NOAA Technical Report NMFS 122

The Summer Flounder, Scup,

and Black Sea Bass Fishery of

the Middle Atlantic Bight and

Southern New England Waters

Gary R. Shepherd

Mark Terceiro

u.S. Department of Commerce

August 1994
U.S. DepartJ:nent

of Conunerce

Ronald H. Brown

Secretary

National Oceanic and

Atmospheric AdnUnistration

D. James Baker

Under Secretary for Oceans and

Atmosphere

National Marine

Fisheries Service

Rolland A. Schmitten

Assistant Administrator for

Fisheries

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NOAA Technical Report NMFS 122

A Technical Report of the Fishery Bulletin

The Summer Flounder, Scup,

and Black Sea Bass Fishery of

the Middle Atlantic Bight and

Southern New England Waters

Gary R. Shepherd

Mark Terceiro

August 1994

u.s. Department of Commerce

Seattle, Washington

The Summer Flounder, Scup, and Black Sea Bass

Fishery of the Middle Atlantic Bight

and Southern New England Waters

GARY R. SHEPHERD and MARK TERCEIRO

Woods Hole Laboratory

Northeast Fisheries Science Center

National Marine Fisheries Seroice

Woods Hole, MA 02543

ABSTRACT

Summer flounder, Paralichthys dentatus, scup, Stenotomus chrysops, and black sea bass,

Centropristis striata, cooccur within the Middle Atlantic Bight and offsouthern New England

and are important components of commercial and recreational fisheries. The commercial

otter trawl fishery for these species is primarily a winter fishery, whereas the recreational

fishery takes place between late spring and autumn. The otter trawl fishery generally targets

summer flounder, and less frequently scup, while black sea bass occurs as bycatch. Trips in

which all three species were present yielded highest aggregate landings per unit of effort

(LPUE) levels and occurred more often than trips landing only one or two species. More

than 50% of the trips in the trawl fishery landed at least two ofthe three species. In contrast,

greater than 75% of the recreational landings of each species occurred as a result of trips

landing only one species. Differences in the fisheries resulted from the interactions of

seasonal changes in species distributions and gear selectivity.

Introduction

Fisheries managers have become increasingly aware of

the need to manage fisheries as mixed species assemblages rather than as single species stocks (Brown et aI.,

1976; Dickie and Kerr, 1982; Kerr and Ryder, 1989).

Multispecies fisheries may be examined from the perspective of biological interactions or technological interactions, defined as the relationship between a mixed

species resource and fishing gear (Pope, 1979). A fishery may be directed toward one species, but any fish

caught that has some economic value is likely to be

landed. Consequently, management strategies must consider technological interactions to provide effective conservation measures.

Within the Middle Atlantic Bight and southern New

England waters (Fig. 1), summer flounder, Paralichthys

dentatus, scup, Stenotomus chrysops, and black sea bass,

Centropristis striata, support important commercial and

recreational fisheries (U.S. Department of Commerce,

1991a). The commercial fishery in the Middle Atlantic

Bight and southern New England involves several gear

types. For each of the three species, the otter trawl

produces >60% of total landings. Significant landings

of scup are also made by pound nets and floating trap

nets (U.S. Department of Commerce, 1991a; Mayol),

while fish traps are effective for both black sea bass and

scup Oune and Reinljes, 1957; Frame and Pearce, 1973;

Eklund and Targett, 1991). The inshore fish trap fishery, which occurs between late spring and late autumn,

is most species-specific, because greater than 96% of

the total catch consists of black sea bass Oune and

Reinljes, 1957; Eklund and Targett, 1991).

Commercial U.S. landings ofsummer flounder, scup,

and black sea bass have fluctuated widely over the past

forty years (U.S. Department ofCommerce, 1991a; Fig.

2). Landings of scup changed most dramatically, consistently ranging from 15,000 to 20,000 metric tons (t)

between 1950 and 1965 but decreasing to an average of

1 Mayo, R. K. 1982. An assessment of the scup, Stenotomus chrysops

(L.), population in the southern New England and Mid-Atlantic

regions. Northeast Fisheries Center, National Marine Fisheries

Service, NOAA, Woods Hole, MA. Woods Hole Lab. Ref. Doc.

