NOAA Technical Memorandum NMFS-NE-134

Essential Fish Habitat Source Document:

Sea Scallop, Placopecten magellanicus,

Life History and Habitat Characteristics

U. S. DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

National Marine Fisheries Service

Northeast Region

Northeast Fisheries Science Center

Woods Hole, Massachusetts

September 1999
Recent Issues

105. Review of American Lobster (Homarus americanus) Habitat Requirements and Responses to Contaminant Exposures.

By Renee Mercaldo-Allen and Catherine A. Kuropat. July 1994. v + 52 p., 29 tables. NTIS Access. No. PB96-115555.

106. Selected Living Resources, Habitat Conditions, and Human Perturbations of the Gulf of Maine: Environmental and

Ecological Considerations for Fishery Management. By Richard W. Langton, John B. Pearce, and Jon A. Gibson, eds.

August 1994. iv + 70 p., 2 figs., 6 tables. NTIS Access. No. PB95-270906.

107. Invertebrate Neoplasia: Initiation and Promotion Mechanisms -- Proceedings of an International Workshop, 23 June

1992, Washington, D.C. By A. Rosenfield, F.G. Kern, and B.J. Keller, comps. & eds. September 1994. v + 31 p., 8 figs.,

3 tables. NTIS Access. No. PB96-164801.

108. Status of Fishery Resources off the Northeastern United States for 1994. By Conservation and Utilization Division,

Northeast Fisheries Science Center. January 1995. iv + 140 p., 71 figs., 75 tables. NTIS Access. No. PB95-263414.

109. Proceedings of the Symposium on the Potential for Development of Aquaculture in Massachusetts: 15-17 February 1995,

Chatham/Edgartown/Dartmouth, Massachusetts. By Carlos A. Castro and Scott J. Soares, comps. & eds. January 1996.

v + 26 p., 1 fig., 2 tables. NTIS Access. No. PB97-103782.

110. Length-Length and Length-Weight Relationships for 13 Shark Species from the Western North Atlantic. By Nancy E.

Kohler, John G. Casey, Patricia A. Turner. May 1996. iv + 22 p., 4 figs., 15 tables. NTIS Access. No. PB97-135032.

111. Review and Evaluation of the 1994 Experimental Fishery in Closed Area II on Georges Bank. By Patricia A. Gerrior,

Fredric M. Serchuk, Kathleen C. Mays, John F. Kenney, and Peter D. Colosi. October 1996. v + 52 p., 24 figs., 20 tables. NTIS

Access. No. PB98-119159.

112. Data Description and Statistical Summary of the 1983-92 Cost-Earnings Data Base for Northeast U.S. Commercial

Fishing Vessels: A Guide to Understanding and Use of the Data Base. By Amy B. Gautam and Andrew W. Kitts. December

1996. v + 21 p., 11 figs., 14 tables. NTIS Access. No. PB97-169320.

113. Individual Vessel Behavior in the Northeast Otter Trawl Fleet during 1982-92. By Barbara Pollard Rountree. August 1997.

v + 50 p., 1 fig., 40 tables. NTIS Access. No. PB99-169997.

114. U.S. Atlantic and Gulf of Mexico Marine Mammal Stock Assessments -- 1996. By Gordon T. Waring, Debra L. Palka, Keith

D. Mullin, James H.W. Hain, Larry J. Hansen, and Kathryn D. Bisack. October 1997. viii + 250 p., 42 figs., 47 tables. NTIS

Access. No. PB98-112345.

115. Status of Fishery Resources off the Northeastern United States for 1998. By Stephen H. Clark, ed. September 1998. vi

+ 149 p., 70 figs., 80 tables. NTIS Access. No. PB99-129694.

116. U.S. Atlantic Marine Mammal Stock Assessments -- 1998. By Gordon T. Waring, Debra L. Palka, Phillip J. Clapham, Steven

Swartz, Marjorie C. Rossman, Timothy V.N. Cole, Kathryn D. Bisack, and Larry J. Hansen. February 1999. vii + 182 p., 16

figs., 56 tables. NTIS Access. No. PB99-134140.

117. Review of Distribution of the Long-finned Pilot Whale (Globicephala melas) in the North Atlantic and Mediterranean.

By Alan A. Abend and Tim D. Smith. April 1999. vi + 22 p., 14 figs., 3 tables. NTIS Access. No. PB99-165029.

118. Tautog (Tautoga onitis) Life History and Habitat Requirements. By Frank W. Steimle and Patricia A. Shaheen. May 1999.

vi + 23 p., 1 fig., 1 table. NTIS Access. No. PB99-165011.

119. Data Needs for Economic Analysis of Fishery Management Regulations. By Andrew W. Kitts and Scott R. Steinback.

August 1999. iv + 48 p., 10 figs., 22 tables. NTIS Access. No. PB99-171456.

120. Marine Mammal Research Program of the Northeast Fisheries Science Center during 1990-95. By Janeen M. Quintal and

Tim D. Smith. September 1999. v + 28 p., 4 tables, 4 app. NTIS Access. No. PB2000-100809.
U. S. DEPARTMENT OF COMMERCE

William Daley, Secretary

National Oceanic and Atmospheric Administration

D. James Baker, Administrator

National Marine Fisheries Service

Penelope D. Dalton, Assistant Administrator for Fisheries

Northeast Region

Northeast Fisheries Science Center

Woods Hole, Massachusetts

September 1999

Essential Fish Habitat Source Document:

Sea Scallop, Placopecten magellanicus,

Life History and Habitat Characteristics

 David B. Packer1, Luca M. Cargnelli1, Sara J. Griesbach1,

and Sandra E. Shumway2

1

National Marine Fisheries Serv., James J. Howard Marine Sciences Lab., 74 Magruder Rd., Highlands, NJ 07732

2

Southampton Coll., Long Island Univ., Southampton, NY 11968

This series represents a secondary level of scientifiic publishing. All issues employ

thorough internal scientific review; some issues employ external scientific review.

Reviews are -- by design -- transparent collegial reviews, not anonymous peer reviews.

All issues may be cited in formal scientific communications.

NOAA Technical Memorandum NMFS-NE-134
Editorial Notes on Issues 122-152

in the

NOAA Technical Memorandum NMFS-NE Series

Editorial Production

For Issues 122-152, staff of the Northeast Fisheries Science Center's (NEFSC's) Ecosystems Processes Division have

largely assumed the role of staff of the NEFSC's Editorial Office for technical and copy editing, type composition, and

page layout. Other than the four covers (inside and outside, front and back) and first two preliminary pages, all preprinting

editorial production has been performed by, and all credit for such production rightfully belongs to, the authors and

acknowledgees of each issue, as well as those noted below in "Special Acknowledgments."

Special Acknowledgments

David B. Packer, Sara J. Griesbach, and Luca M. Cargnelli coordinated virtually all aspects of the preprinting editorial

production, as well as performed virtually all technical and copy editing, type composition, and page layout, of Issues

122-152. Rande R. Cross, Claire L. Steimle, and Judy D. Berrien conducted the literature searching, citation checking,

and bibliographic styling for Issues 122-152. Joseph J. Vitaliano produced all of the food habits figures in Issues 122-

152.

Internet Availability

Issues 122-152 are being copublished, i.e., both as paper copies and as web postings. All web postings are, or will soon

be, available at: www.nefsc.nmfs.gov/nefsc/habitat/efh. Also, all web postings will be in "PDF" format.

Information Updating

By federal regulation, all information specific to Issues 122-152 must be updated at least every five years. All official

updates will appear in the web postings. Paper copies will be reissued only when and if new information associated with

Issues 122-152 is significant enough to warrant a reprinting of a given issue. All updated and/or reprinted issues will retain

the original issue number, but bear a "Revised (Month Year)" label.

Species Names

The NMFS Northeast Regions policy on the use of species names in all technical communications is generally to follow

the American Fisheries Societys lists of scientific and common names for fishes (i.e., Robins et al. 1991a), mollusks (i.e.,

Turgeon et al. 1998b

), and decapod crustaceans (i.e., Williams et al. 1989c), and to follow the Society for Marine

Mammalogy's guidance on scientific and common names for marine mammals (i.e., Rice 1998d). Exceptions to this policy

occur when there are subsequent compelling revisions in the classifications of species, resulting in changes in the names

of species (e.g., Cooper and Chapleau 1998e

).

a

Robins, C.R. (chair); Bailey, R.M.; Bond, C.E.; Brooker, J.R.; Lachner, E.A.; Lea, R.N.; Scott, W.B. 1991. Common and scientific names of fishes

from the United States and Canada. 5th ed. Amer. Fish. Soc. Spec. Publ. 20; 183 p.

b

Turgeon, D.D. (chair); Quinn, J.F., Jr.; Bogan, A.E.; Coan, E.V.; Hochberg, F.G.; Lyons, W.G.; Mikkelsen, P.M.; Neves, R.J.; Roper, C.F.E.;

Rosenberg, G.; Roth, B.; Scheltema, A.; Thompson, F.G.; Vecchione, M.; Williams, J.D. 1998. Common and scientific names of aquatic

invertebrates from the United States and Canada: mollusks. 2nd ed. Amer. Fish. Soc. Spec. Publ. 26; 526 p.

c

Williams, A.B. (chair); Abele, L.G.; Felder, D.L.; Hobbs, H.H., Jr.; Manning, R.B.; McLaughlin, P.A.; Pérez Farfante, I. 1989. Common and

scientific names of aquatic invertebrates from the United States and Canada: decapod crustaceans. Amer. Fish. Soc. Spec. Publ. 17; 77 p.

d

Rice, D.W. 1998. Marine mammals of the world: systematics and distribution. Soc. Mar. Mammal. Spec. Publ. 4; 231 p.

e

Cooper, J.A.; Chapleau, F. 1998. Monophyly and interrelationships of the family Pleuronectidae (Pleuronectiformes), with a revised classification.

Fish. Bull. (U.S.) 96:686-726.
Page iii

FOREWORD

One of the greatest long-term threats to the viability of

commercial and recreational fisheries is the continuing

loss of marine, estuarine, and other aquatic habitats.

Magnuson-Stevens Fishery Conservation and

Management Act (October 11, 1996)

The long-term viability of living marine resources depends

on protection of their habitat.

NMFS Strategic Plan for Fisheries

Research (February 1998)

The Magnuson-Stevens Fishery Conservation and

Management Act (MSFCMA), which was reauthorized

and amended by the Sustainable Fisheries Act (1996),

requires the eight regional fishery management councils to

describe and identify essential fish habitat (EFH) in their

respective regions, to specify actions to conserve and

enhance that EFH, and to minimize the adverse effects of

fishing on EFH. Congress defined EFH as “those waters

and substrate necessary to fish for spawning, breeding,

feeding or growth to maturity.” The MSFCMA requires

NMFS to assist the regional fishery management councils

in the implementation of EFH in their respective fishery

management plans.

NMFS has taken a broad view of habitat as the area

used by fish throughout their life cycle. Fish use habitat

for spawning, feeding, nursery, migration, and shelter, but

most habitats provide only a subset of these functions.

Fish may change habitats with changes in life history

stage, seasonal and geographic distributions, abundance,

and interactions with other species. The type of habitat,

as well as its attributes and functions, are important for

sustaining the production of managed species.

The Northeast Fisheries Science Center compiled the

available information on the distribution, abundance, and

habitat requirements for each of the species managed by

the New England and Mid-Atlantic Fishery Management

Councils. That information is presented in this series of

30 EFH species reports (plus one consolidated methods

report). The EFH species reports comprise a survey of the

important literature as well as original analyses of fisheryJAMES J. HOWARD MARINE SCIENCES LABORATORY

HIGHLANDS, NEW JERSEY

SEPTEMBER 1999

independent data sets from NMFS and several coastal

states. The species reports are also the source for the

current EFH designations by the New England and MidAtlantic Fishery Management Councils, and have

understandably begun to be referred to as the “EFH source

documents.”

NMFS provided guidance to the regional fishery

management councils for identifying and describing EFH

of their managed species. Consistent with this guidance,

the species reports present information on current and

historic stock sizes, geographic range, and the period and

location of major life history stages. The habitats of

managed species are described by the physical, chemical,

and biological components of the ecosystem where the

species occur. Information on the habitat requirements is

provided for each life history stage, and it includes, where

available, habitat and environmental variables that control

or limit distribution, abundance, growth, reproduction,

mortality, and productivity.

