surf clam. 

SURF CLAM 

Scientific name.. .... Spisula solidissima 

Preferred common name. ;". ...... Surf 

clam (Figure 1) 

Other common names.. .. Bar clam 

(Canada), hen clam (Maine), sea 

clam (Massachusetts), beach clam, 

skimmer clam (Ropes 1980) 

Class.. ....................... Bivalvia 

Order. ..................... .Veneroida 

Family. ...................... Mactridae 

Geographic range: Gulf of Maine south 

to Cape Hatteras, North Carolina 

(Wigley and Emery 1968) (see 

Figure 2 for the distribution of 

the surf clam in the mid-Atlantic 

reg ion 1 . A much broader 

latitudinal range, from the southern Gulf of St. Lawrence to the 

northern Gulf of Mexico, was 

given in Merrill and Ropes 

(1969), Ropes et al. (1969), and 

Ropes (1980). Evidence that the 

populations south of Cape Hatteras are actually a distinct subspecies of 3. solidissima, S. s. 

ravaenelli, is presented in MerrTll 

and Webster (1964) and Jacobsen 

and Old (1966). Surf clams are 

predominantly oceanic, most common in turbulent waters just 

beyond the breaker zone (Ropes 

1980). Encroachment into estuarine zones is probably limited by 

salinity requirements. 
PHI LADELPHI 

MILES 

KILOMETERS 

Areas of highest abundance 

Areas of high abundance 

Areas of moderate abundance 

Figure 2. Mid-Atlantic distribution of the surf clam, with areas of relative abundance indicated. I 
MORPHOLOGY/IDENTI FICA-TION AIDS 

Shells oval to trigonal, concentrically striated or ridged, otherwise 

with no external sculpture; gape 

slight when shell closed; ligament spisuloid; complete complement of lateral 

teeth; pallial sinus shallow and not 

larger than adductor muscle scar 

(Chamberlin 1954). Detailed family 

and generic morphological cha racteristics and anatomical drawings are given 

in Ropes (1 980) . 

REASON FOR INCLUSION IN SERIES 

The surf clam commercial fishery 

has grown from a small bait fishery 

during the years prior to World War II 

(Ropes et al. 1969) to one contributing 71.8% of all clam meats used in the 

United States between 1970 and 1974 

(Ropes 1982). Per capita consumption 

of surf clam meat doubled between 

1947 and 1974 (Ropes 1982). Within 

the mid-Atlantic region, the surf clam 

is a particularly important commercial 

clam species because of its wide distribution and abundance in the 

region, and because most vessels in 

the fishery are located in New York, 

New Jersey, Delaware, Maryland, and 

Virginia (Ropes 1982). 

LIFE HISTORY 

Reproductive Physiology/Strategy 

Surf clams are heterosexual 

(Ropes 1980), though hermaphroditism 

has been reported (Ropes 1968a). 

Male and female surf clams are identical in external appearance, and histological sectioning and examination of 

gonads is the only sure way to determine surf clam gender (Ropes et al. 

1969). Male and female surf clams 

reach full sexual maturity during their 

second year, even though ripe gonads 

and some spawning activity may occur 

in l-year-old clams (Ropes 1979). 

Smallest reported shell length at 

maturity was 45 mm (1.8 inches) 

(Ropes 1980). No observations on 

fecundity of surf clams are available. 

Spawning 

Surf clam populations from New 

Jersey coastal waters exhibited two 

annual spawnings in 1962, 1963, and 

1964 (Ropes 1968b). 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 Jersey, since juvenile clams have been 

found in North Carolina waters in 

April, May, and June (Williams and 

Porter 1971). 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 (Ropes 1968b). Water temperature is an important factor influencing 

initiation and time of spawning (Ropes 

1980), and may also influence rate of 

gonadal ripening and number of major 

spawning periods per year (Ropes 

1968b). After eggs and sperm are 

broadcast, fertilization occurs in the 

water column above the spawning bed 

of clams (Murawski and Serchuk 1981; 

Ropes 1980). 

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 (Allen 

1953). Several layers lie between the 

invisible, outer, jellylike layer and 

the germinal vesicle (Ropes 1980). 

Longo (1973) reviewed the literature 

on embryogenesis of fertilized #urf 

clam eggs. 
Little is known concerning the 

effects of water temperatures on 

development rate of surf clam eggs. 

Fertilized eggs held at an average 

water temperatu re of 21.7OC (71 OF) 

(range 18.3' to 24.g°C or 65O to 

77OF) in the laboratory completed first 

cleavage by 70 min after fertilization 

(Costello et al . 1957). Trochophore 

larvae began appearing 9 hr after 

fertilization (Costello et al . 1957; 

Ropes 1980). Fertilized eggs reached 

the veliger larvae stage in 72 hr at 

14OC (57OF), and in 28 hr at 2Z°C 

(7Z°F) (Loosanoff and Davis 1963). 

Larvae 

Pyramid-shaped, planktonic trochophore larvae began developing from 

swimming gastrulae 9 hr after fertilization at a water temperature of 

21.7OC (71°F) (Costello et al. 1957; 

Ropes 1980). Veliger larvae (first 

appearance of bivalved shell) formed 

by 19 to 20 hr after fertilization, and 

a ciliated velum also appeared at this 

time (Ropes 1980). The velum is used 

for propulsion of the larvae until the 

juvenile or "settlement" phase is 

reached. One day after fertilization, 

veliger larvae averaged 89 microns (p) 

long and 71 p high (Ropes 1980). 