82-46,59 p.
2 NOAA Technical Report NMFS 122

SOUTHERN NEW ENGLAND

68

GEORGES

BANK

~\ ... " - .I

o

..,

.'

:t

"!';

t., ~.

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, ' • - , - - - - _ 200 ,M

4 72

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o " F ,',' ~".- ~,,',

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40

42

Figure I

Geographic features of the Middle Atlantic Bight and southern New England area.

5,000 t in the early 1970's (Mayol). Although landings

increased during the late 1970's and early 1980's to

8,000-10,000 t, they have since steadily declined to

4,200 tin 1990 (U.S. Department ofCommerce, 1991a).

Landings of black sea bass have fluctuated between

1,000 and 2,000 t since the mid 1960's (1,500 t in 1990),

although landings were as high as 9,900 tin 1952 (Kenda1l2). Landings of summer flounder were generally

stable between 7,000 and 10,000 t from 1950 to 1962

but declined to 3,000 t by 1969 (U.S. Department of

Commerce, 1991a). Although highly variable from year

to year, landings increased until 1988. Summer flounder landings have declined to about 6,000 t since 1988

(U.S. Department of Commerce, 1991a).

Estimates of recreational landings for all three species have varied considerably over the last twelve years

(Fig. 3). Summer flounder landings declined dramatically from a peak of 16,000 t in 1983 to a record low

2 Kendall, A. W., Jr. 1977. Biological and fisheries data on black

sea bass, Centropristis striata (Linnaeus). Northeast Fisheries Center, National Marine Fisheries Service, NOAA, Sandy Hook Lab.,

Highlands, NJ. Tech. Sers. Rpt. 7., 29 p.
Shepherd and Terceiro: Summer Flounder, Scup, and Black Sea Bass Fishery 3

25 ----,------------------------,

SUMMER

FLOUNDER

\

\

\

\

\ --\ /\

., \

BLACK SE~ ......,-"",'"

BASS

5

10

20

I-

(j) 15

(:)

o

o

-

Figure 2

Annual commercial landings (thousands of t) ofsummer flounder, Paralichthys dentatus, scup, Stenotomus chrysff/Js,

and black sea bass, Centropristis striata, 1950-1990.

YEAR

0--+-.,....-,---,-,--,----,---,-r-.,....,.---,---,,---,-,---,-r-.,....,.---,----,---,--...,.--,----,-r-r-,----,---,--...,.--,----,-,--,----,---,-r-,---,----1

1950 1955 1960 1965 1970 1975 1980 1985 1990

level of 1,600 t in 1989 (U.S. Department of Commerce, 1991a). Black sea bass landings were 8,100 t in

1982 and 6,300 t in 1986 but have otherwise been

consistently around 1,000 to 2,000 t annually (U.S.

Department of Commerce, 1991a). Scup landings varied between 2,000 and 4,000 t annually with the exception of 1986 when landings reached 5,500 t (U.S. Department of Commerce, 1991a).

Fluctuations in recreational landings may partially

reflect changes in fishing effort. Total trips that targeted one of the three species varied from 4.9 million

trips per year in 1986 to 2.8 million trips per year in

1989 (U.S. Department of Commerce, 1991b). The

recreational fishery has been primarily a boat-based

fishery. Approximately 70% of the trips occur on party,

charter, or private boats, with the remaining 30% of trips

from shore (U.S. Department of Commerce, 1991b).

Spatial cooccurrence and feeding habits across two

decades ofstudies suggest that summer flounder, scup,

and black sea bass form a consistent assemblage of

interacting species. Patterns of cooccurrence among

the three species have been previously documented.

Musick and Mercer (1977) examined faunal associations in the Middle Atlantic Bight using fishery-independent otter trawl data and found a statistically significant cooccurrence among summer flounder, scup, and

black sea bass. Gabriel (1989) used cluster analysis to

categorize multispecies assemblages between North

Carolina and Nova Scotia and also identified an association among summer flounder, scup, and black sea bass.

