SURVEY CATCH (numbors)

i °
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TEMPERATURE,

we, 1975
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TEMPERATURE,

Figure6. Catchesof Atlantic mackerel versus bottom temperature
from spring bottom trawl surveys conducted by the
Northeast Fisheries Science Center for 1970, 1975,
and 1981. (Null tows are not included in these plots.)

Page 9
Table 2. Arrival date, departure date, duration of stay, and
average catch per angler — all from interviews ~ for
the Atlantic mackerel spring recreational fishery by
state and year during 1979-87
State Year Arrival Departure Dura- Avg.
Date Date tionof Catch
Stay per
Gays) Angler
(i fish)
Virginia 1979
1980
1981
1982
1983 03/20 322.0
1984 4/14 0.8
1985 03/31 12.8
1986 03/05 03/31 27 95.4
1987 03/28 13.2
Maryland 1979
1980
1981
1982
1983 03/17 04/29 13 (175.5
1984 04/07 05/22 16 60.5
1985
1986 05/12 206.7
1987 o4/11 O42 2 269
Delaware 1979 oay15 05/28 14 126.2
1980 4/19 230.9
1981
1982
1983 03/02 04/03 33 50.0
1984 Os/1l 04/29 19 293.9
1985 04/20 141.7
1986 4/12 04/20 9 100.6
1987 03/28 13.2
New Jersey 1979 04/29 500.0
1980 04/22 04/23 2 619
1981 o41l 05/13 34 (137.3
1982 04/16 05/02 7 1225
1983 04/09 04/30 22 192.2
1984
1985 04/07 188.0
1986 04/12 05/04 23 14.8
1987 ogi 05/09 2s 746
New York 1979 05/15 84.4
1980 05/31 06/01 2 59.6
1981 05/25 05/09 15 11.25
1982 05/16 13.0
1983
1984 05/13 5/19 7 14
1985 04/27 04/28 2 145.8
1986
1987 05/03 05/09 7 256.1



Page iii

TABLE OF CONTENTS

SIANNNH

12

References Cited .. 12

LIST OF TABLES

Table 1. Recreational catch, age 3+ stock size, average spring inshore surface temperature,
average spring bottom temperature, and March wind stress data used in this study ...

Table 2. Azrival date, departure date, duration of stay, and average catch per angler — all from interviews —
for the Atlantic mackerel spring recreational fishery by state and year during 1979-87 ......

Table 3. Results of correlation analyses of recreational catch versus stock size, average spring
inshore surface temperature, and meridional March wind stress during 1979-87

LIST OF FIGURES

Figure 1. Map of the eastern United States from North Carolina to Maine with place names mentioned
in the text, and with the 200-m isobath .
Figure 2. Average March-April bottom water temperature for the Southem New England -
Mid-Atlantic region, and average spring inshore surface water temperature for the New Jersey -
Long Island area, from bottom trawl surveys conducted by the Northeast Fisheries Science
Center during 1968-87 ......
Figure 3a. Catches of Atlantic mackerel from spring bottom trawl surveys conducted by the
Northeast Fisheries Science Center from Cape Hatteras, North Carolina, to Nova Scotia
during 1970-75
Figure 3b. Catches of Atlantic mackerel from spring bottom trawl surveys conducted by
Northeast Fisheries Science Center from Cape Hatteras, North Carolina,
to Nova Scotia during 1976-81
Figure 3c. Catches of Atlantic mackerel from spring bottom trawl surveys conducted by the
Northeast Fisheries Science Center from Cape Hatteras, North Carolina, to
Nova Scotia during 1982-87
Figure 4. Annual catches of Atlantic mackerel from spring bottom trawl surveys conducted by
the Northeast Fisheries Science Center from Cape Hatteras, North Carolina, to
Nova Scotia during 1970-87 Catches are expressed as percent of total catch by latitude,
collapsed over longitude........
Figure Sa. Surface temperature contours from a spring bottom trawl survey conducted by the
Northeast Fisheries Science Center from Cape Hatteras, North Carolina,
to Georges Bank in 1981 .....-.-.--. -+--+
Figure 5b. Surface temperature contours from a spring bottom trawl survey conducted by the
Northeast Fisheries Science Center from Cape Hatteras, North Carolina,
to Georges Bank in 1982 .....
Figure 6. Catches of Atlantic mackerel versus bottom temperature from spring bottom trawl surveys
conducted by the Northeast Fisheries Science Center for 1970, 1975, and 1981 .....
Figure 7. Recreational catch versus stock size for 1979-87 with linear regression line, computed
without the 1981 data point ....
Figure 8. Recreational catch versus average surface temperature from spring bottom trawl surveys for
1979-87 with linear regression line
Figure 9. Recreational catch versus meridional component of March wind stress for 1979-87
with linear regression line