Other reported values for the size of 

veliger larvae at 1 day were (length 

by height) 95 p by 80 p (Sullivan 

1948) and 80 p by 65 p (Loosanoff et 

al. 1966). 

Pediveliger larvae, a transitional, 

"swimming-crawling" larval stage with 

development of a foot for burrowing 

(Carriker 1951), were first observed 

18 days after fertilization at 21.7OC 

(71°F); by 21 days, nearly all veliger 

larvae had developed through the 

brief pediveliger stage and metamorphosed into juvenile clams (complete 

absorption of velum, settlement to the 

substrate, and beginning of sedentary 

life stage) (Ropes 1980). At 14OC 

(57OF) and 2Z°C (7Z°F), metamorphosis to juveniles was first observed 

after 35 and 19 days, respectively. 

Larvae reared at the lower temperature were significantly smaller than 

larvae reared at 2Z°C (7Z°F) (Loosanoff and Davis 1963). 

Detailed descriptions of the anatomical develcpment of surf clam larvae from the trochophore larval stage 

through the juvenile stage are provided by Ropes (1980). A key for 

identifying larvae of 23 clam species 

inhabiting the Middle Atlantic Bight 

and suggestions for general taxonomic 

separation are given in Chanley and 

Andrews (1971). Additional information on species separation is available 

in Loosanoff and Davis (1963) and 

Loosanoff et al. (1966). 

Water currents in areas where 

planktonic surf clam larvae live are 

important in determining eventual patterns of distribution and settlement 

for developing juveniles (Ropes et al. 

1969; Ropes 1980). 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 

(Ropes 1980) . 

Juveniles 

Juvenile surf clams, with a welldeveloped foot for burrowing and fully 

absorbed velum, were present 18 days 

after fertilization at 21 .7OC (71 OF). 

By 21 days, all clam larvae had metamorphosed into juveniles; average size 

was 303 p long by 267 p high (Ropes 

1980). Other reported values were 

(length by height) 270 F( by 245 p 

(Sullivan 1948) and 263 p by 245 p 

(Loosanoff et al. 1966). 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 by a locomotion called 
"leaping" (a push with the foot 

against the substrate) was investigated by Ropes and Merrill (1973). 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 coral- 

- 

lina, were (1) proximity to a predator, (2) inability to burrow in the 

substrate of settlement, and (3) exposure to air (Ansell 1969). Ropes and 

Merrill (1973) 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. 

Adults 

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 (Ropes 

1980). Papillae fringing the siphonal 

openings (IUorse 1919) may aid in preventing sand grains from being drawn 

into the siphon during respiration and 

feeding (Ropes and Merrill 1973). 

Abundance of adults in suitable substrates ranges from loose, fairly 

evenly distributed aggregations (Olsen 

1970) to localized or patchy, dense 

beds, occasionally with individuals 

close enough in the substrate for 

shells to touch (Wilbur 1964; Flowers 

1973; Ropes 1980) . 

Surf clams were a dominant species collected in surveys of inshore 

benthic fauna from southwestern Long 

Island, New York (Steimle and Stone 

1973), and Little Egg Harbor, New 

Jersey (Garlo and Hondo 1973). 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 10.1 m 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 

(Ropes 1979). Inshore distribution of 

surf clams, particularly in estuarine 

zones, is probably limited by salinity 

requirements ( Ropes 1980) (see 

ENVI RONMENTAL REQU I REMENTS - - 

Salinity section). 

Adult surf clams rarely voluntarily vacate their burrows, and under 

natural stimuli alone, may live their 

entire lives in a single burrow. 

Studies by Armstrong (1965), Ropes 

and Merrill (1970), and Ropes and 

Merrill (1973) 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 (Yancey 

and Welch 1968), but survivors of the 

displacement not washed onto the 

beach probably burrow at or near the 

site where they settle after a storm 

(Rcpes and Merrill 1973). 

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 (Westman and Bidwell 1946), 

20-year-old specimens averaging 147 

mm (5.79 inches) (Loesch and Ropes 

1977), and 25-yea r-old specimens 

averaging 164 mm (6.46 inches) (Jones 

et al. 1978). 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 

(Ropes and Ward 1977). 
GROWTH CHARACTERISTICS 

Growth Rates 

In laboratory experiments conducted at 21.7OC (71 OF), length-byheight measurements of veliger larvae 

shells at daily ages were 1 day, 89 p 

by 71 p; 2 days, 89 p by 76 p; 7 

days, 94 p by 79 p; 17 days, 213 p 

by 194 p; and 18 days (beginning of 

pediveliger stage), 245 p by 230 p 

( Ropes 1980) . 

A unique situation for studying 

surf clam growth occurred in a discrete, newly settled clam bed discovered in Chincoteague Inlet, Virginia, 

on 1 October 1964 (Ropes et al. 

1969). Age O+ clams from this bed 

averaged 21.1 mm (0.8 inch) in shell 

length on 28 October 1964. Subsequent samples indicated average shell 

lengths of 42.4 mm (1.7 inches) on 7 

July 1965 (age 1, 68.6 mm (2.7 

inches) on 18 July 1966 (age 2+), and 

90.5 mm (3.6 inches) on 7 August 

1967 (age 3+). During the winter of 

1967-68, heavy losses to predation and 

storm-related mortality reduced this 

population below levels necessary for 

sampling. Projection of the data collected, however, indicated an average 

shell length of 110 mm (4.3 inches) at 

age 4+. 