In addition to spatial overlap, diets overlap among

summer flounder, scup, and black sea bass. Smaller

individuals feed primarily on benthic worms, crustaceans, and molluscs, whereas larger individuals may

also consume small fishes (Bigelow and Schroeder, 1953;

Steimle and Ogren, 1982; Mack and Bowman3). This

dietary overlap indicates that these species occupy similar trophic niches. Although the potential for biologi3 Mack, R.C., and R.E. Bowman. 1983. Food and feeding of black

sea bass. Northeast Fisheries Center, National Marine Fisheries

Service, NOAA, Woods Hole, MA. Woods Hole Lab. Ref. Doc.

83-45, 20 p.
4 NOAA Technical Report NMFS 122

20 ---,----------------------------,

15

-en

o

o

010 -....

5

---- -"-

SUMMER

FLOUNDER

/

/\ BLACK

I "SEA BASS I \ ./

I \./

I \

I \

I

I

,,'" ...... .....

1981 1983 1985 1987 1989

0-+-------r--,-------.-----,-------r--,-------.-----,-------r--,--------1

1979

Year

Figure 3

Annual recreational landings (thousands of t) of summer flounder, Paralichthys dentatus, scup, Stenotomus

chrysops, and black sea bass, Centropristis striata, in the Middle Atlantic Bight and southern New England

area, 1979-1990.

cal interactions among the three species has been established, understanding the multispecies nature of

the fisheries is necessary to establish a basis for management. The characteristics of single-species commercial

and recreational fisheries for summer flounder, scup,

and black sea bass have been previously described

(Nesbit and Neville, 1935; June and Rein~es, 1957;

Jensen, 1974; Murawski eta\., 1983), but the multispecies

aspect ofthe fishery has never been examined in detail.

Our objectives were 1) to describe the geographic and

seasonal nature of the commercial otter trawl and recreational hook-and-line fisheries for summer flounder,

scup, and black sea bass in the Middle Atlantic Bight

and southern New England and 2) to characterize the

technological interactions within those fisheries.

Methods

Fishery-independent data were collected during Northeast Fisheries Science Center (NEFSC) biannual bottom trawl surveys conducted between the Gulf ofMaine

and Cape Hatteras, North Carolina. Sampling tows were

conducted in depths from 9 to 366 m at locations

chosen in a stratified random survey design. At each

sampling location, individual fish lengths (total length)

and total weight of the catch were recorded for each

species. Survey history and methodological details were

summarized by Azarovitz (1981) and the U.S. Department ofCommerce (1988). Species distributions based

on survey data were examined for the years 1982 to

1990.

Commercial landings data were collected by trip at

various ports from Maine to Virginia by the NEFSC.

Data on species composition and weight of the landed

catch (kg), effort (days fished), area and depth fished

(m), and vessel characteristics (i.e. gross tonnage and

gear characteristics) were collected from dealer slips

(weighouts) and captain interviews (Burns et aI., 1983).

Interviews also provided information on targeted species that ranged from species-specific targets (i.e. sum-
Shepherd and Terceiro: Summer Flounder, Scup, and Black Sea Bass Fishery 5

mer flounder) to general categories (i.e. flatfish). Only

trips that landed at least one of the three species were

included in the analysis. We confined our analysis to

data collected between 1982 and 1990 because data

were not collected from Maryland and Virginia ports

before 1982. Landings per unit of effort (LPUE) was

calculated for trips as

Geographic distribution of commercial landings were

aggregated to the nearest lO'xl0' square for each quarter of 1987-1989.

Commercial catch data for individual tows were collected by observers on 130 commercial otter trawl trips

during 1989 and 1990. Trips that included an onboard

observer were not interviewed by a port agent and

included in weighout-based LPUE estimates. Species

composition and weight of the discarded portion, tow

location and depth, tow duration, characteristics of the

gear and vessel, and environmental conditions during

the tow were recorded. Tow duration was scaled to a 24-

hour time period to equate a unit of effort on a per tow

basis with total trip effort. Because the entire catch was

sampled rather than the landed catch, catch per unit of

effort (CPUE) of individual tows was calculated as

where

CPUE =fish caught per tow (kg)

tow duration (h/24)

Only tows that were examined by the observer and that

included anyone of the three species were analyzed.