[Nat. Mar. Fish. Serv., Northe. Fish. Crr.,] Woods Hole
Lab. Ref. Doc. No. 85-13. 5 pp.

Sette, OE. 1950. Biology of the Atlantic mackerel
(Scomber scombrus) of North America. Part 2. Migra-
tions and habits. Fish. Bull, U.S. 51: 251-358.

Sette, O.E., and WH Needler. 1934. Statistics of the
mackerel fishery off the coast of North America. U.S.
Dept. Comm. Invest. Rep. No. 19. 48 pp.

Swanson, R.L., and C.A. Parker. 1988. Physical environ-
mental factors contributing to recurring hypoxia in the
New YorkBight. Trans. Amer. Fish. Soc. 117: 37-47.

Swanson, R.L., and RL. Zimmer. 1990. Meteorological
conditions leading to the 1987 and 1988 washups of
floatable wastes on New York and New Jersey beaches
and comparison of these conditions with the historical
record. Estuar. Coast. Shelf Sci. 30: 59-78.

U.S. Department of Commerce. 1984. Marine recreational
fishery statistics survey: Adantic and Gulf Coasts,
1979-1980. Nar. Mar. Fish. Serv. Curr. Fish. Stat. No.
8322. 239 pp.

Page 13

U.S. Department of Commerce. 1985a. Marine recrea-
tional fishery statistics survey: Atlanticand Gulf Coasts,
1981-1982. Nar. Mar. Fish. Serv. Curr. Fish. Stat. No.
8324. 215 pp.

U.S. Department of Commerce. 1985b. Marine recrea-
tional fishery statistics survey: Atlantic and Gulf Coasts,
1983-1984. Nar. Mar. Fish. Serv. Curr. Fish. Stat. No.
8326. 222 pp.

U.S. Department of Commerce. 1986. Marine recreational
fishery statistics survey: Atlantic and Gulf Coasts,
1985. Nat. Mar. Fish. Serv. Curr. Fish. Star. No. 8327.
130 pp.

U.S. Department of Commerce. 1987. Marine recreational
fishery statistics survey: Atlantic and Gulf Coasts,
1986. Nar. Mar. Fish. Serv. Curr. Fish. Stat. No. 8392.
127 pp.

U.S. Department of Commerce. 1991. Marine recreational
fishery statistics survey: Atlantic and Gulf Coasts,
1987-1989. Nar. Mar. Fish. Serv. Curr. Fish. Star. No.
8904. 363 pp.

FY UL S. GOVERNMENT PRINTING OFFICE: 2992--500-032—=40005


Page 5

Fa ee eT We ee Se pari ri
JEL
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3
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MACKEREL SPRING 1979

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Ny L

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SPRING 197

REL SPARE

a

Figure 3b. Catches of Atlantic mackerel from spring bottom trawl surveys conducted by the Northeast Fisheries Science Center from

Cape Hatteras, North Carolina, to Nova Scotia during 1976-81.