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 (e.g., Belding 1910; 

Kerswill 1944; Westman and Bidwell 

1946). Growth data from these and 

other studies using the external aging 

method were summarized by Ropes 

(1980). Age and growth techniques 

were refined by National Marine Fisheriei 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 (Ropes 

1980). 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 by 

Chang et al. (1976) and Jones et al. 

(1978) reported age-size relationships 

using cut and polished shells (Table 

1). These data indicate 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 Ropes 

(1980) 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). 

Both Chang et al. (1976) and Jones et 

al. (1978) found that surf clams sampled f rom 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 relatively 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) 

(Ropes and O'Brien 1979). 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 (Ropes and 

O'Brien 1979). 

Length-Weiqht Relationships 

Shell length (L in mm) to 

drained-meat weight (W in g) relationships for surf clam populations of the 

Middle Atlantic Bight were determined 

by Murawski and Serchuk (1981), and 

are presented below for the following 

areas: (1) southern New England, 

(2) New Jersey, (3) Delmarva Peninsula, (4) North Carolina, and (5) all 

areas combined. 
Table 1. Surf clam she1 1 length (mm) at age (yr) for three mid-Atlantic locations, 

determined by the cut-and-polished-she11 technique. 

Shell length (mm) 

Age Point Pleasant, Barnegat Bay Ocean Cit , (yr) New Jerseya New ~erse~~ Mary1 and i: 

aJones et al. 1978. 

b~hang et a1 . 1976. 

Similar relationships for shell length 

to shell height, shell width, shell 

weight, total clam weight, and chondrophore length were given in Chang 

et al. (1976). 

Age- Length/AgVon-Bertalanffy growth equations 

for (1) age (t in yr) to shell le~gth 

(L in mm), (2) age to total live 

weight (W in g), and (3) age to 

drained -meat weight (W in g) were 

determined for Middle Atlantic Bight 

surf clams (Chang et al. 1976) as follows : 

where values in parentheses with 

"exp" represent the exponent of e, 

the base of natural logarithms. 

THE FISHERY 

Commercial Fisheries 

Compared to information available 

on life history and environmental 

requirements of surf clams, information on fishery operations, stock 

assessment, and trend prediction is 

extensive and detailed. Summaries of 

fishery operations for 1972 (Ropes et 

al. 1975a), 1973 (Ropes et al. 1975b), 

and the period 1965 to 1974 (Ropes 

1982) are available. Summaries of the 

geographical distribution of landings, 

relative abundance of exploitable and 
recruiting stocks, fishery operations 

through 1982, and predicted trends in 

the fishery are available in Ropes 

(1979) and Murawski and Serchuk 

(1979, 1981, 1982). The reader is 

referred to these seven studies for 

detailed information on surf clam fisheries and population dynamics. For 

the scope and purpose of this profile, 

only major aspects and trends of the 

fishery are included. 

Earliest methods of harvesting 

surf clams were by hand-operated 

rakes or simply by gathering clams 

from beaches after storms (Parker 

1971). During the 1920's, scrapertype dredges towed behind powerboats were used, but were relatively 

inefficient and broke many clams. In 

the mid-1940ts, the water-jet dredge 

was developed. This innovation 

increased fishing efficiency, decreased 

clam breakage, and was instrumental 

in developing the modern-day surf 

clam fishery (Ropes 1980). 

The present surf clam fishery 

uses a "knife-scraper" dredge with a 

water-jet system mounted ahead of the 

scraper. These dredges are larger 

and heavier than those used in the 

1940's. The knife may be as wide as 

3 m (10 ft), and the water-jet hose as 

large as 20 cm (7.8 inches) in diameter. Special vessel construction is 

now necessary to tow these dredges 

effectively. The addition of stern 

ramps and conveyor systems to clam 

fishing boats constructed or converted 

after 1970 has further increased fishing efficiency (Ropes 1980). 

The commercial fishery for surf 

clams has developed from one during 

World War I I, when surf clams supplied 3.2O" of the U. S. landings of 

clam meats, to an extensive fishery by 

the late 1950's. Between 1970 and 

1974, surf clams provided 71.88 of all 

clam meats used in the United States. 

Per capita consumption of surf clams 

in the United States has doubled from 

0.122 kg (0.268 Ib) in 1947 to 0.267 

kg (0.589 Ib) in 1974. 

Ropes (1982) summarized monthly 

landings and trends of the surf clam 1 

fishery for five States in the Middle 

Atlantic Bight, from 1965 to 1974. 

Over this 9-vear period, landings at 

New York, Maryland, and Delaware 

ports remained relatively stable and 

low compared to those at New Jersey 

and Virginia ports. Landings at New 

Jersey ports declined gradually from 

1965 to 1970, then more rapidly from 

1970 to 1974. Despite the decline, 

New Jersey ports remained the most 

important for total clam landings 

through 1972. Landings at Virginia 

ports began to increase sharply in 

1970 as fishermen shifted their efforts 

southward. By 1974, Virginia landings had surpassed New Jersey landings, and these two States accounted 

for more than 80% of all surf clam 

landings (Ropes 1982). 

Clam stocks and harvests f rom 

New Jersey waters continued to 

decline after 1974, but some signs of 

at least temporary rebuilding of fishable stocks were evident in 1981 trawl 

surveys (Murawski and Serchuk 

1981). In contrast to the New Jersey 

fishery, fisheries off Virginia (including the Delmarva Peninsula) have 

increased in importance to the overall 

fishery. Commercial fisheries apparently continue to shift the concentration of effort southward, since northern stocks remain at relatively low 

levels (Mu raw ski and Serchuk 1981 ) . 