Information on recreational fisheries along the Atlantic coast has been collected annually since 1979 by

the National Marine Fisheries Service as part of the

Marine Recreational Fisheries Statistics Survey (MRFSS)

program. The survey, conducted in bimonthly intervals, estimated catches by species with data collected

during dockside interviews (intercepts) and telephone

surveys (U.S. Department of Commerce, 1991b). Anglers were considered participants in a summer flounder-scup-black sea bass fishery if they caught anyone

of the three species during a trip, similar to the criteria

used for the commercial fisheries. Following the U.S.

where

and

and

LPUE = fish landed per trip (kg)

days fished (dE)

fish landed = fish caught - fish discarded,

d fi h d hours towed per trip ays IS e = .

24

fish caught = fish landed +fish discarded,

d . hours towed per haul

tow uratl0n = .

24

Department of Commerce (1991b), CPUE was calculated from intercept data as

CPUE = number of fish caught

angler trip

where

angler trip = number of anglers per interviewed trip.

Results _

Seasonal Distribution

Data collected during the NEFSC spring and autumn

bottom trawl surveys show a seasonal shift in distribution for all three species from offshore in the spring to

inshore in the autumn (Fig. 4). Scup were distributed

along the 200-m contour between Cape Cod, Massachusetts, and Cape Hatteras, North Carolina, during spring.

Black sea bass occupied the same area but also occurred further inshore, particularly south of Delaware

Bay, while summer flounder were dispersed across the

continental shelf. By early autumn, all three species

were aggregated in coastal waters and their distributions overlapped extensively. All three species may also

be distributed in deeper water (i.e. > 366 m) beyond

the area covered by the bottom trawl survey.

Commercial Fishery

The distribution of the commercial fishery was consistent with species distributions based on fishery-independent survey data. Seasonal distribution of commercial landings for all species are presented in Figure 5.

During winter Uanuary-March), the fishery operated

along the edge ofthe continental shelf, most frequently

south of Nantucket Shoals (Fig. 5). Summer flounder

landings were from areas farther north and east than

those ofscup or black sea bass. An increase in landings

of all species in coastal waters began during the spring

(April-June), particularly toward Long Island and Nantucket Shoals (Fig. 5). Summer flounder landings also

increased from areas further east onto Georges Bank.

By summer Uuly-September), the frequency of trawl

landings for all species declined as the fish were distributed further inshore and presumably into areas less

accessible to large otter trawlers (Fig. 5). Autumn (October-December) was a transitional period when all

three species migrated towards offshore wintering grounds

along the shelf edge; landings for all species were generally distributed across the shelfduring this period (Fig. 5).

Average monthly landings based on commercial

weighout data also reflected the seasonal nature of the
z

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Figure 4

Distribution of summer flounder, Paralichthys dentatus, scup, Stenotomus chrysops, and black sea bass, Centropristis striata, captured in the Northeast Fisheries Science Center spring (A)

and autumn (B) bottom trawl surveys, 1982 1990.
Shepherd and Terceiro: Summer Flounder, Scup, and Black Sea Bass Fishery 7

fisheries (Fig. 6). Landings of trawl-eaught summer

flounder typically peaked between September andJanuary, whereas scup landings peaked between March and

May. Peak black sea bass trawl catches were similar to

scup, occurring between February and April. Landings

by otter trawlers declined during the summer for all

three species. Monthly LPUE by otter trawlers for the

three species followed the same trends.