Page 2

Mackerel are sensitive to temperature both in terms of
physiological and behavioral responses and also inrelation
to timing of migration and spawning activity (Sette 1950;
Olla er al. 1976; Anderson and Almeida 1977; Berrien
1982; Murray et al. 1983). Laboratory and field studies
have shown that mackerel are intolerant of water tempera-
tures less than 5-6°C, or greater than about 15-16°C (Ola ez
al, 1976; Overholtzand Anderson 1976). During the winter
and early spring, mackerel are distributed in the warmer
waters along the shelf-slope break from Hudson Canyon to
Cape Hatteras (Sette 1950; Anderson and Almeida 1977).
In April and early May, they begin a northward and inshore
migration to form spawning aggregations. There are two
spawning contingents (Sette 1950): (1) a southern contin-
gent that spawns off New Jersey and New York, and (2) a
northerncontingent that spawns in the Gulf of St. Lawrence.
Meteorological events or regional climatic conditions are
probably important in determining the range, timing, and
extent of these inshore spring migrations for the southern
contingent (Murray eral. 1983). Thus, low temperatures in
the spring could delay inshore migrations significantly and
also affect their duration (Murray 1984). Changes in the
temperature regime of the inshore area could be caused by
the frequency or intensity of winter or spring storms, colder-
than-normal winters, shifts inwater masses, variations from.
normal wind patterns, and/or other factors.

The purpose of this study is to investigate changes in
the distribution and recreational catch of Atlantic mackerel
from the Northwest Atlantic stock in relation to environ-
mental conditions. Relative abundance data from spring
bottom trawl surveys conducted by the Northeast Fisheries
Science Center (NEFSC) during 1968-87, wind stress esti-
mates forthe Mid-Auantic region, and catch-effort informa-
tion from recreational fishery surveys conducted by the
National Marine Fisheries Service (NMFS) were utilized.
Since none of these data were collected from studies that
were specifically designed to monitor changes in mackerel
distribution and catch, they are used in anexploratory sense,
with the hope of defining important relationships that are
broad enough inextent to be clearly defined. Additionally,
the results should be useful for identifying possible causal
factors and the limitations of the fisheries and environmen-
tal data.

METHODS
INITIAL HYPOTHESES.

Prior to attempting analysis, we formulated a set of
working hypotheses to focus our work so that our study
would not resemble a random search of all possible vari-
ables to obtain the best model fit. To facilitate this
approach, we discussed a conceptual model of the mackerel
migration, its environmental determinants, and implica-
tions for recreational fishing success. We felt that spring

inshore temperature was probably one of the dominant
factors responsible for changes in mackerel distribution.
This was based on previous work suggesting that mackerel
were intolerant of temperatures less than about 5-6°C (Olla
eral. 1976), and that the spring behavioral and physiologi-
cal changes such as aggregation for spawning and matura-
tion of gonads were keyed at least partly to the thermal
regime during this time period.

We identified the need for a mechanistic model of
factors influencing nearshore conditions in the spring.
Regional meteorolog=", variation in seasonal clirnatic fac-
tors, and changes in coastal oceanography may all be
important in determining the sp:-ng temperature regime off
the Mid-Atanticregion. Forexample, southward winds off
the Virginia Capes in the early spring could cause cold
water to be trapped along the shore, ora severe spring storm
off New Jersey could mix cold nearshore bottom water with
warmer surface waters. We used meridional (north-south)
wind stress, a measure of seasonal wind direction and
intensity, as a proxy variable for many of the aforemen-
tioned processes. We also were interested in finding out if
recreational catch was related to stock size.

DATA

After formulating these initial hypotheses, we at-
tempted a series of correlation analyses, relating recre-
ational catch to stock size, water temperature, and wind
stress. Temperature data were collected during each cruise
and at almost every station of the NEFSC’s spring bottom
trawl surveys conducted from 1968 through 1987. The
design and protocol of these annual research surveys have
been described in detail by Grosslein (1969) and Azarovitz
(1981). The surveys are based ona stratified randomdesign
with appropriate statistical methods and sampling sched-
ules applied throughout. The Mid-Auantic survey starts in
mid-March each year, the region has been sampled consis-
tently eachspring. Temperature records from these cruises
were used to produce two different sets of data: (1) average
‘bottom temperature for the entire Southern New England -
Mid-Atlantic area representing minimum winter tempera-
ture conditions, and (2) average surface temperature for the
inshore area from Cape May, New Jersey, to Long Island,
New York, representing spring conditions (Table 1; Figure
2).