Identifying and describing EFH are the first steps in

the process of protecting, conserving, and enhancing

essential habitats of the managed species. Ultimately,

NMFS, the regional fishery management councils, fishing

participants, Federal and state agencies, and other

organizations will have to cooperate to achieve the habitat

goals established by the MSFCMA.

A historical note: the EFH species reports effectively

recommence a series of reports published by the NMFS

Sandy Hook (New Jersey) Laboratory (now formally

known as the James J. Howard Marine Sciences

Laboratory) from 1977 to 1982. These reports, which

were formally labeled as Sandy Hook Laboratory

Technical Series Reports, but informally known as “Sandy

Hook Bluebooks,” summarized biological and fisheries

data for 18 economically important species. The fact that

the bluebooks continue to be used two decades after their

publication persuaded us to make their successors – the 30

EFH source documents – available to the public through

publication in the NOAA Technical Memorandum NMFSNE series.

JEFFREY N. CROSS, CHIEF

ECOSYSTEMS PROCESSES DIVISION

NORTHEAST FISHERIES SCIENCE CENTER
Page v

Contents

Introduction...............................................................................................................................................................................................1

Life History ...............................................................................................................................................................................................1

Habitat Characteristics ..............................................................................................................................................................................4

Geographical Distribution.........................................................................................................................................................................5

Status of the Stocks ...................................................................................................................................................................................5

Research Needs .........................................................................................................................................................................................6

Acknowledgments.....................................................................................................................................................................................6

References Cited .......................................................................................................................................................................................6

Tables

Table 1. Summary of life history and habitat parameters for the sea scallop, Placopecten magellanicus.............................................12

Table 2. Relative abundance of sea scallops in New England bays and estuaries by salinity zone .......................................................15

Figures

Figure 1. The sea scallop, Placopecten magellanicus (from Mullen and Moring 1986) ........................................................................16

Figure 2. Generalized life cycle of the sea scallop..................................................................................................................................17

Figure 3. Map of Georges Bank indicating the five sub-regions and the clockwise flow of the residual current ...................................18

Figure 4. Distribution of sea scallop spawning beds off the northeast coast of North America..............................................................19

Figure 5. Distribution of sea scallops collected during NEFSC scallop surveys during summer 1982-1997 .........................................20

Figure 6. Commercial landings and survey indices of sea scallops for the Gulf of Maine, Georges Bank, and Mid-Atlantic................21
Page 1

INTRODUCTION

The Atlantic sea scallop, Placopecten magellanicus

(Gmelin), is a bivalve mollusk of the family Pectinidae

(Figure 1). It occurs on the continental shelf of the

northwest Atlantic, from the north shore of the Gulf of St.

Lawrence south to Cape Hatteras, North Carolina. An

economically important species, the sea scallop is

managed under the New England Fishery Management

Council’s Sea Scallop Management Plan (NEFMC 1993).

This Essential Fish Habitat source document provides

information on the life history and habitat characteristics

of sea scallops inhabiting U.S. waters in the Gulf of

Maine, Georges Bank, and the Middle Atlantic Bight.

LIFE HISTORY

A brief synopsis of the life history characteristics of

sea scallops is provided in Amendment #4 to the Sea

Scallop Fishery Management Plan (NEFMC 1993). More

detailed information is presented here and in reviews by

Stewart and Arnold (1994) and Shumway et al. (in prep.).

The life cycle of the sea scallop is summarized in Figure

2.

EGGS

The average diameter of spawned eggs is 66.8±1.6

μm (Langton et al. 1987). After fertilization, the eggs are

slightly heavier than seawater and probably remain on the

sea floor as they develop into the first free-swimming

larval stages. The incubation period of eggs maintained in

the laboratory at 13-17o

C is 32 days (Langton et al. 1987).

LARVAE

The two larval stages of the sea scallop, trochophore

and veliger, are pelagic. The larvae remain planktonic for

over a month after hatching (Posgay 1982). The larvae

drift with water currents, but can also swim freely, and

appear to follow a daily vertical migration of up to several

meters, occupying shallower depths at night (Tremblay

and Sinclair 1988, 1990a; Gallager et al. 1996; Manuel et

al. 1996b). They have been shown to migrate in response

to both tidal and solar stimuli (Manuel et al. 1997).

During the day larvae tend to aggregate at the thermocline

(Gallager et al. 1996) and are seldom found below the

thermocline until 21 days post-fertilization (Manuel et al.

1996b). Tremblay and Sinclair (1990b) found that in

well-mixed areas, larvae were distributed evenly through

the water column, while in stratified areas they aggregated

above the pycnocline.

During the planktonic stage, the shell, eye spots, and

foot develop (Naidu 1991). A description of larval

development in the laboratory has been published by

Culliney (1974) and growth of larval scallops in the

laboratory has been studied by Hurley et al. (1986).

Duration of the larval stages is shorter at higher

temperatures and where food is more plentiful.

Identification of planktonic sea scallop larvae in the

wild has only recently been described (Tremblay et al.

1987) and the horizontal distribution of larval scallops is

still largely unknown. Since scallop larvae are planktonic,

speculation about their movement is based largely on the

flow of currents in and around spawning areas.

The mechanism by which recruitment occurs in major

production areas is conjectural at this point. The beds on

Georges Bank, particularly in the vicinity of the Northern

Edge, Northeast Peak, and Great South Channel, are

thought to be self-sustaining at a fairly consistent and

relatively high rate of recruitment. This is probably

because the larvae are retained in the Georges Bank gyre

(see Figure 3) long enough for metamorphosis to be

complete. During the spawning season in September, the

water currents form tight gyrals which confine the larvae

to the Georges Bank area prior to settlement. Good year

classes on Georges Bank are associated with tight

autumnal gyrals and poorer year classes are associated

with loose gyrals (Posgay 1950).

Tremblay and Sinclair (1986) reported on the

horizontal distribution of larval scallops within the Bay of

Fundy. They found that there was some transport of

larvae within the Bay via the residual currents but that

most of the larvae either remained in, or were returned to,

the area of major spawning. They were further able to

demonstrate that although there was larval dispersal

beyond the Bay of Fundy, no large-scale exchange

between Georges Bank and the Scotian Shelf occurred.

There is considerable uncertainty about the

mechanisms involved in recruitment to the Mid-Atlantic

region. Densities and distributions of scallops in the

Hudson Canyon and sections off the Virginia Capes and

Cape Hatteras are variable. It is thought that beds in

productive areas, such as the New York Bight, may not be

self-sustaining, but may supply recruits for beds located

further down-current (i.e., to the south). The occasional

heavy recruitment to the Middle Atlantic may be the result

of periodically occurring optimal reproductive conditions,

or augmented recruitment from spawning on Georges

Bank, when years of loose gyrals may result in much of

the spawn being swept away to these more southerly areas

(Shumway et al., in prep.). Because of this variability and

the fact that the spawn from southern populations is

normally swept away from the parent population, these

populations are not self-sustaining and the fishery in these

areas varies from year to year.

It is not known if the beds on the coast of Maine or in

deeper waters of the Gulf of Maine are self-sustaining.
Page 2

SPAT

At the end of their pelagic existence, the larvae enter

the pediveliger stage with the development of a foot and

secreting threads (byssus) which are used to attach to hard

surfaces (Culliney 1974). Spatfall (the settling of larval

scallops to the bottom), and the period immediately

following, is thought to be a time that is particularly

important in the formation of scallop beds (Posgay 1953)

and in determining year class size (Bourne 1965; Caddy

1975). Settlement is assumed to occur by mid-December

(Thouzeau et al. 1991a). The transition from freeswimming to the benthos at a size of about 0.25 mm is

accompanied by drastic changes in diet, morphology, and

locomotory ability and it is conceivable that mortality may

be as high during natural settlement as when spat are

reared artificially (Bourne 1965; Culliney 1974).

Merrill and Edwards (1976) noted that when scallop

spat settle they are extremely delicate and do not survive

on shifting sand bottoms. Those that land on sedentary

branching plants and animals or any other hard surface on

or above the ocean floor which offers freedom of shell

movement on all sides may have a distinct survival

advantage (Larsen and Lee 1978).

The availability of suitable surfaces on which to settle

seems to be a primary requirement for successful scallop

reproduction. Larvae show a thigmotactic settling

response to shell fragments and small pebbles; settlement

occurs predominantly on the undersides of these objects

(Caddy 1968; Culliney 1974). Spat also settle on

navigation buoys (Merrill and Edwards 1976), on the red

alga Rhodomela conferroides (Naidu 1970), on hydroids

such as Hydrallmania, and on the tubes made by

amphipods (Larsen and Lee 1978). Spat settlement varies

significantly with depth and water turbulence: numbers of

spat generally increase with increasing depth, but this

relationship is less evident with increasing water

turbulence (Pearce et al. 1998).

A close association between the bryozoan, Eucratea

loricata (= Gemelleria of Baird 1953), and larval scallops

has been reported. Eucratea attach to adult scallops, and

have been found to contain large numbers of 2-5 mm

immature scallops (Baird 1953; Caddy 1972). These

scallops detach themselves from the bryozoan when about

4-5 mm and then attach themselves to the shells of larger

scallops (Dow 1956).

Pediveligers appear to be able to delay

metamorphosis for up to one month until suitable physical

substrates for settlement are encountered; however, the

effects of this delay on the scallops is not known (Culliney

1974).

JUVENILES AND ADULTS

During the second growing season, juvenile scallops

(5-12 mm) leave the original substrate on which they

settled and attach themselves to shells and bottom debris

by byssus (Dow and Baird 1960). As young sea scallops

age, they become less mobile and show less tendency to

attach to the bottom using byssal threads (Caddy 1972;

MacKenzie 1979). The frequency of byssal thread

production also decreases with age (Caddy 1972). The

maximum size for frequent byssal attachment and

swimming was found to be 110 mm (5-6 yrs old).

Scallops are relatively active until they are about 80

mm long, swimming in response to disturbances, such as

predation (Baird 1954) and commercial dredging (Caddy

1968). While swimming, young scallops can also be

carried long distances by currents (Baird 1954).

There is no evidence of mass migrations by scallops.

The movements of sea scallops are usually localized and

random or current-assisted. Numerous tagging

experiments have shown that once aggregations of adults

are formed, they remain fixed (Baird 1954; Dickie 1953;

Naidu 1970; Schick 1979). Posgay (1981) reported that

tagged scallops came primarily from downcurrent areas on

Georges Bank. While 80% of the tagged returns had

traveled < 3 km and 97% had traveled < 16 km, a few

individuals were reported to have traveled more than 48

km in 2+ years. Melvin et al. (1985) reported primarily

circular movements of tagged scallops on Georges Bank

corresponding to the clockwise gyre on the Bank (Figure

3), and while 85% of the tagged returns had moved < 15

km, several had moved > 50 km.

REPRODUCTION

The sexes in sea scallops are separate and can be

distinguished by their color as the gonads ripen prior to

spawning. Hermaphroditism is known to occur, but is not

common (e.g., Merrill and Burch 1960; Worms and

Davidson 1986). Mature gametes have been seen in

females as young as one year (Langton et al. 1987) and

scallops have been reported to spawn after their first

growth ring has formed (25-35 mm shell height) (Naidu

1970; MacKenzie 1979). However, most sea scallops do

not become sexually mature until the spring of their third

year (about 75 mm; Posgay 1982).

Egg number is directly related to shell height and

maximum egg production is not reached until several

years after maturity. It is estimated that scallops produce

1-270 million eggs per individual (Langton et al. 1987);

by age 4 (85-90 mm) a female will release about two

million eggs. Gonad output (egg number) is greater in

scallops from shallow water (10-20 m), where the food

supply is greater and temperatures are higher, than in

scallops from deep water (170-180 m) (MacDonald and

Thompson 1986; MacDonald et al. 1987; Barber et al.