SUMMER FLOUNDER

x BLACK SEA BASS

c SCUP

APRIL - JUNE

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Figure 5

Seasonal distributions of commercial trawl fishery for summer flounder, Paralichthys dentatus, scup, Stenotomus

chrysops, and black sea bass, Centropristis striata, in the Middle Atlantic Bight and southern New England area,

1987-1989. Catch locations are by species per 10' square.
8 NOAA Technical Report NMFS 122

25

BLACK SEA

,- - 1 - .. /BASS

20 1 \

1 \

W , \

" 1 \

i:! \

Z

w 15 0

a:: SUMMER w

11. SCUP FLOUNDER /

"'" J: 10

IZ

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Oz I

m a: a: > z ..J CJ D.. .... > U

...,

<t w <t D.. <t W U 0 w

LL <t ..., ..., <t en 0 z c

MONTH

Figure 6

Monthly percentage of total annual commercial otter trawl landings of summer flounder, Paralichthys

dentatus, scup, Stenotomus chrysops, and black sea bass, eentTopristis striata, in the Middle Atlantic Bight and

southern New England area, 1982-1990.

Recreational Fishery

The temporal distribution of landings in the recreational fishery was the opposite ofthe commercial trawl

fishery. The recreational fishery peaked during summer and early autumn when the fish were distributed in

estuaries and coastal waters (Fig. 7). Summer flounder

catch consistently peaked during July through August;

scup and black sea bass catches peaked in either May

through June or September through October.

Commercial Interactions

Catch rate and degree of cooccurrence of the three

species in the commercial fishery varied according to

the targeted species, despite overlapping distributions.

The average LPUE for target species based on the

weighout data was 594.9 kg/df for summer flounder,

345.4 kg/dffor scup, and 68.3 kg/dffor black sea bass.

The highest LPUE for summer flounder was obtained

on trips designating summer flounder as the targeted

species (1193.5 kg/df). Scup LPUE was highest in trips

targeting groundfish (1346.9 kg/df), although catch

rates were above average in trips targeting squid (356.1

kg/df) and pelagics (939.8 kg/df). Highest catch rates

(LPUE) of black sea bass were in trips that targeted

finfish in general (1037.3 kg/df).

Trips landing summer flounder without scup or sea

bass were most frequent (37.0%; Table 1). The second

largest component consisted of trips landing all three

species (30.7%). Trips landing only black sea bass, only

scup, or scup with black sea bass were relatively rare

(1.9%,4.5%, and 4.1 %, respectively). Mosttrips (56.6%)

landed a muItispecies catch with at least two of the

three species.

Landings per trip of each species varied with the

associated species landed. The LPUE ofsummer flounder was highest when landed in combination with black

sea bass (975.4 kg/df), although the percentage oftrips

landing these two species without scup was 10.9% (Table

1). Highest levels of LPUE of scup and black sea bass
Shepherd and Terceiro: Summer Flounder, Scup, and Black Sea Bass Fishery 9

60 ----,---------------------~

./" SCUP

SUMMER

FLOUNDER

BLACK SEA

BASS

10

MONTH

Figure 7

Bimonthly percentage of total annual recreational catch of summer flounder, Paralichthys dentatus, scup,

Stenotomus chrysops, and black sea bass, Centropristis striata, in the Middle Atlantic Bight and southern New

England area, 1979-1990.

Table I

Mean annual landings per unit of effort (LPUE in kg/day fished) and percent occurrence for a species caught with

an associated species, based on total catch landed per trip (any trip landing summer flounder, Paralichthys dentatus,

scup, Stenotomus chrysops, and black sea bass, Centropristis striata, 1982-1990) by commercial otter trawl trips within the

Middle Atlantic Bight and southern New England area as determined from Northeast Fisheries Science Center

weighout data. Number of trips = 85,655.

LPUE

Associated species Summer flounder Scup Black sea bass

Summer flounder 434.9 345.8 49.3

(37.0%) (10.9%) (10.9%)

Scup 546.8 1,267.8 380.7

(10.9%) (4.5%) (4.1%)

Black sea bass 975.4 3,891.8 67.1

(10.9%) (4.1%) (1.9%)

Summer flounder-Scup-Black sea bass 786.6 736.3 183.6

(30.7%) (30.7%) (30.7%)
10 NOAA Technical Report NMFS 122

70 --.----------------------------,

THREE /

SPECIES .