Monthly mean values of the meridional component of
wind stress for a standard grid point representative of the
central portion of the Middle Adantic Bight (39°N, 75°W)
‘were acquired from the wind-driven flow indices generated
by the NMFS's Pacific Fisheries Environmental Group, and
‘based on the surface atmospheric pressure analyses of the
U.S. Navy Fleet Numerical Oceanographic Center. The
wind stress data were used in correlation analyses to see if
this measure of regional climatic energy was appropriate
for explaining any of the variation in recreational catch that
was observed over the 1979-87 period.


Page 1
ABSTRACT

The relationship between the spring distribution of Adlantic mackerel (Scomber scombrus), environmental factors, and
the recreational fishery for mackerel in the Mid-Atlantic - Southern New England region was investigated. The Northwest
Adantic stock of Atlantic mackerel is highly migratory, with the southern spawning contingent showing a pronounced
inshore and northward migration during the spring and early summer, and the northern spawning contingent moving north
into the Gulf of St. Lawrence at this time. We examined catch distribution maps constructed from spring research vessel
bottom trawl surveys; results indicated that the center of abundance of the stock shifts toward the south in years with cool-
to-moderate shelf temperatures and shifts northward in warmer years. Catches of mackerel in the Northeast Fisheries
Science Center's spring bottom trawl surveys are usually at bottom water temperatures of 5°C or greater; mackerel tend
to actively avoid cooler water. Recreational catch in the Mid-Atlantic - Southem New England region is positively, but
weakly, correlated with stocksize, and is probably highly influenced by the thermal regime inthe early spring. Recreational
catch may also be related to wind direction and intensity during March; this is probably an indication that regional

meteorological conditions heavily influence the inshore environment at this time.

INTRODUCTION

Atlantic mackerel (Scomber scombrus) in the North-
west Atlantic have been fished commercially along the
coast of the eastern United States since the early 1800s
(Sette and Needler 1934; Hoy and Clark 1967; Anderson
and Paciorkowski 1980; Overholtz and Parry 1985; Figure
1). Since 1960, a major commercial and recreational
fishery developed in the Mid-Atlantic (Massachusetts to
Virginia) region (Figure 1) during the winter and spring
when the transient mackerel stock is abundant there. A
large distant-water fleet began fishing for mackerel in the
Mid-Atlantic region in the late 1960s, and arnual catches
averaged 310,000 metric tons (mt) during 1970-76 (Ander-
sonand Paciorkowski 1980). These large catches were not
sustainable and the stock collapsed. Catches declined
dramatically, and coincident with extension of U.S. man-
agement responsibility to 200 miles offshore, the Mid-
Adantic Fishery Management Council (MAFMC) estab-
lished controls on the fishery in the early 1980s under
authority of the Magnuson Fishery Conservation and Man-
agement Act. During the 1980s, the MAFMC utilized
annual catch quotas, established a target minimum spawn-
ing stock size (600,000 mt), and — to the extent possible -
- minimized foreign fishing on the mackerel stock to
enhance the spring recreational fishery.

During the late 1960s, an intense recreational fishery
for mackerel also developed in the springtime. Catches
from this fishery have been highest along the nearshore
areas of New Jersey and New York, locations where the fish.
formspawning congregations in Apriland May (Sette 1950;
Murray er af 1983). Recreational catchdeclined in the late
1970s and early 1980s coincident with the collapse of the
stock, but clear trends before that time are difficult to
discern because of sparse data.

The waters on the Mid-Atlantic - Souther New En-
gland continental shelf exhibit a large seasonal cycle in
temperature (Colton and Stoddard 1972; Mountain and
Holzwarth 1989). In winter, the water colurm is vertically

b

if es
Figure 1. Map of the eastern United States from North Carolina

to Mainz with place names mentioned in the text, and
with the 200-m isobath.

wellmixed with temperatures of less than4°C near the coast
and increasing to above 8°C near the shelf edge. In the
spring, the surface layers begin to warm and temperatures
continue to increase through the summer, with the warming
Progressing from south to north, The annual maximum
surface-layer temperatures are above 25°C over the south-
em part of the shelf and decrease to the north, with
maximum values south of Nantucket of about 18°C. In the
early fall, the surface-layer temperature begins to decrease,
and cooling continues until reaching minimum values in
late February or early March (Han and Niedrauer 1981).