1988). There is evidence of latitudinal differentiation in

fecundity. For example, MacDonald and Thompson

(1988) found that scallops from New Jersey are more

fecund that those from locations further north, although
Page 3

variation along a depth gradient on a microgeographic

scale may be as great or greater than variation on

latitudinal scale (MacDonald and Thompson 1985a;

1985b; 1988).

Shumway et al. (1988) summarized the gametogenic

cycle of sea scallops from Maine as follows. During

January, gametogenesis has already reached the early

developmental stage; energy reserves are at their lowest

level (Robinson et al. 1981), and energy must be

mobilized from the accumulated reserves. During spring,

gametogenesis is underway, gonad size increases, feeding

begins with coincidental spring phytoplankton blooms and

energy reserves begin to accumulate. During summer

(June-August), food is plentiful, gametes are ripening and

energy is derived from spring storage and from food

intake (Robinson et al. 1981). Spawning takes place in

September/October and the animals enter a reproductively

quiescent or rest period. Barber et al. (1988) found that

primary oogenesis in sea scallops from Boothbay Harbor,

Maine, was initiated in February, secondary oogenesis in

March and vitelogenesis after June. Spawning and

reabsorption of mature ova was evident in September and

to a greater extent in October, after which the animals

were in a period of recovery (December/January).

Spawning generally occurs synchronously when the

males extrude sperm and the females release eggs en

masse into the water, but it may occur over a more

protracted period of time depending on environmental

conditions. It has been suggested that year-class strength

may correlate with the degree of spawning synchrony,

rather than fecundity per se (egg number) (Langton et al.

1987).

There is a major annual spawning period in the late

summer to fall (August to October) (Parsons et al. 1992a)

although spring or early summer (June-July) spawning

also occurs at specific locations. The timing of spawning

can vary with latitude, starting in summer in southern

areas and in fall in the northern areas. For example,

MacKenzie et al. (1978) reported that off the coast of

North Carolina and Virginia, spawning generally occurred

as early as July and that further north on the Mid-Atlantic

shelf spawning occurred in August. However, there are

exceptions to this pattern. MacDonald and Thompson

(1988) report that scallops off of New Jersey spawned up

to two months later than scallops from Newfoundland

(September-November versus late August-early

September). They found no clearly identifiable latitudinal

trends in the timing of spawning.

More recently, however, researchers have discovered

a biannual spawning cycle on the Mid-Atlantic shelf south

of the Hudson Canyon, with spawning occurring both in

the spring and fall (DuPaul et al. 1989; Schmitzer et al.

1991; Davidson et al. 1993). Kirkley and DuPaul (1991)

found that the spring spawning event in the Mid-Atlantic

is the more predictable and dominant spawning event, and

that fall spawning is minor and temporally irregular,

sometimes not occurring at all. Schmitzer et al. (1991)

also reported that the spring spawning was of longer

duration and the scallops showed greater fecundity than in

the fall.

North of the Hudson Canyon there is generally a

single annual spawning event starting in late summer or

early fall. However, there are some reports of biannual

spawning (spring and fall) in the Gulf of Maine and

Georges Bank, with the fall spawning being dominant

(Barber et al. 1988; DiBacco et al. 1995). On Georges

Bank fall spawning generally occurs in late September or

early October (Posgay and Norman 1958; MacKenzie et

al. 1978; McGarvey et al. 1992; DiBacco et al. 1995). In

Cape Cod Bay, spawning occurs in late September and

early October (Posgay 1950). In the Gulf of Maine

spawning occurs in August and September (Drew 1906;

Welch 1950; Baird 1953; Culliney 1974; Robinson et al.

1981; Barber et al. 1988). In the Bay of Fundy the

spawning period extends from late July to November

(Stevenson 1936; Dickie 1955; Beninger 1987;

MacDonald and Thompson 1988; Dadswell and Parsons

1992).

Scallops beds generally spawn synchronously in a

short time, going from completely ripe to completely

spent in less than a week (Posgay and Norman 1958;

Posgay 1976). “Dribble spawning” (periodic pulsed

spawning) has been reported in scallops from

Newfoundland coastal waters (Naidu 1970) and possibly

New Jersey in June and July (MacDonald and Thompson

1988). A rapid temperature change, the presence in the

water of sperm from other scallops, agitation, or tides may

trigger scallop spawning (Parsons et al. 1992a).

FOOD HABITS

Sea scallops are suspension or filter feeders, using

currents created by short hairs (cilia) on the gills to move

and filter water containing suspended particulate material.

The principal food is phytoplankton, diatoms, and

microscopic animals (such as peridinians, tintinnids,

ciliate protozoa), but detrital particles (pieces of dead

organic matter) and associated bacteria can also contribute

to energy gain during periods of low phytoplankton

concentrations (Bordon 1928; Stevenson 1936; Shumway

et al. 1987; Grant and Cranford 1991). Dissolved organic

matter (absorbed through the tissues) has been suggested

to be an additional minor source of nutrition, particularly

for scallop larvae (Marshall and Lee 1991).

Elevated concentrations of inorganic suspended

material and clay-sized particles can interfere with scallop

feeding, but the presence of low concentrations (< 0.5

mg/L) of inorganic particulate matter in the diet may be

important in enabling sea scallops to utilize phytoplankton

cells efficiently (Cranford and Gordon 1992).

Components of the diet vary in abundance depending

on the geographic location of the bed. Sea scallops in

coastal areas and bays encounter more seaweed and
Page 4

seagrass detritus and may be exposed periodically to

significant amounts of resuspended inorganic material.

Offshore scallops feed mainly on phytoplankton and

resuspended organic material. Phytoplankton appear to be

necessary for meeting scallop energy demands, although

seaweed detritus may be an important food supplement in

nearshore environments (Grant and Cranford 1991).

Shumway et al. (1987) reported on the seasonal

changes in the gut contents of sea scallops. Two

populations were compared, one in shallow water (20 m

depths) and the other in deep water (180 m). A total of 27

species of algae, ranging in size from 10-350 μm were

identified, plus a number of miscellaneous items including

pollen grains, ciliates, zooplankton tests, and considerable

detrital material and bacteria. The benthic and pelagic

food species were equally represented in the shallow

water population; however, benthic species outnumbered

pelagic species in the deep water population. Seasonal

variations in occurrence of food items were found and

these coincided with bloom periods for the individual

algal species. The gut contents generally reflected the

available organisms in the surrounding habitat and it was

concluded that sea scallops are opportunistic filter feeders

which take advantage of both benthic and pelagic food.

GROWTH

Growth rates show considerable variation among

populations. Some of the highest growth rates have been

observed on Georges Bank and in Port-au-Port Bay

(Stewart and Arnold 1994). Scallops from the Gulf of St.

Lawrence generally have slower growth rates than Gulf of

Maine and Bay of Fundy scallops (Chouinard and

Mladenov 1991). Growth rates have been shown to be

positively correlated to water temperature and food

availability, and negatively related to depth, latitude, and

age.

Larval growth rates of 3.1-3.5 μm/day (Gallager et al.

1996) and 4.3-4.8 μm/day (Manuel et al. 1996b) have

been reported in mesocosm studies. Culliney (1974)

reported that development to straight-hinge veliger took 4

days at 12-18o

C, development to pediveliger took 28 days

at 15o

C, and settlement occurred in 35 days. The duration

of the larval stage on Georges Bank is 40-60 days

(Thouzeau et al. 1991a). Wildish and Saulnier (1992)

reported juvenile growth rates of 0.047-0.199 mm/day at

1.2-7.6o

C, and adult growth rates of 0.02-0.121 mm/day in

the laboratory.

PREDATION

Scallop larvae are planktonic, thus they are

potentially preyed upon by filter feeders and planktonic

carnivores (Langton and Robinson 1990).

Teleost predators of juvenile scallops include cod

(Medcof and Bourne 1964), wolffish (Medcof and Bourne

1964; Nelson and Ross 1992), ocean pout (Bigelow and

Schroeder 1953), sculpins (Caddy 1968; 1973), American

plaice (Medcof and Bourne 1964; Naidu and Meron 1986;

Robert et al. 1986), winter flounder (Caddy 1968, 1973),

yellowtail flounder (Naidu and Meron 1986), and eel pout

(Bigelow and Schroeder 1953). Crabs and lobsters may

also prey on scallops (Elner and Jamieson 1979).

Medcof and Bourne (1964) reported that small

juveniles were ingested whole by the sun starfish

Crossaster papposus. Naidu and Scalpen (1976) reported

that juvenile starfish, Asterias vulgaris, were the principal

predators of scallop spat in spat traps in Newfoundland.

HABITAT CHARACTERISTICS

The habitat characteristics of sea scallops are

summarized in Table 1. This information concentrates

primarily on beds in U.S. water; most information on beds

north of the Bay of Fundy was not considered.

LARVAE

In laboratory studies, larvae were viable at

temperatures of 12-18o

C (mass mortalities occurred at

higher temperatures), and at salinities as low as 10.5 ppt,

although salinities ranging from 16.9-30 ppt are preferred

(Culliney 1974). In nature, larvae settle on gravelly sand

which may contain shell fragments (Langton and

Robinson 1990), and often actively select substrates

covered with a biofilm (Parsons et al. 1993). Prior to

settlement, larvae circulate with residual currents ranging

from 6-25 cm/s and tend to concentrate in the upper 10 m

of the water column (Tremblay and Sinclair 1990a;

Parsons et al. 1992b).

JUVENILES

In laboratory studies, juveniles have been maintained

successfully at 1.2-15o

C (Manuel and Dadswell 1991;

Wildish and Saulnier 1992; Barbeau and Scheibling

1994b; Kleinman et al. 1996). The optimal current

velocity for feeding and growth has been shown to be 10

cm/s; currents stronger than 10 cm/s inhibit feeding

(Wildish and Saulnier 1992). Stronger currents may be

experienced in nature (e.g., up to 25 cm/s in

Passamaquoddy Bay), but these can be avoided by feeding

during periods of slack water (i.e., low and high tide). In

nature juveniles are found mainly on gravel, small rocks,

shells and silt (Thouzeau et al. 1991a; Parsons et al.

1992b), and maximum densities of juveniles on Georges

Bank have been found at depths of 62-91 m (Thouzeau et

al. 1991a).
Page 5

ADULTS

Adults experience optimal growth at temperatures of

10-15o

C; temperatures above 21oC are lethal (Stewart and

Arnold 1994); spawning occurs at 9.0-11.2o

C (MacKenzie

et al. 1978). They prefer full strength seawater and

salinities of 16.5 ppt or lower are lethal (Stewart and

Arnold 1994). Adults are generally found on coarse

substrate, usually gravel, shells and rock (MacKenzie et

al. 1978; Langton and Robinson 1990; Thouzeau et al.

1991a; Stewart and Arnold 1994), in areas with at least

some water movement (optimal growth occurs at 10

cm/s), which is critical for feeding, oxygen and removal of

waste (Wildish and Saulnier 1992; Stewart and Arnold

1994). They are typically found at depths ranging from

18-110 m (MacKenzie et al. 1978; Serchuk et al. 1982;

Naidu and Anderson 1984; Stewart and Arnold 1994), but

tend to be found shallower in more northern populations

(e.g., 2 m in estuaries and embayments along the coast of

Maine).

GEOGRAPHICAL DISTRIBUTION

The sea scallop is distributed on the Atlantic

continental shelf of North America from the north shore of

the Gulf of St. Lawrence to Cape Hatteras, North Carolina

(Stewart and Arnold 1994). In the United States, sea

scallops are located on Georges Bank, in the MidAtlantic, and in the Gulf of Maine.

Sea scallops typically occur at depths ranging from

18-110 m, but they may also occur in waters as shallow as

2 m in estuaries and embayments along the Maine coast

(Serchuk et al. 1982; Naidu and Anderson 1984). In

southern areas they are rarely found at depths less than 55

m (Squires 1962), primarily due to temperature variation

with depth (Bourne 1965). Although sea scallops are

rarely found deeper than about 110 m, some deep-water

populations have been found as deep as 384 m (Merrill

1959); deep-water populations at 170 to 180 m have been

reported in the Gulf of Maine (Barber et al. 1988).