TWO

SPECIES

""

ONE

SPECIES

10

60

w

CJ 50

z

w

040

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w

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MONTH

Figure 8

Species composition (percentage of mean commercial trawl landings, 1982-1990) per month, in the

Middle Atlantic Bight and southern New England area with a combination of one, two, or three species

from the multispecies assemblage ofsummer flounder, Paralichthys dentatus, scup, Stenotomus chrysops, and

black sea bass, Centropristis striata. The two species categories include trips landing any combination oftwo.

were obtained in trips where the two species cooccurred

without summer flounder, yet such trips were infrequent. Trips landing all three species had the largest

combination of individual species LPUE and percent

occurrence among all trips.

The number ofspecies landed per trip varied seasonally. During the winter months, trips with one, two, or

three species were all common (Fig. 8). The number of

trips landing all three species increased slightly during

the spring then fell sharply through the summer months.

Meanwhile, trips landing just one of the three species

(predominantly summer flounder) increased dramatically during the summer months, then declined by

early autumn. The percentage oftrips landing a combination of two species was relatively constant at 20-30%

throughout the year.

On a smaller spatial scale, data collected by observers

on commercial vessels provided information about species cooccurrence, including the smaller discarded fish,

within the area covered during a single otter trawl tow.

Table 2 presents the frequencies of cooccurrence and

CPUE based on the data gathered at sea. Effort in these

tows was directed primarily at summer flounder. Thirtytwo percent of tows caught summer flounder with neither scup nor black sea bass, at a rate of 489.6 kg/day

fished. In comparison, the frequency of black sea bass

in a single tow without scup or summer flounder was

only 0.5% with CPUE of 26.4 kg/day fished. Scup was

caught equally often alone (16.8% of tows), in combination with summer flounder (19.3%), or with all three

species (18.1 %). The combination of scup and black

sea bass was the least likely (3.7%), although the highest catch rates of scup (4080.0 kg/day) and black sea

bass (122.4 kg/day) were observed from this set oftows.

Similar to the weighout data, 50.7% of the tows caught

at least two of the three species. The lowest catch rates
Shepherd and Terceiro: Summer Flounder, Scup, and Black Sea Bass Fishery 11

of summer flounder and scup occurred when the two

species were caught together without black sea bass.

Table 2

Mean annual catch per unit of effort (CPUE in kg/

day fished) and percent occurrence for species caught

with an associated species, based on total catch per

tow from sea sample tow data (all observed commercial otter trawl tows catching summer flounder, Paralichthys dentatus, scup, Stenotomus chrysops, or black

sea bass, Centropristis striata, within the Middle Atlantic Bight and southern New England area, 1989-

1990. Number of tows = 1,211.

CPUE (percent occurrence)

Associated Summer Black

species flounder Scup sea bass

Summer flounder 489.6 1,224.0 105.6

(32.0%) (19.3%) (9.5%)

Scup 391.2 2,256.0 122.4

(19.3%) (16.8%) (3.7%)

Black sea bass 969.6 4,080.0 26.4

(9.5%) (3.7%) (0.5%)

Summer flounderScupBlack sea bass 710.4 1,980.0 115.2

(18.1%) (18.1%) (18.1%)

Recreational Interactions

Participants in the recreational fishery were most likely

to catch only one species per trip. For 1979-1990, 87.7%

of angler trips catching anyone of the three species

landed only one species (Table 3). Conversely, only

12.3% of the trips landed more than one species. Trips

catching only summer flounder accounted for 48.5% of

the trips whereas scup and black sea bass were caught

alone in 16.4% and 22.8% of trips. The most likely

multispecies combination was summer flounder and

black sea bass, occurring together in 7.5% oftrips. Most

ofthe harvest of each species comprised catches ofonly

one of the three species per trip. An average of 87.7%

of the summer flounder harvest was from catch of that

species only (Table 4). Similarly for scup, an average of

78.8% of the annual catch was from catch ofscup only

and 76.0% of the harvest of black sea bass was from

catch of black sea bass only.

Catch rates (number of fish per angler trip) for all

three species were highest in single-species catches.