Table 2 summarizes total U. S. 

landings of surf clams between 1965 

and 1981. Percentage of the total 

catch outside State territorial waters 

(greater than 4.8 km or 3 mi offshore) is also given in Table 2 (data 

from Nlurawski and Serchuk 1982, and 

National Marine Fisheries Service 

1978-1982). Total U. S. landings in 

1974 and 1975 were 96.1 million Ib 

(43.6 thousand metric tons (mt)) and 

87.0 million Ib (39.5 thousand mt) of 

shucked meats, respectively. I n 
Table 2. Total U.S. connnercial landings of surf clams (in thousands of 1b of meats), 

U.S. commercial landings from the Fishery Conservation Zone (4.8 to 321.9 km or 3 to 

200 mi offshore), and the percentage of the total landings taken in the Fishery Conservation Zone. 

Total Landings outside Percent of landingsa 

Year 1 andi ngs 3 mi offshore outside 3 mi 

(thousands of lb) (thousands of lb) 

1965 44,088 33,000 74.9 

1966 45,113 32,400 71.8 

1967 45,054 24,700 54.8 

1968 40,552 20,000 49.3 

1969 49,575 15,900 32.1 

1970 67,318 14,100 20.9 

1971 52,535 50,053 95.3 

1972 63,371 55,272 87.1 

1973 82,370 72,579 88.1 

1974 96,110 74,430 77.4 

1975 86,956 44,270 50.9 

1976 49,133 42,558 86.6 

1977 51,036 42,968 84.2 

1978 39,237 31,393 80.0 

1979 34,912 29,070 83.3 

1980 37,737 34,718 92.0 

198 1 46,100 37 ,340b 81.0 

1982 - - - - - - 27,635 ---- 

a~roration for 1972-81 based on data presented in Fisheries of the United States 

(National Marine Fisheries Service 1978-1982). Earlier data from Murawski and 

Serchuk (1982). 

b~nly prel iminary data available for 1982. 

1976, total landings dropped to 49.1 

million Ib (22.3 thousand mt). The 

major reason for the large decline 

between 1975 and 1976 was the collapse of the New Jersey fishery, due 

to large areas of ocean-bottom water 

with low levels (c2.O ppm) of dissolved oxygen during the spring and 

summer of 1976 (see ENVIRONMENTAL 

REQUl REMENTS -- Dissolved Oxygen 

section). Total landings dropped even 

further by 1979, to 34.9 million Ib 

(15.9 thousand mt), but increased 

again in 1980 and 1981 to 37.7 million 

Ib (17.1 thousand mt) and 46.1 million 

Ib (20.9 thousand mt), respectively. 

For landings in 1981, 58% came 

from Delmarva Peninsula fishing areas, 

while 41% came from northern New 

Jersey areas. Only 1% of the catch 

was taken from southern New Jersey, 

which in the 1960's and early 1970's 

had been one of the more important 

clam fishing grounds (Mu raw ski and 

Serchuk 1981). Part of the apparent 

rebound of the sunf clam fishery in 

i980 and 1981 was' due to improved 
resource conditions in the northern 

New Jersey areas. 

Except for 1975, greater than 75% 

of all surf clam landings between 1971 

and 1981 came from areas greater than 

4.8 km (3 mi) offshore (Table 2). In 

1980 and 1981, 92% and 8190, respectively, of the total landings came from 

the U. S. Fishery Conservation Zone 

(4.8 to 321.9 km or 3 to 200 mi offshore). These offshore areas are 

apparently increasing in importance, 

as easier-to-fish but overexploited 

inshore populations remain depleted 

(Mu raw ski and Serchuk 1981). 

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. l ntensive 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) (Murawski and Serchuk 1981). 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 13-cm (3.9- to 5.1-inch) 

clams to the fishery prior to size regulation (Mu rawski and Serchuk 1981). 

The most recent assessments of 

the abundances of fishable and 

recruiting surf clam stocks indicate 

that the relatively strong 1976 year 

class has helped restore northern New 

Jersey fishing grounds. The bulk of 

the 1976 cohort still remains below 

exploitable size (14 cm or 5.5 inches), 

but is predicted to enter the fishery 

in substantial numbers by mid-1983. 

Harvestable biomass in southern New I 

Jersey waters has also increased from 

low levels in the late 1970'~~ but is 

still well below that which was available to fishermen in the late 1960's 

(Murawski and Serchuk 1981). The 

Delmarva Peninsula has maintained 

fairly stable levels of harvestable biomass since it became an important 

fishing ground in the mid-1970's. 

However, most of the 1981 landings 

prior to July 1981 (adoption of the 

size limit) came from the relatively 

strong 1977 year class in the Delmarva 

area, and adoption of the minimum 

size limit curtailed full exploitation of 

this year class until at least 1984 

(Murawski and Serchuk 1981). 

Population Dynamics 

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 (Ropes 1968b). Data 1 

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 

(Ropes 1980). 

Age composition. According to all 

of the clam age data from Ropes 

(1980), the age classes (determined 

by both external and shell-sectioning 

aging techniques) present in samples 

from various mid-Atlantic areas were 

as follows: offshore Virginia, 1 to 19 

(Loesch and Ropes 1977); inshore 

Chincoteague Inlet, Virginia, 1 to 3 

(Ropes et al. 1969); offshore Ocean 

City, Maryland, 1 to 13 (Chang et al. 