Sea scallops often occur in dense aggregations called

beds. Beds may be sporadic (perhaps lasting for a few

years) or essentially permanent (e.g., commercial beds

supporting the Georges Bank fishery) (Figure 4). The

highest concentration of many permanent beds appears to

correspond to areas of suitable temperatures, food

availability, substrate, and where physical oceanographic

features such as fronts and gyres may keep larval stages in

the vicinity of the spawning population (Thouzeau et al.

1991a, b; Tremblay and Sinclair 1992).

EGGS AND LARVAE

Eggs and larvae are not enumerated by the Northeast

Fisheries Science Center (NEFSC) Marine Resources

Monitoring, Assessment and Prediction (MARMAP)

program (P. Berrien, NMFS, NEFSC, Highlands, NJ,

personal communication). Until recently sea scallop

larvae could not even be identified in the wild (Tremblay

et al. 1987).

However, the NOAA Estuarine Living Marine

Resources (ELMR) program has identified the presence of

eggs and larvae in a number of New England bays and

estuaries (Table 2; Jury et al. 1994).

JUVENILES AND ADULTS

Summer NEFSC sea scallop surveys collected

scallops from Georges Bank to Cape Hatteras (Figure 5).

The Gulf of Maine was not surveyed. From New Jersey

to Cape Hatteras scallops were concentrated along the

edge of the continental shelf. Scallops were concentrated

further inshore from the Hudson Canyon north to Long

Island and in the Great South Channel. Scallops were

found throughout Georges Bank; however, central

Georges Bank near Cultivator Shoals (where density is

known to be low) was not sampled. Highest densities were

found in the northeastern area of Georges Bank, an area

that traditionally provides the largest harvests and is the

most valuable sea scallop fishery (MacKenzie et al. 1978;

Serchuk et al. 1979; Posgay 1981).

The NOAA ELMR program has identified the

presence of juvenile and adult sea scallops in a number of

New England bays and estuaries (Table 2; Jury et al.

1994). They are listed as ‘abundant’ within the Gulf of

Maine.

In the Gulf of Maine, non-stratified surveys and data

from commercial catches indicate scallop beds occur in

inshore areas from Penobscot Bay and eastward, as well

as in Cape Cod Bay. Offshore beds occur at Jeffreys

Basin, Cashes Ledge, Fippinnies Ledge, Jeffreys Ledge,

near Three-Dory Ridge, Toothaker Ridge, off Jonesport

and Machias bays, and Stellwagen Bank (Serchuk and

Rak 1983; Serchuk and Wigley 1984). The largest

catches in the Gulf of Maine have traditionally occurred

on Jeffreys Ledge and Fippinnies Ledge (Serchuk and Rak

1983; Serchuk and Wigley 1984).

STATUS OF THE STOCKS

Total commercial sea scallop landings (U.S. and

Canada) peaked at 26,671 metric tons (mt of meat) in

1978, declined to 9,781 mt in 1984, increased to 22,831

mt in 1991, but dropped back down to 9,822 mt in 1995

(Northeast Fisheries Science Center 1997). The total U.S.

landings peaked in 1990 at 17,174 mt, but dropped to

7,300 mt in 1993, and have remained at comparable levels

through 1995 (Murawski and Wigley 1995; Northeast

Fisheries Science Center 1997).

Total landings from Georges Bank declined to 9,900
Page 6

mt in 1993, 32% lower than the 1992 total of 14,600

(Murawski and Wigley 1995), and to 2,991 mt in 1995,

the lowest in the 1957-1995 period (Northeast Fisheries

Science Center 1997). U.S. Georges Bank landings

decreased 90% from 1990 (9,982 mt) to 1994 (1,140 mt)

as a result of several years of poor recruitment and

redirection of vessel effort toward the Mid-Atlantic region

(Northeast Fisheries Science Center 1997; Figure 6). In

1995, landings remained about the same as in 1994, due at

least in part to area closures in December 1994 (Northeast

Fisheries Science Center 1997), but landings increased to

2,180 mt in 1996, a 120% increase over 1995 (Lai and

Rago 1998). Relative abundance indices dropped to their

lowest level in 1993, but rebounded to median levels in

1996 (Northeast Fisheries Science Center 1997; Figure 6).

This is probably a result of area closures on the Bank.

U.S. landings from the Gulf of Maine in 1993 were

800 mt, 10% higher than in 1991 (Murawski and Wigley

1995), dropped to 525 mt by 1994 and have increased to

715 mt in 1996 (Lai and Rago 1998; Figure 6).

U.S. landings from the Mid-Atlantic Bight averaged

6,000 mt in 1994 and 1995, about twice as high as 1993

landings, and were primarily driven by the strong 1990

and 1991 year classes (Northeast Fisheries Science Center

1997; Figure 6). Landings dropped to 4,677 mt in 1996, a

23% decrease from 1995 (Lai and Rago 1998). Relative

abundance indices increased between 1992 and 1995 but

decreased substantially from 1995 to 1996 (Northeast

Fisheries Science Center 1997; Figure 6).

The September 1997 report to Congress, ‘Status of

Fisheries of the United States’ (National Marine Fisheries

Service 1997), states that the Atlantic sea scallop is

currently in an overfished condition.

RESEARCH NEEDS

Our literature search uncovered substantial

information on the biology of the giant sea scallop.

However, more information on the genetic differentiation

of scallop populations is needed to better understand

recruitment and stock structure in the species. Previous

studies of population discrimination have used

morphometric or allozyme analyses; Zouros and GartnerKepay (1985) found no significant allozyme

differentiation among 10 scallop populations near Nova

Scotia. However, current techniques for examining

genetic differentiation are much more powerful, and

genetic markers which could potentially be very useful for

studying the genetic structure of sea scallop populations

have recently been developed (e.g., microsatellite DNA:

Manuel et al. 1996a; Gjetvaj et al. 1997; Herbinger et al.

1998; random amplified polymorphic DNA: Patwary et al.

1994).

Existing information on recruitment processes (i.e.,

which beds are self-sustaining and which are not) is rather

vague. Relatively little information exists since the

identification of planktonic sea scallop larvae in the wild

was not possible until quite recently (Tremblay et al.

1987). New genetic techniques (see above) make it

possible to track the movement of larvae, providing very

detailed information about recruitment processes (e.g.,

Manuel et al. (1996a) used a microsatellite DNA probe to

distinguish the population of origin of veliger larvae in a

large mesocosm).

Better information on the effect of environmental

variables on growth, survival, and production is needed.

Current information is restricted for the most part to EFH

levels 1 and 2, although some level 3 data exist, e.g., there

is some evidence of fecundity and growth rate differences

with depth (or temperature). There is almost no

information on the scallop egg stage in the wild; what is

known is restricted to morphometrics (i.e., egg sizes) and

fecundity. More data on the duration of the egg stage,

mortality rates, predation, and substrate effects are

needed.

ACKNOWLEDGMENTS

The authors thank Eric Weissberger for help with the

literature review, Christine Zetlin for producing the

NEFSC survey map, Cathy Noonan for editorial

comments, and Claire Steimle, Judy Berrien, and Rande

Ramsey-Cross for library assistance.

REFERENCES CITED

Baird, F.T., Jr. 1953. Observations on the early life

history of the giant scallop (Pecten magellanicus).

Maine Dep. Sea Shore Fisheries Res. Bull. 14: 1-7.

Baird, F.T. 1954. Migration of the deep sea scallop

(Pecten magellanicus). Maine Dep. Sea Shore Fish.

Circ. 14. 8 p.

Barbeau, M.A. and R.E. Scheibling. 1994a. Behavioral

mechanisms of prey size selection by sea stars

(Asterias vulgaris, Verrill) and crabs (Cancer

irroratus, Say) preying on juvenile sea scallops

(Placopecten magellanicus (Gmelin)). J. Exp. Mar.

Biol. Ecol. 180: 103-136.

Barbeau, M.A. and R.E. Scheibling. 1994b. Temperature

effects on predation of juvenile sea scallops

[Placopecten magellanicus (Gmelin)] by sea stars

(Asterias vulgaris Verrill) and crabs (Cancer

irroratus Say). J. Exp. Mar. Biol. Ecol. 182: 27-47.

Barber, B.J., R. Getchell, S. Shumway, and D. Schick.

1988. Reduced fecundity in a deep-water population

of the giant scallop Placopecten magellanicus in the

Gulf of Maine, USA. Mar. Ecol. Prog. Ser. 42: 207-

212.

Beninger, P.G. 1987. A qualitative and quantitative study

of the reproductive cycle of the giant scallop,
Page 7

Placopecten magellanicus, in the Bay of Fundy (New

Brunswick, Canada). Can. J. Zool. 65: 495-498.

Bigelow, H.B. and W.C. Schroeder. 1953. Fishes of the

Gulf of Maine. U.S. Fish Wildl. Serv. Fish. Bull. 53.

577 p.

Bordon, M.A. 1928. A contribution to the study of the

giant scallop, Placopecten grandis (Solander). Fish.

Res. Board Can. Manuscr. Rep. Biol. Stn., No. 350.

27 p.

Bourne, N. 1965. A comparison of catches by 3- and 4-

inch rings on offshore scallop drags. J. Fish. Res.

Board Can. 22: 313-333.

Caddy, J.F. 1968. Underwater observations on scallop

(Placopecten magellanicus) behaviour and drag

efficiency. J. Fish. Res. Board Can. 25: 2123-2141.

Caddy, J.F. 1972. Progressive loss of byssus attachment

with size in the sea scallop, Placopecten

magellanicus (Gmelin). J. Exp. Mar. Biol. Ecol. 9:

179-190.

Caddy, J.F. 1973. Underwater observations on tracks of

dredges and trawls and some effects of dredging on a

scallop ground. J. Fish. Res. Board Can. 30: 173-180.

Caddy, J.F. 1975. Spatial model for an exploited shellfish

population, and its application to the Georges Bank

scallop fishery. J. Fish. Res. Board Can. 32: 1305-

1328.

Chouinard, G.A. and P.V. Mladenov. 1991. Comparative

growth of the sea scallop (Placopecten magellanicus)

in the southern Gulf of St. Lawrence. In J.C.

Therriault ed. The Gulf of St. Lawrence: Small ocean

or big estuary? Symposium on the Oceanography and

Fishery of the Gulf of St. Lawrence, Mont-Joli,

Quebec (Canada), 14 Mar. 1989. Can. Spec. Publ.

Fish. Aquat. Sci. 113: 261-267.

Cranford, P.J., C.W. Emerson, B.T. Hargrave, and T.G.

Milligan. 1998. In situ feeding and absorption

responses of sea scallops Placopecten magellanicus

(Gmelin) to storm-induced changes in the quantity

and composition of the seston. J. Exp. Mar. Biol.

Ecol. 219: 45-70.

Cranford, P.J. and D.C. Gordon, Jr. 1992. The influence

of dilute clay suspensions on sea scallop

(Placopecten magellanicus) feeding activity and

tissue growth. Netherlands J. Sea Res. 30: 107-120.

Culliney, J.L. 1974. Larval development of the giant

scallop Placopecten magellanicus (Gmelin). Biol.

Bull. (Woods Hole) 147: 321-332.

Dadswell, M.J. and G.J. Parsons. 1992. Exploiting lifehistory characteristics of the sea scallop, Placopecten

magellanicus (Gmelin, 1791), from different

geographical locations in the Canadian Maritimes to

enhance suspended culture grow-out. J. Shellfish Res.

11: 299-305.

Davidson, L.-A., M. Lanteigne, and M. Niles. 1993.

Timing of the gametogenic development and

spawning period of the giant scallop Placopecten

magellanicus (Gmelin) in the southern Gulf of St.

Lawrence. Can. Tech. Rep. Fish. Aquat. Sci. 1935. 14

p.

DiBacco, C., G. Robert, and J. Grant. 1995. Reproductive

cycle of the sea scallop, Placopecten magellanicus

(Gmelin, 1791), on northeastern Georges Bank. J.

Shellfish Res. 14: 59-69.

Dickie, L.M. 1953. Fluctuations in abundance of the giant

scallop, Placopecten magellanicus (Gmelin), in the

Digby area of the Bay of Fundy. Fish. Res. Board

Can. Manuscr. Ser. Rep. Biol. Stn., No. 526. 148 p.