When scup alone were caught, CPUE was 67% greater

than catch rates based on the most productive

multispecies combination (9.1/angler trip vs. 5.4/angler trip for scup/black sea bass). For black sea bass,

CPUE from single-species trips was nearly twice that of

trips in the most productive multispecies category (4.4/

angler trip vs. 2.2/angler trip for scup/black sea bass)

(Table 4). The catch rate of summer flounder from

Summer flounder catch

Summer flounder 87.7

Summer flounder + Scup 1.0

Summer flounder + Black sea bass 10.8

Summer flounder + Scup + Black sea bass 0.5

Scup catch

Scup 78.8

Scup + Summer flounder 3.5

Scup + Black sea bass 16.2

Scup + Black sea bass + Summer flounder 1.5

Black sea bass catch

Sea bass 76.0

Sea bass + Summer flounder 14.0

Sea bass + Scup 8.7

Sea bass + Summer flounder + SC\lP 1.3

Table 4

Mean percentage of annual recreational dockside

samples of catch (1979-1990) by species, accounted

for by various combinations of catches of summer

flounder, Paralichthys dentatus, scup, Stenotomus

chrysops, or black sea bass, Centropristis striata.

Catch combinations Percent of catch

Associated Summer Black

species flounder Scup sea bass

Summer flounder 3.6 4.6 2.1

(48.5%) (0.9%) (7.5%)

Scup 2.4 9.1 2.2

(0.9%) (16.4%) (3.4%)

Black sea bass 3.3 5.4 4.4

(7.5%) (3.4%) (22.8%)

Summer flounderScupBlack sea bass 2.4 2.9 1.7

(0.5%) (0.5%) (0.5%)

Table 3

Mean catch per unit of effort (CPUE as number of

fish/angler trip) and percent occurrence of species

combinations within trips from Marine Recreational

Fisheries Statistics Survey dockside sampling data (any

trips landing summer flounder, Paralichthys dentatus,

scup, Stenotomus chrysops, or black sea bass, Centropristis

striata; Middle Atlantic Bight and southern New England area, 1979-1990).

CPUE (percent occurrence)
12 NOAA Technical Report NMFS 122

trips in the single-species category was only marginally

higher than from trips in the summer flounder/black

sea bass category (3.6/angler trip vs. 3.3/angler trip).

Discussion

Fisheries for summer flounder, scup, and black sea bass

can be categorized as a winter offshore trawl fishery, an

inshore pot fishery (spring through autumn), and an

inshore recreational fishery (spring, summer, and

autumn). Summer flounder, scup, and black sea bass

are generally distributed throughout the Middle Atlantic Bight and southern New England waters but undergo seasonal migrations (Sherwood and Edwards,

1901; Finkelstein, 1971; Weber and Briggs, 1983). The

migratory patterns of all three species produce two

points in time and space where the degree of overlap in

distributions are greatest: late winter along the edge of

the continental shelf and summer in coastal waters.

Species interactions vary depending on where in the

migratory route the fishery occurs and the type of gear

used in the fishery.

The catch distributions and survey results sugge3t

that the three species disperse across the continental

shelfduring an autumn migration and reaggregate upon

reaching the offshore overwintering grounds. During

the autumn dispersal, effort is directed atsummer flounder, with less scup or black sea bass bycatch, and consequently the probability oflarge catches ofsummer flounder increases. The catch rates for all three species begins to increase during this period and peaks between

October and February when the species assemblage

reaggregates along the edge of the shelf.

Inshore migrations begin earlier in spring for summer flounder, while scup and black sea bass remain on

the overwintering grounds. During this period, when

the relative abundance ofsummer flounder in the uverwintering area declines, combined scup and black sea

bass LPUE peaks, as does the frequency of trips landing

just two of the three species. Although the catch rates

are high, this delay in the migration is brief and creates

a low annual frequency of encountering just two species. Once the spring migration begins for all three

species, catch rates within the commercial trawl fishery

decline. The overall catch rates and frequency of

cooccurrences suggest that the trawl fishery is directed

primarily at summer flounder or scup, with black sea

bass taken as bycatch. The species that dominate the

catch composition during a particular period depends

on gear configuration, variations in population abundance, and market demand.