1976); inshore Barnegat Bay, New 

Jersey, 1 to 6 (Chang et al. 1976); 

inshore Point Pleasant, New Jersey, 1 

to 11 (Jones et al. 1978); offshore 

Point Pleasant, New Jersey, 1 to 25 
(Jones et al. 1978); offshore central 

New Jersey, 1 to 12 (Ropes 1980); 

and offshore Long Island, New York, 

1 to 17 (Westman and Bidwell 1946). 

These age class data support the 

hypothesis that individuals from offshore, deepwater clam beds live 

longer than those from inshore, shallow water beds. Differences in age 

class structure among populations, 

however, may be because of varying 

degrees of exploitation in inshore and 

offshore beds. 

Recruitment and production. Relative abundance (mean number per 

tow) of recruiting surf clams (less 

than 14.0 cm or 5.5 inches) in 

National Marine Fisheries Service bottom trawl surveys from 1965 to 1978 is 

summarized in Table 3 (data from 

Murawski and Serchuk 1982). Exceptionally high abundances in surveys 

beginning in December 1978 off northern New Jersey and Delmarva Peninsula indicated relatively strong year 

classes in 1976 and 1977 in those 

areas. Young clams from the 1976 and 

1977 year classes were predicted to 

enter the fishery by 1982 (prior to 

establishment of a minimum size limit) 

(Murawski and Serchuk 1979). However, with the adoption of the 14-cm 

(5.5-inch) minimum size limit in July 

1981, these year classes will probably 

not be recruited to the fishery until 

1983 or 1984 (Murawski and Serchuk 

1981). 

In three unexploited surf clam 

beds in the Gulf of St. Lawrence, off 

Buctouche, New Brunswick, density of 

surf clams averaged 1 . 06/m2 

(0.10/ft2) and ranged from 0.68 to 

1.25/mZ (0.06 to 0.12/ft2). Total 

estimated standing crop in these three 

beds, which collectively covered 2.6 

km2 (1.0 miz), was 2.8 million clams 

(Caddy and Billard 1976). 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 f rom 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 

(approxi mately 4.0 cm or.1.6 inches) and 

F=0.5, and (3) age at first capture 3 

years and Fz0.25 (Caddy and Billard 

1976). 

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 recruit. 

Initial catch under model (2) was half 

that of the other models, but longterm 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 (Caddy and BiIIard 

1976). Caddy and Billard (1976) 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). 

ECOLOGICAL ROLE 

Food Habits 

In Iaboratory-reared surf clam 

larvae, yolk material was fully 

absorbed and algal cells began 

appearing in some stomachs at 1 day 
Table 3. Relative abundance (mean number per standardized 5-min tow) of recruiting (less than 14.0 cm or 5.5 inches) surf clams from National Marine Fisheries 

Service surveys, 1965-82, in the Fishery Conservation Zone offshore of northern 

New Jersey, southern New Jersey, Delmarva Peninsula, and Vi rgi nia-North Carol ina 

(data from lvlurawski and Serchuk 1982). 

Northern Southern Del marva VirginiaCruise period New Jersey New Jersey Peninsula N. Carolina 

May 1965 

Oct 1965 

Aug 1966 

Jun 1969 

Aug 1970 

Jun 1974 

Apr 1976 

Jan 1977 

Jan 1978 

Dec 1978 

Jan 1980 

Aug 1980 

Aug 1981 

Aug 1982 

a~nly asmall portion of the total Virginia-North Carolina offshore area was 

surveyed. 

of age (veliger larvae) (Ropes 1980). 

Larval surf clams fed on algal cells 

throughout the remainder of the stage 

(Ropes 1980). Loosanoff and Davis 

(1950, 1963) 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 (1968) 

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. 

Stomachs of adult surf clams from 

New Jersey coastal waters contained a 

variety of diatom genera and species, 

but only Amphipora constricta and 

Tintinnus spp. were identified f rom 

the contents (Leidy 1878). Difficulties in identification were caused by 

change in diatom structure after entry 

into the surf clam's digestive tract. 

Stephens and Schinske (1961) 

observed that the amino acids glycine, 

glutamic acid, tyrosine, methionine, 

phenylalinine, and arginine were successfully removed from food items 

ingested by surf clams, and appeared 

to be of nutritional value. Food consumed and assimilated by surf clams 

probably depends on geographic location and depth of the bed, seasonal 

variation in availability of food items 

and feeding activity, and annual or 

long-term fluctuations in diversity and 

abundance of food organisms. 
Feeding Behavior 

Like many bivalves, surf clams 

are plan ktivorous, siphon feeders. 

Feeding activity of surf clams is intimately associated with the overall process of siphoning water for respiration 

and excretion (Ropes 1980). Feeding 

surf clams burrow deep enough in the 

substrate so that the end of the 

incurrent siphon barely protrudes 

above the bottom (Ropes and Merrill 

1976). 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 (Morse 

1919; Jacobsen 1972). 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 (Jacobsen 

1972). Food particles trapped on the 

mucus-coated inner siphonal surfaces 

move unidirectionally with the mucus 

toward the gut of the clam (Kellog 

1915). Morphology and responses of 

the incurrent siphonal valve and 

adductor muscles of surf clams, used 

to clean debris from the siphonal cavity, were described by Prior (1974). 