Dickie, L.M. 1955. Fluctuations in abundance of the giant

scallop, Placopecten magellanicus (Gmelin), in the

Digby area of the Bay of Fundy. J. Fish. Res. Board

Can. 12: 797-857.

Dow, R.L. 1956. The Maine sea scallop fishery. Maine

Dep. Sea Shore Fisheries, Fish. Circ. 19. 8 p.

Dow, R.L. and F.T. Baird, Jr. 1960. Scallop resources of

the United States Passamaquoddy area. U.S. Fish.

Wildl. Serv. Spec. Sci. Rep., Fish. No. 367. 9 p.

Drew, G.A. 1906. The habits, anatomy and embryology of

the giant scallop (Pecten tenuicostatus Mighels).

Univer. Maine Stud. 6. 71 p.

DuPaul, W.D., J.E. Kirkley, and A.C. Schmitzer. 1989.

Evidence of a semiannual reproductive cycle for the

sea scallop, Placopecten magellanicus (Gmelin,

1791), in the mid-Atlantic region. J. Shellfish Res. 8:

173-178.

Elner, R.W. and G.S. Jamieson. 1979. Predation of sea

scallops, Placopecten magellanicus, by the rock crab,

Cancer irroratus, and the American lobster, Homarus

americanus. J. Fish. Res. Board Can. 36: 537-543.

Gallager, S.M., J.L. Manuel, D.A. Manning, and R.

O’Dor. 1996. Ontogenetic changes in the vertical

distribution of giant scallop larvae, Placopecten

magellanicus, in 9-m deep mesocosms as a function

of light, food, and temperature stratification. Mar.

Biol. 124: 679-692.

Gjetvaj, B. R.M. Ball, S. Burbridge, C.J. Bird, E.

Kenchington, and E. Zouros. 1997. Amounts of

polymorphism at microsatellite loci in the sea scallop

Placopecten magellanicus. J. Shellfish Res. 16: 547-

553.

Grant, J. and P.J. Cranford. 1991. Carbon and nitrogen

scope for growth as a function of diet in the sea

scallop Placopecten magellanicus. J. Mar. Biol.

Assoc. U.K. 71: 437-450.

Herbinger, C.M., B.M. Vercaemer, B. Gjetvaj, and R.K.

O’Dor. 1998. Absence of genetic differentiation

among geographically close sea scallop (Placopecten

magellanicus G.) beds with cDNA and microsatellite

markers. J. Shellfish Res. 17: 117-122.

Hurley, G.V., M.J. Tremblay, and C. Couturier. 1986.

Daily growth increments in the shells of larval sea

scallops (Placopecten magellanicus). Northwest Atl.

Fish. Organ. (NAFO) Sci. Counc. Res. Doc. 86/99.

11 p.

Jury, S.H., J.D. Field, S.L. Stone, D.M. Nelson, and M.E.
Page 8

Monaco. 1994. Distribution and abundance of fishes

and invertebrates in North Atlantic estuaries. ELMR

Rep. No. 13. NOAA/NOS Strategic Environmental

Assessments Division, Silver Spring, MD. 221 p.

Karney, R.C. 1996. Hatchery culture techniques for the

giant sea scallop Placopecten magellanicus

(Abstract). J. Shellfish Res. 15: 455-456.

Kirkley, J.E. and W.D. DuPaul. 1991. Temporal

variations in spawning behavior of sea scallops,

Placopecten magellanicus (Gmelin, 1791), in the

Mid-Atlantic resource area. J. Shellfish Res. 10: 389-

394.

Kleinman, S., B.G. Hatcher, and R.E. Scheibling. 1996.

Growth and content of energy reserves in juvenile sea

scallops, Placopecten magellanicus, as a function of

swimming frequency and water temperature in the

laboratory. Mar. Biol. 124: 629-635.

Lai, H. and P. Rago. 1998. Sea scallops. In S.H. Clark ed.

Status of the fishery resources off the northeastern

United States for 1998. p. 131-133. NOAA Tech.

Mem. NMFS-NE-115.

Langton, R.W. and W.E. Robinson. 1990. Faunal

associations on scallop grounds in the western Gulf of

Maine. J. Exp. Mar. Biol. Ecol. 144: 157-171.

Langton, R.W., W.E. Robinson, and D. Schick. 1987.

Fecundity and reproductive effort of sea scallops

Placopecten magellanicus from the Gulf of Maine.

Mar. Ecol. Prog. Ser. 37: 19-25.

Larsen, P.F. and R.M. Lee. 1978. Observations on the

abundance, distribution and growth of post-larval sea

scallops, Placopecten magellanicus, on Georges

Bank. Nautilus 92: 112-116.

MacDonald, B.A. and R.J. Thompson. 1985a. Influence

of temperature and food availability on the ecological

energetics of the giant scallop Placopecten

magellanicus. I. Growth rates of shell and somatic

tissue. Mar. Ecol. Prog. Ser. 25: 279-294.

MacDonald, B.A. and R.J. Thompson. 1985b. Influence

of temperature and food availability on the ecological

energetics of the giant scallop Placopecten

magellanicus. II. Reproductive output and total

production. Mar. Ecol. Prog. Ser. 25: 295-303.

MacDonald, B.A. and R.J. Thompson. 1986. Influence of

temperature and food availability on the ecological

energetics of the giant scallop Placopecten

magellanicus. III. Physiological ecology, the

gametogenic cycle and scope for growth. Mar. Biol.

93: 37-48.

MacDonald, B.A. and R.J. Thompson. 1988. Intraspecific

variation in growth and reproduction in latitudinally

differentiated populations of the giant scallop

Placopecten magellanicus (Gmelin). Biol. Bull.

(Woods Hole) 175: 361-371.

MacDonald, B.A., R.J. Thompson and B.L. Bayne. 1987.

Influence of temperature and food availability on the

ecological energetics of the giant scallop Placopecten

magellanicus. IV. Reproductive effort, value and

cost. Oecologia (Berl.) 72: 550-556.

MacKenzie, C.L., Jr. 1979. Biological and fisheries data

on sea scallop, Placopecten magellanicus (Gmelin).

U.S. Natl. Mar. Fish. Serv. Northeast Fish. Cent.

Sandy Hook Lab. Tech. Ser. Rep. No. 19. 34 p.

MacKenzie, C.L., Jr., A.S. Merrill, and F.M. Serchuk.

1978. Sea scallop resources off the northeastern U.S.

coast, 1975. Mar. Fish. Rev. 40(2): 19-23.

Manuel, J.L. and M.J. Dadswell. 1991. Swimming

behavior of juvenile giant scallop, Placopecten

magellanicus, in relation to size and temperature.

Can. J. Zool. 69: 2250-2254.

Manuel, J.L. and M.J. Dadswell. 1993. Swimming of

juvenile sea scallops, Placopecten magellanicus

(Gmelin): a minimum size for effective swimming? J.

Exp. Mar. Biol. Ecol. 174: 137-175.

Manuel, J.L., C.M. Pearce, and R.K. O’Dor. 1997.

Vertical migration for horizontal transport while

avoiding predators: II. Evidence for the tidal/diel

model from two populations of scallop (Placopecten

magellanicus) veligers. J. Plankton Res. 19: 1949-

1973.

Manuel, J.L., S. Burbridge, E.L. Kenchington, M. Ball,

and R.K. O’Dor. 1996a. Veligers from two

populations of scallop Placopecten magellanicus

exhibit different vertical distributions in the same

mesocosm. J. Shellfish Res. 15: 251-257.

Manuel, J.L., S.M. Gallager, C.M. Pearce, D.A. Manning,

and R.K. O’Dor. 1996b. Veligers from different

populations of sea scallop Placopecten magellanicus

have different vertical migration patterns. Mar. Ecol.

Prog. Ser. 142: 147-163.

Marshall, C.T. and K. Lee. 1991. Uptake of dissolved

glycine by sea scallop Placopecten magellanicus

(Gmelin, 1791) larvae. In S.E. Shumway and P.A.

Sandifer eds. An international compendium of scallop

biology and culture: a tribute to James Mason. p. 60-

66. World Aquaculture Society, Baton Rouge, LA.

McGarvey, R., F.M. Serchuk, and I.A. McLaren. 1993.

Spatial and parent-age analysis of stock-recruitment

in the Georges Bank sea scallop (Placopecten

magellanicus) population. Can. J. Fish. Aquat. Sci.

50: 564-574.

McGarvey, R., F.M. Serchuk, and I.A. McLaren. 1992.

Statistics of reproduction and early life history

survival of the Georges Bank sea scallop

(Placopecten magellanicus) population. J. Northwest

Atl. Fish. Sci. 13: 83-99.

Medcof, J.C. and N. Bourne. 1964. Causes of mortality of

the sea scallop, Placopecten magellanicus. Proc. Nat.

Shellfish Assoc. 53: 33-50.

Melvin, G.D., M.J. Dadswell, and R.A. Chandler. 1985.

Movements of scallops Placopecten magellanicus

(Gmelin, 1791) (Mollusca: Pectinidae) on Georges

Bank. Can. Atl. Fish. Sci. Adv. Comm. Res. Doc.

85/30. 29 p.

Merrill, A.S. 1959. A comparison of Cyclopecten nanus
Page 9

(Verrill and Bush) and Placopecten magellanicus

(Gmelin). Harvard University Museum of

Comparative Zoology. Occas. pap. on Molluscs. 2:

209-228.

Merrill, A.S. and J.B. Burch. 1960. Hermaphroditism in

the sea scallop, Placopecten magellanicus (Gmelin).

Biol. Bull. (Woods Hole) 119: 197-201.

Merrill, A.S. and R.L. Edwards. 1976. Observations on

molluscs from a navigation buoy with special

emphasis on the sea scallop Placopecten

magellanicus. Nautilus 90: 54-61.

Mullen, D.M. and J.R. Moring. 1986. Species profiles:

Life histories and environmental requirements of

coastal fishes and invertebrates (North Atlantic) – sea

scallop. U.S. Fish Wildl. Serv. Biol. Rep. 82(11.67).

13 p.

Murawski, S. and S. Wigley. 1995. Sea scallop. In

Conservation and Utilization Division, Northeast

Fisheries Science Center eds. Status of the fishery

resources of the northeastern United States for 1994.

p. 123-125. NOAA Tech. Mem. NMFS-NE-108.

Naidu, K.S. 1970. Reproduction and breeding cycle of the

giant scallop Placopecten magellanicus (Gmelin) in

Port au Port Bay, Newfoundland. Can. J. Zool. 48:

1003-1012.

Naidu, K.S. 1991. Sea scallop, Placopecten

Magellanicus. In S.E. Shumway ed. Scallops:

biology, ecology and aquaculture. p. 861-897.

Developments in Aquaculture and Fisheries Sciences

21. Elsevier Science Publishing, B.V., Amsterdam.

Naidu, K.S. and J.T. Anderson. 1984. Aspects of scallop

recruitment on St. Pierre Bank in relation to

oceanography and implications for resource

management. Can. Atl. Fish. Sci. Adv. Comm. Res.

Doc. 84/29. 9 p.

Naidu, K.S. and S.A. Meron. 1986. Predation of scallops

by American plaice and yellowtail flounder. Can. Atl.

Fish. Sci. Adv. Comm. Res. Doc. 86/62. 9 p.

Naidu, K.S. and R. Scalpen. 1979. Settlement and survival

of giant scallop, Placopecten magellanicus, larvae on

enclosed polyethylene film collectors. In T.V.R.

Pillay and Wm. A. Dill eds. Advances in aquaculture.

p. 379-381. Papers presented at FAO Technical

Conference on Aquaculture, Kyoto, Japan, May 26-

June 2, 1976. Fishing News Books, Ltd. England.

National Marine Fisheries Service. 1997. Report to

Congress. Status of fisheries of the United States:

Report on the status of fisheries of the United States.

September 1997. [Homepage of the National Marine

Fisheries Service]. [Online]. Available: http://www.

nmfs.gov/sfa/Fstatus.html.

[NEFMC] New England Fishery Management Council.

1993. Amendment #4 and supplemental environmental impact statement to the sea scallop Fishery

Management Plan. Vol. 1. July 1993. NEFMC.