{continued from inside front cover)

64. The Shell Disease Syndrome in Marine Crustaceans. By Carl J. Sindermann. February 1989. v + 43 p., 5 figs.,
2 tables. NTIS Access. No. PB89-162523/AS.

65. Stock Assessment Information for Pollock, Pollachius virens (L.),in the Scotian Shelf, Georges Bank, and Gulf
of Maine Regions. By Ralph K. Mayo, Stephen H. Clark, and M. Christina Annand. April 1989. vi + 14 p., 6 figs.,
14 tables. NTIS Access. No. PB90-120676/AS.

66. Guidelines for Estimating Lengths at Age for 18 Northwest Atlantic Finfish and Shellfish Species. By Judith
A. Pentilla, Gary A_Nelson, and John M. Burnett, Il. May 1989. iii + 39 p., 18 figs., 19 tables. NTIS Access. No., PB90-
120675/AS.

67. Response of the Habitat and Biota of the Inner New York Bight to Abatement of Sewage Sludge Dumping.
Second Annual Progress Report -- 1988. By Environmental Processes Division, Northeast Fisheries Center. July
1989. vii + 47 p., 39 figs., 11 tables, 3 app. NTIS Access. No. PB90-125444/AS.

68. MARMAP Surveys of the Continental Shelf from Cape Hatteras, North Carolina, to Cape Sable, Nova Scotia
(1984-87). Atlas No. 3. Summary of Operations. By John D. Sibunka and Myron J. Silverman. July 1989. iv + 197
P., 36 figs., 2 tables. NTIS Access. No. PB90-160656/AS.

69. The 1988 Experimental Whiting Fishery: A NMFS/Industry Cooperative Program. By Frank P. Almeida,
Thurston S. Burns, and Sukwoo Chang. August 1989. v + 16 p.,9 figs., 11 tables, 1 app. NTIS Access. No. PB9O-
160664/AS.

70. Summer Distribution of Regulated Species on Georges Bank with Reference to the 1988 Experimental
Whiting Fishery. By Frank P. Almeida, Sukwoo Chang, and Thurston S. Bums. September 1989. v+ 25 p., 74 figs.,
l table. NTIS Access. No. PB90-206525/AS.

71, Allocation of Statewide-Reported MRFSS Catch and Landings Statistics between Areas: Application to
Winter Flounder. By FrankP. Almeida. September 1989. v+ 18 p., 5 figs., 6 tables, 2 app. NTIS Access. No. PB90-
246745.

72. Status of the Fishery Resources off the Northeastern United States for 1989. By Conservation and Utilization
Division, Northeast Fisheries Center. December 1989. iv + 110p., 5Ofigs., 93 tables. NTIS Access. No. PB90-170622/
AS.

73. Surface and Bottom Temperature Distribution for the Northeast Continental Shelf. By David G. Mountain
and Tamara J. Holzwarth. December 1989. iii + 32 p., 31 figs. NTIS Access. No. PB90-252172/AS.

74. Shell Disease of Crustaceans in the New York Bight. By C.J. Sindermann (chair.), F. Csulak (EPA coord.), TK.
Sawyer (rapp.),R-A. Bullis, D.W. Engel, B.T. Estrella, E.J. Noga, J.B. Pearce, J.C. Rugg, R. Runyon, J.A. Tiedemann,
and R-R. Young. December 1989. vii + 47 p.,7 figs., 4 tables, 4 app. NTIS Access. No. PB90-195058/AS.