The crystalline style in the digestive 

tract stirs the stomach contents and 

aids in producing and excreting 

enzymes for digestion (Ropes 1980). 

Studies have been conducted on the 

enzymes and enzymatic processes in 

the surf clam gut (Lavine 1946; Patton 

and Quinn 1973; Shallenberger et al. 

1974, 1975; Lindley and Shallenberger 

1976, 1977) and on the neurophysiological mechanisms of gut movements 

(Nystrom 1976; Smucker and Nystrom 

1970, 1972). 

-- 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 (e.g., Hunt 1925; 

Birkett and Wood 1959; Thorson 1966; 

Muus 1966, 1973; Christensen 1970; 

Masse 1975), 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 (Hanks 

1952). In laboratory experiments P. 

duplicatus ceased feeding at 5c~ 

(41°F) or lower and 6 ppt salinity, 

while L. heros reduced feeding at 2OC 

(35.6OT) or lower and ceased feedina 

below 1.0 ppt salinity. Lunatia heros 

may be a size-selective predator on 

surf clams, since Franz (1977) found 

that most surf clams selected by snails 

off Long Island were less than 80 mm 

(3.1 inches) 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 

(Pratt 1974). 

Predatory fish reported to consume surf clams are haddock (Melanogrammus aeglefinus) (Clapp 1912; 

Clarke 1954) and cod (Gadus -- morhua) 

(Bigelow and Schroeder 1953; Clarke 

1954). 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. 

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 ( Ropes 1980). 

Some evidence exists for intraspecific competition in dense, inshore 

surf clam beds, including roughened 

shell surfaces and edges, older shell 

deposits raised one on top of another 

Ii ke shingles, and blunted posterior 

ends of shells (Ropes 1980). These 

features are generally unique to dense 

populations and may indicate disruption in growth patterns through some 

competition among clams for space or 

food (Ropes 1980). In Iaboratory 

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 (Wilbur 

1964). 

ENVI RONMENTAL REQUl REMENTS 

Surf clam larvae tolerated a water 

temperature range from 14OC to 30°C 

(57OF to 86OF) (Loosanoff and Davis 

1963). Optimum temperature for larval development was 22OC (72OF) 

(Loosanoff and Davis 1963). Juvenile 

surf clams survived higher temperatures than adults, but became inactive 

at 4OC (3g°F) or lower (Saila and 

Pratt 1973). Survival of spawning 

adults and their fertilized eggs was 

significantly affected at water 

temperatures of 30°C (86OF) or higher 

(Loosanoff and Davis 1963). Adult 

surf clams were unable to establish 

pedal anchorage at water temperatures 

greater than 30°C (86OF) (Savage ( 

1976). Lethally low water temperatures for adult surf clams are probably never reached in their oceanic 

habitat, but low air temperatures (less 

than O°C or 32OF) may freeze exposed 

gill tissue in live clams temporarily 

washed up onto the beach during 

storms ( Ropes 1980). 

In Iaboratory experiments, the 

burrowing rate of surf clams increased 

as water temperature increased to 

20°C (68OF), but decreased above this 

temperature (Savage 1976). Some 

clams failed to begin digging activities 

at water temperatures below 2OC 

(36OF), and others began digging but 

could not accomplish complete burial at 

that temperatu re. Temperature 

shocks induced by a 14OC (25OF) 

increase in water temperature, with a 

starting temperature of 4OC (3g°F), 

did not significantly affect burrowing. 

A temperature increase of 22OC (40°F) 

produced gaping, lethargy, and eventually death (Ropes 1980). 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). 

Salinity 

Minimum salinities for larval and 

adult surf clam survival were 16 ppt 

and 12.5 ppt, respectively (Castagna 

and Chanley 1973). Adult surf clams 

tolerated salinities from 14 ppt to 52 

ppt (concentrated seawater) (Theede 

1965). Encroachment of surf clams 

into estuarine areas is probably limited by salinity (Ropes 1980). 

Dissolved Oxygen 

Several instances of severe 

depletion of dissolved oxygen in the 

bottom waters of the ocean (equivalent 
to the hypolimnion in freshwater) , along the New Jersey and Long Island 

coasts, have produced surf clam mortalities. A major event of this type 

occurred in the spring and summer of 

1976. Anoxic water developed over 

clam beds between Cape May, New 

Jersey, and Long Island's south 

shore, out to a depth of 75 m (246 

ft), because of the combined effects 

of meteorological and hydrographic 

conditions, organic loading from 

human waste dump sites, and an 

unusually large bloom and die-off of 

the dinoflagellate Ceratium tripos 

(Steimle and Sindermann 1978). The 

kill area was estimated at 6,750 km2 

(2,605 mi2), and the loss of meat 

weights was estimated at 147 thousand 

mt (162 thousand tons), representing 

62% of the New Jersey surf clam 

resource (Steimle and Sindermann 

1978; Ropes 1980). Dissolved oxygen 

isopleths measured during the kill 

period indicated an area of approximately 278 km2 (107 mi2) (approximately 12.8 km or 8 mi southeast of 

Barnegat Inlet, New Jersey) where 

hypolimnetic waters contained no 

measurable dissolved oxygen. A total 

area of approximately 9,722 km2 

(3,752 mi2) contained 1 .O ppm dissolved oxygen or less in the hypolimnion. Nearly the entire area along 

the New Jersey coast, from the shoreward limit of the hypolimnion to a 

depth of 75 m (246 ft), contained 2.0 

ppm or less dissolved oxygen (Steimle 

and Sindermann 1978). Other important commercial shellfish, such as 

ocean quahogs (Artica islandica) and 

sea scallops (Placopecten magellanicus) 

were also affected, as well as some 

finfish populations. 