[Saugus, MA.] 296 p.

Nelson, G.A. and M.R. Ross. 1992. Distribution, growth

and food habits of the Atlantic wolffish (Anarhichas

lupus) from the Gulf of Maine-Georges Bank region.

J. Northwest Atl. Fish. Sci. 13: 53-61.

Northeast Fisheries Science Center. 1997. Report of the

23rd Northeast Regional Stock Assessment

Workshop (23rd SAW): Stock Assessment Review

Committee (SARC) consensus summary of

assessments. Northeast Fish. Sci. Cent. Ref. Doc. 97-

05. 191 p.

Parsons, G.J., M.J. Dadswell, and J.C. Roff. 1993.

Influence of biofilm on settlement of sea scallop,

Placopecten magellanicus (Gmelin, 1791), in

Passamaquoddy Bay, New Brunswick, Canada. J.

Shellfish Res. 12: 279-283.

Parsons, G.J., S.M.C. Robinson, R.A. Chandler, L.A.

Davidson, M. Lanteigne, and M.J. Dadswell. 1992a.

Intra-annual and long-term patterns in the reproductive cycle of giant scallops Placopecten magellanicus

(Bivalvia: Pectinidae) from Passamaquoddy Bay,

New Brunswick, Canada. Mar. Ecol. Prog. Ser. 80:

203-214.

Parsons, G.J., C.R. Warren-Perry, and M.J. Dadswell.

1992b. Movements of juvenile sea scallops

Placopecten magellanicus (Gmelin, 1791) in

Passamaquoddy Bay, New Brunswick. J. Shellfish

Res. 11: 295-297.

Patwary, M.U., E.L. Kenchington, C.J. Bird, and E.

Zouros. 1994. The use of random amplified polymorphic DNA markers in genetic studies of the sea

scallop Placopecten magellanicus (Gmelin 1791). J.

Shellfish Res. 13: 547-553.

Pearce, C.M, S.M. Gallager, J.L. Manuel, D.A. Manning,

R.K. O’Dor, and E. Bourget. 1998. Effect of

thermoclines and turbulence on depth of larval

settlement and spat recruitment of the giant scallop

Placopecten magellanicus in 9.5 m deep laboratory

mesocosms. Mar. Ecol. Prog. Ser. 165: 195-215.

Posgay, J.A. 1950. Investigations of the sea scallop,

Pecten grandis. In Third report on investigations of

the shellfisheries of Massachusetts. Commw. Mass.

Dep. Conserv. Div. Mar. Fish. p. 24-30.

Posgay, J.A. 1953. Sea scallop investigations. In Sixth

report on investigations of methods of shellfisheries

of Massachusetts. Commw. Mass. Dep. Conserv. Div.

Mar. Fish. p. 9-25.

Posgay, J.A. 1976. Population assessment of the Georges

Bank sea scallop stocks. ICES C.M. 1976/34. 8 p.

Posgay, J.A. 1981. Movement of tagged sea scallops on

Georges Bank. Mar. Fish. Rev. 43(4): 19-25.

Posgay, J.A. 1982. Sea scallop Placopecten magellanicus.

In M.D. Grosslein and T.R. Azarovitz eds. Fish

distribution. p. 130-133. MESA New York Bight

Atlas Monograph 15. N.Y. Sea Grant Institute,

Albany, NY.

Posgay, J.A. and K.D. Norman. 1958. An observation on

the spawning of the sea scallop, Placopecten

magellanicus (Gmelin), on Georges Bank. Limnol.
Page 10

Oceanogr. 3: 478.

Potter, T.M., B.A. MacDonald, and J.E. Ward. 1997.

Exfoliation of epithelial cells by the scallop

Placopecten magellanicus: seasonal variation and the

effects of elevated water temperatures. Mar. Biol.

127: 463-472.

Reid, R., F. Almeida, and C. Zetlin. 1999. Essential fish

habitat source document: Fishery independent

surveys, data sources, and methods. NOAA Tech.

Mem. NMFS-NE-122. 39 p.

Robert, G., M.A.E. Butler-Connolly, and M.J. Lundy.

1986. Bay of Fundy scallop stock assessment, 1985.

Can. Atl. Fish. Sci. Adv. Comm. Res. Doc. 86/40. 25

p.

Robinson, S.M.C., J.D. Martin, R.A. Chandler, and D.

Bishop. 1996. A possible option for enhancement of

the wild fishery for the sea scallop, Placopecten

magellanicus. J. Shellfish Res. 15 (Abstract): 483.

Robinson, W.E., W.E. Wehling, M.P. Morse, and G.C.

McLeod. 1981. Seasonal changes in soft-body

component indices and energy reserves in the Atlantic

deep-sea scallop, Placopecten magellanicus. Fish.

Bull. (U.S.) 79: 449-458.

Schick, D.F. 1979. Scallop population dynamics, scallop

project 3-267-R. Completion report. Sept. 1976-May

1979. Maine Dep. Mar. Res.

Schmitzer, A.C., W.D. DuPaul, and J.E. Kirkley. 1991.

Gametogenic cycle of sea scallops (Placopecten

magellanicus (Gmelin, 1791) in the mid-Atlantic

Bight. J. Shellfish Res. 10: 221-228.

Serchuk, F.M. and R.S. Rak. 1983. Biological

characteristics of offshore Gulf of Maine sea scallop

populations: size distributions, shell height-meat

weight relationships and relative fecundity patterns.

U.S. Natl. Mar. Fish. Serv. Northeast Fish. Cent.,

Woods Hole Lab. Ref. Doc. 83-07. 42 p.

Serchuk, F.M. and S.E. Wigley. 1984. Results of the 1984

USA sea scallop research vessel survey: status of sea

scallop resources in the Georges Bank, Mid-Atlantic

and Gulf of Maine regions and abundance and

distribution of Iceland scallops off the southeastern

coast of Cape Cod. U.S. Natl. Mar. Fish. Serv.

Northeast Fish. Cent. Woods Hole Lab. Ref. Doc. 83-

84. 74 p.

Serchuk, F.M., P.W. Wood, J.A. Posgay, and B.E. Brown.

1979. Assessment and status of sea scallop

(Placopecten magellanicus) populations off the

northeast coast of the United States. Proc. Nat.

Shellfish. Assoc. 69: 161-191.

Serchuk, F.M., P.W. Wood, Jr. and R.S. Rak. 1982.

Review and assessment of the Georges Bank, MidAtlantic and Gulf of Maine Atlantic sea scallop

(Placopecten magellanicus) resources. U.S. Natl.

Mar. Fish. Serv. Northeast Fish. Cent. Woods Hole

Lab. Ref. Doc. 82-06. 132 p.

Shumway, S.E., J. Barter, and J. Stahlnecker. 1988.

Seasonal changes in oxygen consumption of the giant

scallop, Placopecten magellanicus (Gmelin). J.

Shellfish Res. 7: 77-82.

Shumway, S.E., D. Packer, and L.M. Cargnelli. In

preparation. Synopsis of biological data on sea

scallops, Placopecten magellanicus. U.S. Natl. Mar.

Fish. Serv., Northeast Fish Sci. Cent., James J.

Howard Mar. Sci. Lab., Highlands, NJ.

Shumway, S.E., R. Selvin, and D.F. Schick. 1987. Food

resources related to habitat in the scallop Placopecten

magellanicus (Gmelin, 1791): a qualitative study. J.

Shellfish Res. 6: 89-95.

Squires, H.J. 1962. Giant scallops in Newfoundland

coastal waters. Bull. Fish. Res. Board Can. 135. 29 p.

Stevenson, J.A. 1936. The Canadian scallop: its fishery,

life history, and some environmental relationships.

M.A. thesis, Univer. of Western Ontario, London,

Ontario. 164 p.

Stewart, P.L. and S.H. Arnold. 1994. Environmental

requirements of the sea scallop (Placopecten

magellanicus) in eastern Canada and its response to

human impacts. Can. Tech. Rep. Fish. Aquat. Sci.

2005: 1-36.

Thouzeau, G., G. Robert, and S.J. Smith. 1991a. Spatial

variability in distribution and growth of juvenile and

adult sea scallops Placopecten magellanicus

(Gmelin) on eastern Georges Bank (northwest

Atlantic). Mar. Ecol. Prog. Ser. 74: 205-218.

Thouzeau, G., G. Robert, and R. Ugarte. 1991b. Faunal

assemblages of benthic megainvertebrates inhabiting

sea scallop grounds from eastern Georges Bank, in

relation to environmental factors. Mar. Ecol. Prog.

Ser. 74: 61-82.

Tremblay, M.J., J.W. Loder, F.E. Werner, C.E. Naimie,

F.H. Page, and M.M. Sinclair. 1994. Drift of sea

scallop larvae Placopecten magellanicus on Georges

Bank: A model study of the roles of mean advection,

larval behavior and larval origin. Deep-Sea Res. II.

Top. Stud. Oceanogr. 41: 7-49.

Tremblay, M.J., L.D. Meade, and G.V. Hurley. 1987.

Identification of planktonic sea scallop larvae

(Placopecten magellanicus) (Gmelin). Can. J. Fish.

Aquat. Sci. 44: 1361-1366.

Tremblay, M.J. and M.M. Sinclair. 1986. The horizontal

distribution of larval sea scallops (Placopecten

magellanicus) in the Bay of Fundy, on the Scotian

Shelf and on Georges Bank. Northwest Atl. Fish.

Organ. (NAFO) Sci. Counc. Res. Doc. 86/98. 15 p.

Tremblay, M.J. and M.M. Sinclair. 1988. The vertical and

horizontal distribution of sea scallop (Placopecten

magellanicus) larvae in the Bay of Fundy in 1984 and

1985. J. Northwest Atl. Fish. Sci. 8: 43-53.

Tremblay, M.J. and M. Sinclair. 1990a. Diel vertical

migration of sea scallop larvae Placopecten

magellanicus in a shallow embayment. Mar. Ecol.

Prog. Ser. 67: 19-25.

Tremblay, M.J. and M. Sinclair. 1990b. Sea scallop larvae

Placopecten magellanicus on Georges Bank: vertical
Page 11

distribution in relation to water column stratification

and food. Mar. Ecol. Prog. Ser. 61: 1-15.

Tremblay, M.J. and M. Sinclair. 1992. Planktonic sea

scallop larvae (Placopecten magellanicus) in the

Georges Bank region: broadscale distribution in

relation to physical oceanography. Can. J. Fish.

Aquat. Sci. 49: 1597-1615.

Welch, W.R. 1950. Growth and spawning characteristics

of the sea scallop, Placopecten magellanicus

(Gmelin) in Maine waters. M.S. Thesis, Univer. of

Maine, Orono, ME. 95 p.

Wildish, D.J. and A.M. Saulnier. 1992. The effect of

velocity and flow direction on the growth of juvenile

and adult giant scallops. J. Exp. Mar. Biol. Ecol. 155:

133-143.

Worms, J.M. and L.A. Davidson. 1986. Some cases of

hermaphroditism in the sea scallop Placopecten

magellanicus (Gmelin) from the southern Gulf of St.

Lawrence, Canada. Venus Jpn. J. Malacol. 45: 116-

126.

Zouros, E. and K. Gartner-Kepay. 1985. Influence of

environment and human selection on the genetic

structure of some economically important marine

animal species. Final rep., Canadian Dep. of Supply

and Services Contract: File No. 08SC.FP101-3-0301.
Page 12

Table 1. Summary of life history and habitat parameters for sea scallop, Placopecten magellanicus. Abbreviations: BOF

= Bay of Fundy, GB = Georges Bank, MAB = Mid-Atlantic Bight, NB = New Brunswick, NF = Newfoundland, NH =

New Hampshire, NJ = New Jersey, PB = Passamaquoddy Bay, SS = Scotian Shelf.

Life Stage Size and Growth Habitat Substrate

Eggs 1 Average diameter of spawned eggs:

66.8+1.6 μm.

Average wet weight of spawned eggs:

1.6 x 10-7 g.

Fertilized eggs are slightly heavier than

seawater and probably remain on the sea floor

as they develop into the first free-swimming

larval stages.

Larvae 2 Larval length < 1 mm.