75. An Indexed Bibliography of Northeast Fisheries Center Publications and Reports for 1988. By Jon A. Gibson.

76. Finfish Maturity Sampling and Classification Schemes Used during Northeast Fisheries Center Bottom
Trawl Surveys, 1963-89. By Jay Burnett, Loretta O’Brien, Ralph K. Mayo, Jeffrey A. Darde, and Margot L. Bohan.
December 1989. iii+14 p., 11 tables, 1 app. NTIS Access. No. PB91-128389/AS.

77. Shell Disease among Red Crabs Inhabiting Submarine Canyons of the New York Bight. By Randall R. Young.
December 1989. iii+9 p., 18 figs., 5 tables. NTIS Access. No. PB90-194762/AS.

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during 1977-88. By Sukwoo Chang. October 1990. v+130 p., 246 figs. NTIS Access. No. PB91-160846.


Page 4

Be cht “fe Ces PI eb tt a t rf
be Na + Aye e te W I

bee | pope fS | yy

Ry ° ; 8 : toh, ees

| Sscf f al hats
, . +

win y
Te ae
' Vere Prom

PIRI fia. , rf Ry .
a ae ee aes

Jt} ttt

6

MACKEREL SPRING 1973

MECKEAEL SPRING.

a,

JZ
ct G ¢

ze

i Pett ded td

Ey ee a BB Ov
Noe | BNI)

by 1
ie
Pag tt

TACSEREL SPAING 1870
MACKEREL SPRING 1873
MACKEREL SPRING 1872

Figure 32. Catches of Atlantic mackerel from spring bottom trawl surveys conducted by the Northeast Fisheries Science Center from

|p tt ttt Bt AI th I

Cape Hatteras, North Carolina, to Nova Scotia during 1970-75.


PB92-160209

NOAA Technical Memorandum NMFS-F/NEC-85

Factors Influencing Spring Distribution,
Availability, and Recreational Catch
of Atlantic Mackerel (Scomber
scombrus) in the Middle Atlantic

and Southern New England Regions

U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
National Marine Fisheries Service
Northeast Region
Northeast Fisheries Science Center
Woods Hole, Massachusetts

August 1991

REPRODUCED BY
U.S. DEPARTMENT OF COMMERCE

NATIONAL TECHNICAL INFORMATION SERVICE
SPRINGFIELD, VA 22161


values for these last three measures of availability are
imprecise, because daily interviews were not conducted,
but they should give some indication of trends by state.

The Northwest Atlantic mackerel stock has been stud-
ied extensively for five decades (Sette 1950; Anderson and
Paciorowski 1980). Recent analytical assessments (Ander-
son and Paciorowski 1980), which have been updated
annually, provide a time series of estimates of stock size
from 1962 to 1987. Since most fish caught and kept by
recreational anglers tend to be large (ie., greater than 30
cm) (Christensen and Clifford 1980), age 3+ population
size (in numbers of fish) was used as an estimate of
exploitable stock for the recreational fishery. These esti-
mates (Table 1) were available from a recent update of a
virtual population analysis that was described in detail in
Anderson and Paciorowski (1980).

RESULTS

Bottom temperature data from NEFSC spring bottom
trawl surveys for 1968-87 show a period of pronounced
warming in the 1970s followed by arelatively stable cooler
trend in the 1980s (Figure 2). Temperatures reached a high
of 9.8°C in 1973, dropped to 5.8°C in 1978, and hovered
around 6.5°C during the 1980s. Plots of spring trawl survey
mackerel catches indicate that in 1970 and 1971 mackerel
were distributed along the shelf-slope break, but during
1972-76 were found in shallower water and further north
(Figure 3a,b; Anderson and Almeida 1977). This shift in
distribution coincides with the warmer temperatures mea-
sured on the bottom trawl surveys during the 1972-76 period
(Figure 2; Anderson and Almeida 1977). During the iate
1970s, mackerel were again found in the shelf-slope break
region. During 1978, the year with the lowest trawl-survey
bottom temperature, the stock was distributed along the
outer shelf-slope area and in the southemhalf of the Middle
Atlantic Bight. Incontrast, during 1973 and 1974, the bulk
of the stockhad shifted much farther to the north, with some

of the largest catches being taken on eastem Georges Bank. *

These patterns are clearer if the information is con-
verted to percent of catch by one degree of latitude,
collapsed over longitude (Figure 4). In the early to middle
1970s, very little of the stock appeared to be in southem
waters, while in the late 1970s, the stock seemed to be
spread out over a much greater area, with a major portion
of itsouth of 38°N latitude (Figure 4). Formost of the 1970s,
the mackerel stock was confined to the area between 38° and
40°N latitude.