Following the inshore spring migration, the assemblage is concentrated in coastal waters. Habitat usage

appears to differ among the three species: scup and

black sea bass frequent hard bottom and structure;

summer flounder appear to favor sandy or muddy bottom (Bigelow and Schroeder, 1953). Consequently, the

recreational and pot fisheries can target specific habitats and produce single-species catches. By the nature

of the gear, an otter trawl will integrate the catch across

all the bottom covered in a tow and is likely to produce

multispecies catches.

The nature of catches within the recreational and

commercial fisheries suggests that management measures need to be tailored to address different degrees of

multispecies interactions. Among recreational, trap, and

trawl fisheries, it is only the latter that is truly a

multispecies fishery. Although the multispecies nature

of the trawl fishery varies with season and area, the

chance of harvesting only one of the three species in a

tow averaged less than 50%. This level of interaction

may vary with relative changes in population abundance, yet changes in fishing mortality on one species

will have direct implications for all three. The species

interactions in the trap and recreational fisheries are

relatively minor and these can be considered directed

fisheries. The problem of estimating fishing mortality is

relatively simple for single species within a directed

fishery, but predicting mortality of the targeted species

following changes in regulation or perceived abundance

remains a problem. In either situation, it is apparent

that species interactions within the fisheries are dynamic and must be considered in the development of

management strategies.

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NOAA TECHNICAL REPORTS NMFS

The major responsibilities of the National Marine Fisheries Service (NMFS) are to monitor and assess the abundance

and geographic distribution of fishery resources, to understand and predict fluctuations in the quantity and distribution of

these resources, and to establish levels for their optimum use. NMFS is also charged with the development and implementation of policies for managing national fishing grounds, with the development and enforcement of domestic fisheries

regulations, with the surveillance of foreign fishing ofT U.S. coastal waters, and with the development and enforcement of

international fishery agreements and policies. NMFS also assists the fishing industry through marketing services and

economic analysis programs and through mortgage insurance and vessel construction subsidies. It collects, analyzes, and

publishes statistics on various phases of the industry.

Recently Published NOAA Technical Reports NMFS

III. Control of disease in aquaculture: proceedings of the nineteenth U.S.-Japan lIleeting on aquaculture; Ise, Mie Prefecture, Japan, 29-30 October 1990,

edited by Ralph S. Svrjcek. October 1992, 143 p.

112. Variability of telllperature and salinity in the

Middle Adantic Bigbt and Gulf of Maine, by Robert L.

Benway, Jack W. Jossi, Kevin P. Thomas, and Julien R.

Goulet. April 1993, 108 p.

113. Maturation of nineteen species of finfish off the

northeast coast of the United States, 1985-1990, by

wretta O'Brien,Jay Burnett, and Ralph K. Mayo. June 1993, 66 p.

114. Structure and historical changes in the

ground.6.sh cOlllplex of the eastern Bering Sea, by

Richard G. Bakkala. July 1993,91 p.

115. Conservation biology of elaslllobranchs, edited

by Steven Branstetter. September 1993, 99 p.

116. Description of early larvae of four northern

California species of rockfishes (Scorpaenidae:

Sebastes) frOIll rearing studies, by Guillermo Moreno.

November 1993, 18 p.

117. Distribution, abundance, and biological characteristics of groundfish off the coast of Washington,

Oregon, and California, 1977-1986, by Thomas A. Dark

and Mark E. Wilkins. May 1994, 73 p.

118. Pictorial guide to the groupers (Teleostei: Serranidae) of the western North Adantic, by Mark Grace,

Kevin R. Rademacher, and Mike Russell. May 1994, 46 p.

119. Stocks of dolphins (Stenella spp. and Delphinus delphis) in the eastern tropical Pacific: a

phylogeographic classification, by Andrew E. Dizon, William F. Perrin, and Priscilla A. Akin. June 1994, 20 p.

120. Abundance and distribution of ichthyoplankton along an inshore-offshore transect in

Onslow Bay, North Carolina, by Allyn B. Powell and

Roger E. Robbins. June 1994,28 p.

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