All available evidence indicated 

that the specific events that caused 

development of anoxic bottom waters 

in 1976 were (1) an unusually warm 

winter, with highest river runoff in 

February rather than April, thus 

allowing early development of dense 

dinoflagellate populations; (2) earlier 

than normal thermal stratification, 

sealing off organically rich, oxygendemanding water (from dead and 

dying dinoflagellates) early in the 

spring; (3) additional organic loading 

from human waste dump sites off New 

Jersey and Long Island; (4) limited 

water mass movement for an extended 

period (4-6 weeks), due to a persistent southerly flow of air; and 

(5) abnormally low cyclonic storm activity over the same 4- to 6-week period. 

Any one of these events probably 

would not have caused oxygen depletion to the extent observed, but 

together they devastated New Jersey 

and Long Island surf clam populations 

(Steimle and Sindermann 1978). 

Little specific information is 

available concerning the long-term or 

short-term dissolved oxygen requirements of surf clams. However, since 

part of the estimated kill zone in 1976 

was between the 1 .O-ppm and 2.0-ppm 

dissolved oxygen isopleths, a lower 

lethal limit of 2.0 ppm can be assumed 

until more detailed information on 

oxygen requirements is collected. 

Prior to 1976, other less extensive 

oxygen depletion events and associated surf clam mortalities had been 

observed (Ogren 1969; Ogren and 

Chess 1969; Young 1973). In addition 

to causing mortality, low dissolved 

oxygen concentrations (values not 

given) were reported to depress burrowing activities of surf clams (Savage 

1976) and may be a stimulus for surf 

clams to vacate their burrows (Ropes 

1980). 

Other Environmental Factors 

Though specific studies are lacking, water currents are thought to be 

important in influencing distribution of 

planktonic, larval stages of the surf 

clam, and in the development of new 

surf clam beds (Ropes 1980). Major 

water current patterns over weeks or 

months may also influence availability 

of dissolved oxygen in the oceanic 

hypolimnion, and in combination with 

other abiotic and biotic events, may 
influence surf clam mortality rates 

(see ENVIRONMENTAL REQUIREMENTS 

-- Dissolved Oxygen section). 

Hydraulic water-jet dredges used 

by commercial fishermen to harvest 

clams apparently do not stimulate 

uncaptured individuals to actively 

leave the area, since these fishermen 

may repeatedly dredge the same areas 

for weeks or months (hotspots), and 

continually take clams in commercially 

usable numbers (Ropes and Merrill 

1973). These same water-jet dredges, 

however, may affect survival of 

uncaptured clams by increasing exposure to snail predators. Also, uncaptured surf clams are prone to injury 

from the water-jets because their 

shells gape slightly at the siphon end. 

The water-jets force the shells open, 

expose the soft bodies to predation, 

and disrupt normal respiration, feeding, and excretion (Ropes 1980). 

Surf clams in general are less hardy 

than hard clams (Mercenaria mercenaria), which can close their shells 

tightly (Ropes 1980). MacKenzie 

(f982) concluded that hydraulic 

dredges used in commercial fisheries 

for ocean quahogs (a closely related 

mactrid) off New Jersey did not signif icantly affect abundance of invertebrates in areas of dredging. 

Pollutants 

Two major classes of pollutants 

have been documented to affect surf 

clam populations or exploitation of 

those populations: (1) human refuse, 

sewage, and sludge (oceanic dump 

sites), and (2) metals. 

Zoellner (1977) reviewed water 

quality problems related to molluskan 

shellfish and the effectiveness of current discharge control laws. Although 

natural phenomena, dredging, and 

chemical contamination were all noted 

as having significant impacts on 

shellfish populations, he considered 

domestic waste discharge to have the 

greatest negative impact on sanitary 

conditions in and around shellfish 

beds. Positive fecal coliform counts 

were reported in 70% of surf clam 

samples taken offshore of Delaware 

Bay in 1966 and 1967 (Buelow 1968). ( Areas in the New York Bight contaminated with human fecal coliforms were 

contiguous with sewage and sludge 

disposal sites, and extended northeastward 11 km (6.8 mi) and southward 37 km (23.0 mi) from Hudson 

River Estuary dumping sites (Babinchak et al. 1977). Pearc'e (1972) concluded that "normal benthic communities" in the New York Bight had been 

significantly altered by solid waste 

disposal in the bight. In most areas 

of solid waste dumping, surf clams 

were a dominant bivalve in an otherwise low-diversity, high-dominance 

assemblage (Pearce 1972). This general degradation of community diversity was also noted by O'Connor 

(1976). Commercial size surf clams 

were rare in a 1,550-km2 (598-mi2) 

area surrounding dump sites off New 

Jersey, even though surf clams were 

common outsidr the immediate areas of 

dumping. 

The continual leaching of contaminants from oceanic dump sites into 

the water and sediments and the 

uptake by sedentary oceanic fauna 

such as the surf clam have forced 

closure of various important clamharvesting areas of the Middle Atlantic 

Bight over the past two decades. 