In the 1980s, it appears that Atlantic mackerel were
generally in shallower water, as opposed to being primarily
along the shelf-slope break in the 1970s. During the 1980s,
the mackerel stock occupied more of the continental shelf
from 35° to 40°N latitude (Figures 3b,c). In general, there
seemed to be a split in distributionat 37°-38°N, with part of
the stock to the north and part to the south.

Page7

Figure 4. Annual catches of Atlantic mackerel from spring
bottom trawl surveys conducted by the Northeast
Fisheries Science Center from Cape Hatteras, North
Carolina, to Nova Scotia during 1970-87. Catchesare
expressed as percent of total catch (in numbers of
fish) by latitude, collapsed over longitude.

Temperature patterns on the shelf, developed from the
spring trawl survey data base, were useful for interpreting
changes in mackerel distribution and recreational catches
for 1981 and 1982. In 1981, recreational catch rates off the
New Jersey coast were the highest in the 1979-87 period
(Table 2), coincident with the warm shelf temperatures that
‘were present in that region at the time (Figure Sa). In 1982,
when recreational catches were the lowest in the 1979-87
period, shelf temperatures during the spring were noticably
colder than in 1981 (Figure 5b). The overall distribution of
the mackerel stock in these years was also quite different
with most of the fish found much farther south in 1981
(Figures 3a,b).

Survey catch data ard bottom temperatures from spe-
cific sites indicate that the largest mackerel catches occur
at temperatures greater than about 5°C. Plots of mackerel
catches from spring surveys in 1970, 1975, and 1981
illustrate that mackerel were consistently captured at bot-
tom temperatures greater than 5°C, and virmally all the
larger catches (ie., greater than 100 fish) occurred at
temperatures greater than 6°C (Figure 6).

Anexamination of MRESS intercept survey catchdata
from the recreational fishery for 1979-87 suggested some
interesting generalities about the spring mackerel fishery,
eventhough there are some inconsistences insampling over
this time period. Summaries of the Virginia and Maryland
fisheries indicate that when the fish are available, they
usually arrive in late March in Virginia and mid-April in
Maryland (Table 2). Little, if any, catch occurred from
1979 to 1982 in either of these states; however, sampling in
March was poor for the period. The fishery off Delaware,
New Jersey, and New York is much more stable from year
to year, and catch per unit of effort (CPUE) is more
consistent than in southern waters (Table 2). Fish appar-
ently arrive inmid-April off Delaware and New Jersey, and
the duration of the migration is longer there. CPUE off


Page 6

Ro Cy WR
hn
Ss

SPRING 1982

Ry

a

he ca

1986

ee eee CTS
oO 4.

Nae

ej} 1b +t A

pg aaa 3
Ns

NG 1984

MACKEREL SPRING 1987

MACKEREL SPRL

<a fp}—=ft——1— 1-14

$2 REA} 4+ AA

et

8} tt tt tI

ae 148

1

Figure 3c. Catches of Atlantic mackerel from spring bottom trawl surveys conducted by the Northeast Fisheries Science Center from
Cape Hatteras, North Carolina, to Nova Scotia during 1982-87.