Larvae grow through 4 larval stages in 4-6

weeks (on GB), then settle to the bottom

(assumed to occur by mid-December);

maximum larval settlement in PB occurs in

late September.

Development times: 4 days to straight

hinge veliger at 12-18o

C; 28 days to

pediveliger at 15oC, 40 days at 12-16oC; 35

days to settlement. Pediveligers delayed

metamorphosis until suitable substrates

were found.

Growth rates: 3.1-3.5 μm/day (Trinity Bay,

NF), 4.3-4.8 μm/d (PB and GB).

Fall density on GB ranged 120-1500/m2

.

Vertical distribution: in mixed areas, larvae

distributed evenly through water column; in

stratified areas, larvae aggregated above

pycnocline.

Vertical migration: in response to solar cues;

shallower during night than day (in Grand

Manan, NB, larvae concentrated in upper 10

m of water column; high concentration in

upper 5 m only at night).

Able to penetrate the thermocline at ~200 μm

length.

PB veligers generally found shallower than GB

veligers.

Larvae settle in areas of gravelly sand with

shell fragments; select substrates covered

with a biofilm.

In laboratory studies, larvae settle on

undersides of pebbles, shell and glass

fragments. Artificial substrates have been

successful as settlement substrate.

Juveniles 3 Size ~1-80 mm shell height.

Average shell height at age: 1 - 14.4 mm, 2

- 44.5 mm (50.8 at 66-70 m deep, 33.8 mm

at 81-85 m).

Average shell height decreases with

increasing depth.

Growth of BOF scallops peaks in July and

is best predicted by temperature.

Growth rate in one study: 0.047-0.199

mm/day shell height.

Maximum density of 1 and 2 year old scallops

(0.88-1.65 juveniles/m2

) found on NE Georges

Bank at depths of 62-91 m; age 1 were less

dispersed than age 2 and mainly located on a

gravel-pebble deposit in the northern half of

the Bank.

In a PB study, 76% of the scallops moved an

average of 3.3 m in 4 months.

Mainly found on gravel, small rocks, shells

and silt, which permit attachment of

juveniles. The preferred substrates are

associated with low concentrations of

inorganics (optimal for feeding).

Adults 4 Size: approximately > 80 mm, up to 170

mm shell height.

Average shell height at age on GB: 3 - 72.0

mm, 4 - 89.5 mm, 5 – 101.7 mm, 6 - 112.0

mm, 7 - 121.0 mm.

Growth rates of BOF scallops in lab: 0.020-

0.121 mm/d shell height.

Wide distribution on offshore banks and

coastal waters from NF to Cape Hatteras; from

low tide level to ~100 m line; generally

shallower in northern populations.

On GB, 4 spatially separated sub-populations

(Northern Edge & NE Peak, SE Part, Great

South Channel east, Great South Channel

west) are linked by larval transport; largest

concentrations on N Edge and NE Peak at 37-

100 m, intermediate in central area, at 70-110

m and low to the south.

In Maine, more abundant on Fippenies Ledge

(0.3±0.7 - 1.0±2.2 /m2) than on Jeffreys Ledge

(0.2±0.5/m2); depths ranged from 56-84m.

In MAB, largest concentrations south of Long

Island and off coast of NJ; collected at depths

of 31-80 m (average 55 m).

Generally found in seabed areas with

coarse substrate, usually gravel, shells and

rock. Typically abundant in areas with low

levels of inorganic suspended particulates

(fine clay size particles).

Spawning

Adults 5

Some scallops mature as early as 30 mm,

but most mature at 90 mm (in PB).

Scallops 50-90 mm (shell height) spawn

first, followed by those > 90 mm (on GB).

Reproductive effort increases with age and

size.

Spawning scallops are found at a variety of

depths ranging from 13-180 m: Georges Bank,

60-68 m (egg production is highest on N Edge

and NE Peak); Damariscotta River, shallowwater study site, 13-20 m; Gulf of Maine,

deep-water study site, 170-180 m; MidAtlantic Bight (Long Island to Hatteras), 37-

64 m.

Spawning more common on gravel than

any other sediment type.

1

 Langton et al. (1987) 2

 Culliney (1974), Beninger (1987), Langton and Robinson (1990), Tremblay and Sinclair (1990a, b; 1992), Thouzeau et al. (1991a), McGarvey et al. (1992), Parsons et al.

 (1993), Gallager et al. (1996), Manuel et al. (1996a, b; 1997), Robinson et al. (1996) 3

 Thouzeau et al. (1991a), Parsons et al. (1992b), Wildish and Saulnier (1992), Stewart and Arnold (1994), Kleinman et al. (1996) 4

 Mackenzie et al. (1978), Langton and Robinson (1990), Thouzeau et al. (1991a), McGarvey et al. (1992, 1993), Wildish and Saulnier (1992), Stewart and Arnold (1994) 5

 Posgay and Norman (1958), Mackenzie et al. (1978), Barber et al. (1988), MacDonald and Thompson (1988), Kirkley and Dupaul (1991), Schmitzer et al. (1991),

 McGarvey et al. (1992), Parsons et al. (1992a)
Page 13

Table 1. cont’d.

Life Stage Temperature Salinity Currents Prey

Eggs 1 Eggs maintained in the laboratory

at 13-17oC hatched 32 days post

fertilization.

Larvae 2 Laboratory reared larvae from NH

were viable at 12-18oC; mass

mortalities when reared at 19o

C.

Duration of larval stages shorter at

higher temperatures.

One study shows that larval

abundance on GB peaks when

thermal stratification is high.

Laboratory reared

larvae from NH viable

at salinities as low as

10.5 ppt (at 15oC for

42 h), although

behavior was abnormal

(lack of swimming).

Swimming and other

behaviors appeared

normal within 16.9-30

ppt.

Larvae circulate with residual currents

ranging from 6-25 cm/s.

In BOF there is some transport of larvae

via residual currents, but most larvae

remain near area of major spawning.

Larval exchange influenced by duration

and depth of planktonic drift, gyre

strength and weak cross-isobath flow.

Differences in vertical distribution may

be related to differences in horizontal

transport by currents.

Filter feeders, primarily on

phytoplankton, diatoms and

microscopic animals; also

dissolved organic matter,

detrital particles and bacteria.

Juveniles 3 Juveniles successfully maintained

at temperatures of 1.2-15oC in

laboratory. High exfoliation of

epithelial cells at 21o

C; damage to

gills, mantles, and gonads at

exposure to 14.7o

C followed by

21o

C.

Consumption rate by predators,

rate of scallop movement, and

growth rate increases with

temperature.

Optimum velocity for growth is 10 cm/s;

> 10 cm/s can result in reduced feeding

rate; but this can be avoided in areas

with strong currents by feeding during

periods of slack water (high & low tide).

Juveniles from GB drift with currents to

the south as they grow older.

Byssal attachment by scallops < 12 mm

shell height may be an adaptation to

strong currents.

Opportunistic feeders on

suspended particles, primarily

phytoplankton.

Adults 4 Optimal growth at 10-15o

C; lethal

temperature: > 21o

C.

Optimal survival at

salinities approaching

full-strength seawater;

lower lethal threshold:

16.5 ppt.

Water movement critical for dispersal,

replenishment of suspended food

particles, supply of oxygen and removal

of waste products.

Adults drift with tidal currents (on GB,

39% moved toward the SE, 30% to the

NW). A 1989 study showed southward

drift of adults.

Strong tidal currents (> 10 cm/s) inhibit

feeding; fluctuations in scallop clearance

rates are directly related to flow velocity;

clearance rates significantly lower at low

(< 4 cm/s) and high (> 9 cm/s) flow

speeds.

Filter feeders on phytoplankton

and other suspended organic

particulates from the water; gut

contents reflect available

organisms in the immediate

environment.

Stomach contents of scallops

(90-140 mm shell height) from

shallow and deep study sites in

Maine: 27 species of algae

ranging in size from 10-350 μm,

pollen grains, ciliates,

zooplankton tests, detrital

material and bacteria.

Spawning

Adults 5

Spawning in nature occurs at

temperatures ranging from 6.5-

16o

C. GB: typically 9-11.2oC. Isle

of Shoals, NH: 14-16o

C; spawning

triggered in lab when temperature

was raised abruptly from 5 to

10o

C, or from 12 to 15oC.

MAB: spawning coincided with

decreasing and stable

temperatures in winter/spring and

increasing temperatures in fall;

6.5o

C off Long Island; 11oC off

Chincoteague, VA. Spawning may

be delayed by low summer

temperatures.

Tidally related spawning cue in PB;

spawning occurs just prior to spring

tides.

1

 Karney (1996)

2

 Culliney (1974), Tremblay and Sinclair (1986, 1990a, b; 1992), Thouzeau et al. (1991a), Tremblay et al. (1994), Manuel et al. (1996a, 1997) 3

 Shumway et al. (1987), Manuel and Dadswell (1991), Thouzeau et al. (1991a), Wildish and Saulnier (1992), Manuel and Dadswell (1993), Barbeau and Scheibling (1994b),

 Stewart and Arnold (1994), Kleinman et al. (1996), Potter et al. (1997) 4

 Posgay (1981), Shumway et al. (1987), Thouzeau et al. (1991a), Wildish and Saulnier (1992), Stewart and Arnold (1994), Cranford et al. (1998) 5

 Culliney (1974), MacKenzie et al. (1978), Schmitzer et al. (1991), Parsons et al. (1992a)
Page 14

Table 1. cont’d.

Life Stage Predators Spawning Notes

Eggs 1 Predation by a variety of bottom

predators.

see spawning adults Fecundity ranges from 1-270 million eggs/

individual. Egg production is positively

correlated with age and shell height

(exponentially).

Larvae 2 Scallop larvae potentially

preyed on by filter feeders and

larval and adult planktivores.

Early larval stages (trocophore and veliger)

are pelagic, swim freely.

PB larvae reach the veliger stage faster than

larvae on GB; a shortened trocophore stage

may allow earlier vertical migration and

control of horizontal movement (strong tides

in this area make larvae vulnerable to being

washed away).

No large scale exchange between GB and the

SS; self-seeding likely for the Great South

Channel & NE Peak; simulations indicate

significant larval exchange between NE Peak,

Southern Flank and Great South Channel.

Juveniles 3 Potential groundfish predators

include cod, American plaice,

Atlantic wolffish and winter

flounder. Lab studies have

shown that rock crabs, lobsters

and sea stars are also potential

predators (especially of smaller

scallops).

Larger predators had distinct

preference for larger scallops;

but scallops > 70 mm were

rarely preyed upon.

The distribution of juveniles is determined by

the hydrodynamic regime during the larval

stage and by differential post-larval mortality

at settlement.

In laboratory studies, growth rate and

metabolic condition increased with

temperature; swimming frequency did not

affect growth, but increased mass of adductor

muscle. Somatic production (i.e., growth)

increases to age 5 then levels off.

Adults 4 Adults damaged by dredging

and trawling activity have been

shown to be preyed upon by

rock crabs starfish, lobster, and

groundfish (winter flounder and

sculpins).

see spawning adults Sea scallop populations on GB are the largest,

densest and most intensively exploited of the

species.

The Northern Edge (2.91 g/m2) and NE Peak

(1.32 g/m2) have the highest biomass (meat

weight) density (other areas on GB much

lower, 0.29-0.44). By area, the NE Peak has

the highest biomass (20599 mt) followed by

the Northern Edge (4291 mt).

Sex ratios: GB, 1:1; MAB, 1.4:1 (male:

female, 1975 studies).

Spawning

Adults 5

GB: spawning in late Sept-early Oct; reports of a

semi-annual reproductive cycle on northeast GB:

spring spawning in May-June and fall spawning in

Sept-Oct; fall is larger, more synchronized and

consistent among years, spring is more protracted,

erratic.

Maine: in shallow sites, spawning in Sept-Oct; deep

water sites, possible minor spawning in May, more

abrupt spawning in Oct (1 month later than in shallow

sites).

PB: relatively consistent reproductive cycle with major

spawning in late July-late Sept (peaked Aug); similar

to spawning period in southeast NF and areas of

GOM.

NJ: mostly Sept-Nov, some in June-July.