Most areas closed during this period 

were between Delaware Bay and the 

southeast end of Long Island (Verber 

1976; Babinchak et al. 1977; Ritchie 

1977). An approximate total area of 

1,580 km2 (610 mi2) of the Middle 

Atlantic Bight was and remains closed 

because of contaminants in clam bodies 

from dump sites (Ropes 1980). A 

further effect of dump sites is the 

contribution to biological oxygen 

demand in the oceanic bottom waters 

(see ENVIRONMENTAL REQUIREMENTS -- Dissolved Oxygen section), 

thereby increasing surf clam mortalities due to natural periodic depletions 
of oxygen in bottom waters of the 

ocean (Steimle and Sindermann 1978). 

Studies have delineated lethal 

concentrations of certain heavy metals 

and determined sublethal concentrations contained in natural populations 

of surf clams. In laboratory studies, 

96-hr LC50 values for silver were 

(1 )between 50 ppb and 100 ppb for juveniles, and (2) greater than 100 ppb 

for adults (Thurberg et al. 1975). 

Sublethal effects (observed for larvae 

at 50 ppb and juveniles at 10 ppb) 

appeared as increases in metabolic 

oxygen requirement and rhythmic 

valve movement, both indicators of 

higher respiration and filtration rates. 

Silver accumulated rapidly in gills and 

other body tissues of test specimens, 

and silver concentrations in gill tissues were four times as high as concentrations in other body tissues 

(Thurberg et al. 1975). 

Elevated concentrations of iron 

and copper (Lear et al. 1973) and 

chromium and nickel (Buelow 1968) 

were found in surf clams collected 

near sewage' and acid waste dump 

sites offshore of Delaware Bay. 

Recently, the Environmental Protection 

Agency estimated that an area of 

3,600 km2 (1,389 mi2) off Maryland 

and Delaware had several potentially 

toxic metals in sediments and organisms. Though surf clams were not 

analyzed, two closely related species 

from the area, ocean quahogs and sea 

scallops, contained elevated concentrations of vanadium in their body 

tissues (Lear and Pesch 1975). 

Relatively high concentrations of 

cadmium, copper, nickel, vanadium, 

chromium, and zinc were found in 

surf clams from Delaware Bay (Reynolds 1979), though sample sizes were 

too small to test statistically. Mean 

arsenic levels in Middle Atlantic Bight 

surf clams ranged from 1.46 ppm to 

2.66 ppm, a range exceeding allowable 

levels (1.14 ppm) recommended by the 

Australian National Health and Medical 

Research Council (Wenzloff et al. 

1979) (no levels recommended by 

Environmental Protection Agency) . 
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50272-101 

I REPORT DOCUMENTATION I?.-REP~RT NO. 2. 3. Recipient's Accession NO. 1 

-- - 7. Author(s) 8. Performing Organization Rept. No. 

Clemon W. Fav, Richard J. Neves, and Garland 0. Pardue 

and Environmentai 

Requirements of Coastal Fishes and Invertebrates (Mid-Atlantic) -- 

Surf Clam 

- 9. Performing Organization Name and Address 

=-Fisheries and Wi id1 i fe Sciences 

5. Report Date 

October 1983 6. 

virginia Polytechnic Institute and State University 

Bl ac ks burg, VA 24061 

1 fixt=~rant(G) No. 

I *U.S. Army Corps of Engineers report No. TR EL-82-4. 

I16. Abstract (Ltmlt. 200 words) 

The surf clam (Spisula s o l i d i s s i m a ) is a dominant clam species in the mid-Atlantic region, 

and contributed 71.8% of all clam meats consumed in the United States between 1970 and 

1974; total landings in 1981 were 20.9 thousand metric tons (46.1 million Ib). Surf clams 

live in the coastal zone from the Gulf of Maine to Cape Hatteras, North Carolina; they are 

most common in the breaker zone, but occur to depths of 70 m (230 ft). They reach sexual 

maturity in 2 years and spawn in the mid-Atlantic region from mid-July through mid-October, 

often with two spawning peaks per year. Larval stages are planktonic; upon settlement, thej 

metamorphose into juvenile clams. Adults live buried in sandy or gravel substrates, with 

siphons extended above the bottom for feeding and respiration. Surf clams may live up to 

25 years and reach a size of 225 mrn (8.9 inches). Larvae tolerate water temperatures of 14' 

to 30" C (57" to 86" F), and salinities as low as 16 ppt. Adults tolerate 0" to 28" C (32" 

to 82" F) and 12.5 ppt sal inity or higher. Depletion of dissolved oxygen in ocean bottom 

waters was the major cause for large-scale surf clam mortalities off New York and New Jersej 

over the last two decades. Sewage, sludge, and heavy metals often cause accumulation of 

toxic materials in surf clam meats and force closure of beds to fishing to prevent human 

consumption of these toxic materials. 

National Coastal Ecosystems Team U.S. Army Corps of Engineers 

Fish and Wildlife Service Waterways Experiment Station 

U.S. Department of the Interior P.O. Box 631 

Washington, DC 20240 Vicksburg, MS 39180 

-- 

Coastal Zone Feed i ng 

Clams Growth 

Distribution 

13. Type of Report & Period Covered 

- 

14. 

b. Identifierr/Open.Ended Terms 

Surf clam Depth distribution 

Spisula s o l i d i s s i m a Temperature requirements 

Substrate requirements 

18. Availability Statement 19. Security Class (This Report) 

Unlimited 1 Unclassified 20. Security Class (This Page) 

Unclassified 

21. No. of Pages 

23 -- 

22. Price 

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