MAB: Semi-annual gametogenic cycle; spring

(May/June) and fall (Nov) spawning; spring spawning

stronger, more predictable than fall (longer duration

and greater fecundity in spring).

GOM: deep-water scallops produced fewer

eggs than shallow-water scallops; lowered

fecundity reduces the probability that the

deep-water population is self-sustaining.

MAB: the significance of the spring

spawning event to recruitment processes

uncertain. In spring, deep water scallops

initiated gamete production about 1 month

later than shallow water scallops.

Reproduction and size attained by individuals

are largely controlled by local environmental

conditions.

Fecundity and production greater, but

longevity reduced in NJ scallops (avg.

longevity 1-10 yrs), than in those from NB

and NF (avg. 1-12 yrs).

1

 Langton et al. (1987), Stewart and Arnold (1994) 2

 Tremblay and Sinclair (1986, 1992), Langton and Robinson (1990), Tremblay et al. (1994), Manuel et al. (1996a) 3

 Elner and Jamieson (1979), Langton et al. (1987), Thouzeau et al. (1991a), Barbeau and Scheibling (1994a, b), Kleinman et al. (1996) 4

 MacKenzie et al. (1978), McGarvey et al. (1992, 1993), Stewart and Arnold (1994) 5

 Posgay and Norman (1958), Culliney (1974), MacKenzie et al. (1978), Beninger (1987), Barber et al. (1988), MacDonald and Thompson (1988), DuPaul et al. (1989),

 Kirkley and DuPaul (1991), Schmitzer et al. (1991), Dadswell and Parsons (1992), McGarvey et al. (1992), DiBacco et al. (1995)
Page 15

Table 2. Relative abundance of egg, larval, juvenile, and adult sea scallops, Placopecten magellanicus, in New England

bays and estuaries by salinity zone, based on Estuarine Living Marine Resources (ELMR) data in Jury et al. (1994).

Eggs Larvae Juveniles Adults

T M S T M S T M S T M S

Passamaquoddy Bay RA RA RA RA

Englishman/Machias Bays A RA RA RA

Narraguagus Bay A RA RA RA

Blue Hill Bay A RA RA RA

Penobscot Bay RA RA RA RA

Muscongus Bay CCCC

Damariscotta River CCCC

Sheepscot River CCCC

Kennebec/Androscoggin Rivers RRRR

Casco Bay CCCC

Saco Bay RRRR

Wells Harbor

Great Bay RCC

Merrimack River

Massachusetts Bay CCCC

Boston Harbor na na R R

Cape Cod Bay AAAA

Salinity zone: T = tidal fresh, M = mixing zone, S = seawater.

Relative abundance: H = highly abundant, A = abundant, C = common, R = rare, blank = not present, na = no data

available.
Page 16

Figure 1. The sea scallop, Placopecten magellanicus (from Mullen and Moring 1986).
Page 17

Figure 2. Generalized life cycle of the sea scallop (from Stewart and Arnold 1994).
Page 18

Figure 3. Map of Georges Bank indicating the five sub-regions and the clockwise flow of the residual current (from

McGarvey et al. 1993).
Page 19

Figure 4. Distribution of sea scallop spawning beds off the northeast coast of North America (from Shumway et al., in

prep.).
Page 20

Figure 5. Distribution of sea scallops collected during NEFSC scallop surveys during summer 1982-1997. Dots

represent stations where scallops were taken [see Reid et al. (1999) for details].
Page 21

Figure 6. Commercial landings and survey indices of sea scallops for the Gulf of Maine, Georges Bank, and MidAtlantic.

Gulf of Maine

1960 1965 1970 1975 1980 1985 1990 1995 2000

Meats (mt x 1000)

0.0

0.5

1.0

1.5

2.0

Georges Bank

Year

1960 1965 1970 1975 1980 1985 1990 1995 2000

Meats (mt x 1000)

0

2

4

6

8

10

Stratified mean catch/tow (kg meats)

0.0

0.5

1.0

1.5

Commercial landings (mt)

Survey index (kg)

Middle Atlantic

Year

1960 1965 1970 1975 1980 1985 1990 1995 2000

Meats (mt x 1000)

0

2

4

6

8

Stratified mean catch/tow (kg meats)

0.0

0.5

1.0

NORTHEAST FISHERIES SCIENCE CENTER

Dr. Michael P. Sissenwine, Science & Research Director

CAPT John T. Moakley, Operations, Management & Information Services Staff Chief

Teri L. Frady, Research Communications Unit Chief

Jon A. Gibson, Biological Sciences Editor & Laura S. Garner, Editorial Assistant

Publishing in NOAA Technical Memorandum NMFS-NE

Manuscript Qualification

This series represents a secondary level of scientific publishing in the National Marine Fisheries Service (NMFS). For

all issues, the series employs thorough internal scientific review,

but not necessarily external scientific review. For most issues,

the series employs rigorous technical and copy editing. Manuscripts that may warrant a primary level of scientific publishing

should be initially submitted to one of NMFSs primary series

(i.e., Fishery Bulletin, NOAA Technical Report NMFS, or Marine Fisheries Review).

Identical, or fundamentally identical, manuscripts should

not be concurrently submitted to this and any other publication

series. Manuscripts which have been rejected by any primary

series strictly because of geographic or temporal limitations may

be submitted to this series.

Manuscripts by Northeast Fisheries Science Center

(NEFSC) authors will be published in this series upon approval

by the NEFSC's Deputy Science & Research Director. Manuscripts by non-NEFSC authors may be published in this series if:

1) the manuscript serves the NEFSCs mission; 2) the manuscript meets the Deputy Science & Research Directors approval; and 3) the author arranges for the printing and binding

funds to be transferred to the NEFSCs Research Communications Unit account from another federal account. For all manuscripts submitted by non-NEFSC authors and published in this

series, the NEFSC will disavow all responsibility for the manuscripts contents; authors must accept such responsibility.

The ethics of scientific research and scientific publishing

are a serious matter. All manuscripts submitted to this series are

expected to adhere -- at a minimum -- to the ethical guidelines

contained in Chapter 1 (Ethical Conduct in Authorship and

Publication) of the CBE Style Manual, fifth edition (Chicago,

IL: Council of Biology Editors). Copies of the manual are

available at virtually all scientific libraries.

Manuscript Preparation

Organization: Manuscripts must have an abstract, table of

contents, and -- if applicable -- lists of tables, figures, and

acronyms. As much as possible, use traditional scientific manuscript organization for sections: Introduction, Study Area,

Methods & Materials, Results, Discussion and/or Conclusions, Acknowledgments, and References Cited.

Style: All NEFSC publication and report series are obligated to conform to the style contained in the most recent edition

of the United States Government Printing Office Style Manual.

That style manual is silent on many aspects of scientific manuscripts. NEFSC publication and report series rely more on the

CBE Style Manual, fifth edition.

For in-text citations, use the name-date system. A special

effort should be made to ensure that the list of cited works

contains all necessary bibliographic information. For abbreviating serial titles in such lists, use the most recent edition of the

Serial Sources for the BIOSIS Previews Database (Philadelphia,

PA: Biosciences Information Service). Personal communications must include date of contact and full name and mailing

address of source.

For spelling of scientific and common names of fishes,

mollusks, and decapod crustaceans from the United States and

Canada, use Special Publications No. 20 (fishes), 26 (mollusks),

and 17 (decapod crustaceans) of the American Fisheries Society

(Bethesda, MD). For spelling of scientific and common names

of marine mammals, use Special Publication No. 4 of the

Society for Marine Mammalogy (Lawrence, KS). For spelling in

general, use the most recent edition of Websters Third New

International Dictionary of the English Language Unabridged

(Springfield, MA: G.&C. Merriam).

Typing text, tables, and figure captions: Text, including

tables and figure captions, must be converted to, or able to be

coverted to, WordPerfect. In general, keep text simple (e.g.,

dont switch fonts, dont use hard returns within paragraphs,

dont indent except to begin paragraphs). Especially, dont use

WordPerfect graphics for embedding tables and figures in text.

If the automatic footnoting function is used, also save a list of

footnotes as a separate WordPerfect file. When the final draft is

ready for review, save the text, tables, figure captions, footnotes,

and front matter as separate document files.

Tables should be prepared using all tabs or all spaces

between columnar data, but not a combination of the two.

Figures must be original (even if oversized) and on paper; they

cannot be photocopies (e.g., Xerox) unless that is all that is

available, nor be on disk. Except under extraordinary circumstances, color will not be used in illustrations.

Manuscript Submission

Authors must submit one paper copy of the double-spaced

manuscript, one magnetic copy on a disk, and original figures (if

applicable). NEFSC authors must include a completely signedoff NEFSC Manuscript/Abstract/Webpage Review Form.

Non-NEFSC authors who are not federal employees will be

required to sign a Release of Copyright form.

Send all materials and address all correspondence to:

Jon A. Gibson, Biological Sciences Editor

Northeast Fisheries Science Center

National Marine Fisheries Service

166 Water Street

Woods Hole, MA 02543-1026 USA
Research Communications Unit

Northeast Fisheries Science Center

National Marine Fisheries Service, NOAA

166 Water St.

Woods Hole, MA 02543-1026

NOAA Technical Memorandum NMFS-NE -- This series is issued irregularly. The series includes: data reports of longterm or large area studies; synthesis reports for major resources or habitats; annual reports of assessment or monitoring programs;

documentary reports of oceanographic conditions or phenomena; manuals describing field and lab techniques; literature surveys of major

resource or habitat topics; findings of task forces or working groups; summary reports of scientific or technical workshops; and indexed

and/or annotated bibliographies. All issues receive internal scientific review and most issues receive technical and copy editing. Limited

free copies are available from authors or the NEFSC. Issues are also available from the National Technical Information Service, 5285

Port Royal Rd., Springfield, VA 22161.

Fishermen's Report and The Shark Tagger -- The Fishermen's Report (FR) is a quick-turnaround report on the

distribution and relative abundance of commercial fisheries resources as derived from each of the NEFSC's periodic research vessel

surveys of the Northeast's continental shelf. There is no scientific review, nor any technical or copy editing, of the FR; copies are available

through free subscription. The Shark Tagger (TST) is an annual summary of tagging and recapture data on large pelagic sharks as derived

from the NMFS's Cooperative Shark Tagging Program; it also presents information on the biology (movement, growth, reproduction, etc.)

of these sharks as subsequently derived from the tagging and recapture data. There is internal scientific review, but no technical or copy

editing, of the TST; copies are available only to participants in the tagging program.

Northeast Fisheries Science Center Reference Document -- This series is issued irregularly. The series

includes: data reports on field and lab observations or experiments; progress reports on continuing experiments, monitoring, and

assessments; background papers for scientific or technical workshops; and simple bibliographies. Issues receive internal scientific review

but no technical or copy editing. No subscriptions. Free distribution of single copies.

The mission of NOAA's National Marine Fisheries Service (NMFS) is "stewardship of living marine resources for the

benefit of the nation through their science-based conservation and management and promotion of the health of their

environment." As the research arm of the NMFS's Northeast Region, the Northeast Fisheries Science Center (NEFSC)

supports the NMFS mission by "planning, developing, and managing multidisciplinary programs of basic and applied

research to: 1) better understand the living marine resources (including marine mammals) of the Northwest Atlantic, and

the environmental quality essential for their existence and continued productivity; and 2) describe and provide to

management, industry, and the public, options for the utilization and conservation of living marine resources and

maintenance of environmental quality which are consistent with national and regional goals and needs, and with

international commitments." Results of NEFSC research are largely reported in primary scientific media (e.g.,

anonymously-peer-reviewed scientific journals). However, to assist itself in providing data, information, and advice to

its constituents, the NEFSC occasionally releases its results in its own media. Those media are in three categories:

Publications and Reports

of the

Northeast Fisheries Science Center

To obtain a copy of a technical memorandum or a reference document, or to subscribe to the fishermen's report,

write: Research Communications Unit, Northeast Fisheries Science Center, 166 Water St., Woods Hole, MA

02543-1026. An annual list of NEFSC publications and reports is available upon request at the above address.

Any use of trade names in any NEFSC publication or report does not imply endorsement.

STANDARD

 MAIL A