Table 1. Recreational catch, age 3+ stock size, average spring
inshore surface temperature, average spring bottom
temperature, and March wind stress data used in this

study
Year Recreational ~Age3+ Average Average March
Catch Stock Spring Spring Wind
(000s mt) Size Inshore Bottom — Stress
(milion Surface Temp. (000s
fish) Temp. cor dyn
car ar)’
1962 3565.0 531.0
1963 3,981.0 635.0
1964 4343.0 705.0
1965 4292.0 645.0
1966 4535.0 606.0
1967 4,498.0 629.0
1968 1781.0 939.0 255 632
1969 13,0500 1,898.0 250 629
1970 16,039.0 4,853.0 6127.73
1971 16426.0 4252.0 391 7.09
1972 15,588.0 3,762.0 494 8.43
1973 10,7230 2,886.0 476 9.79
1978 7630.0 2,171.0 632 922
1975 5,190.0 1,560.0 539 7.03
1976 42020 1536.0 598 8.01
1977 522.0 1399.0 489 9 624
1978 6571.0 1204.0 408 (S81
1979 35880 1,017.0 $35 647 4
1980 2,364.0 815.0 S17 6.58 -65
1981 8,505.0 837.0 5.67 647-556
1982 1,162.0 683.0 433° 624 7
1983 3,280.0 664.0 533. 687 = -227
1984 26180 1,385.0 452. 679-216
1985 32870 5,136.0 507 6.90 “86
1986 3943.0 4238.0 6.00 7.08 u
1987 $567.0 3,653.0 575 6.63 93

*From NEFSC spring bottom traw! surveys.

*Meridional component of wind stress. Positive values are porthward.
Dats from NMFS Pacific Fisheries Environmental Group based on
U.S. Navy surface pressure analysis.

Mackerel catches from the spring bottom trawl surveys
were plotted on maps of the region to evaluate changes in
distribution over the 1970-87 period (Figures 3a-c). Al-
though these research surveys were not specifically de-
signed for sampling pelagic fishes such as mackerel, they
are still useful for defining fish distributions. We were
interested in whether the distribution patterns of the North-
west Atlantic mackerel stock had changed over these two
decades because stock size had undergone drematic fluc-
tuations over this period and temperatures were much more
variable during the 1970s. These data were also converted
to percent of catch by one degree of latitude on an armual
basis and plotted to give another perspective on changes in
the distribution of mackerel (Figure 4). Spring survey
temperature data were used to produce contour maps for the
area from Cape Hatteras, North Carolina, to southem
Georges Bank for 1981 and 1982 in order to compare the
years with the highest and lowest recreational catch (Fig-
ures Sa,b). In addition, trawl survey bottom temperature

Page 3

Temperature (C)

76 78 80 S2 84 66 88

Year

Figure 2. Average March-April bottom water temperature (°C,
dashed line) for the Southem New England - Mid-
Atlantic region, and average spring inshore surface
water temperature (°C, solid line) for the New Jersey -
Long Island area, from bottom trawl surveys conducted
by the Northeast Fisheries Science Center during 1968-
87.
and catch of Atlantic mackerel were plotted for 1970, 1975,
and 1981 (Figure 6) to ascertain if any mackerel were
caught at temperatures less than their normal lower toler-
ance limit of $°C (Ollla er al. 1976). Since a previous study
indicated that few mackerel are ever caught below 5°C
(Overholtz and Anderson 1976), we only picked a few years
in the time series to confirm this assertion.

A telephone recall survey of the recreational fishery
was conducted in 1960, 1965, and 1970 to estimate recre-
ational catch of Atlantic mackerel (Clark 1967; Deuel and
Clark 1968; Deuel 1973). From 1979 to present, the NMFS
has conducted the Marine Recreational Fishery Statistics
Survey (MRFSS), a program of complementary telephone
and intercept (on-site angler interviews) surveys that pro-
vides catch and effort estimates for the coastwide recre-
ational fishery (U.S. Departmentof Commerce 1984, 1985a,
1985b, 1986, 1987, 1988). The intercept portion of the
survey collects information on the numbers, weights, and
length frequencies of the catches.

Direct estimates of recreational catch were only avail-
able for 1960, 1965, 1970, and 1979-87; the rest of the years
were interpolated (Anderson 1981). We therefore re-
stricted our analyses to recent years, 1979-87, when direct
estimates of recreational catch were available and consis-
tent data collection procedures had been employed. Inrer-
view sampling data from the MRESS, 1979-87, were exam-
ined to identify trends in the recreational fishery. March,
April, and May interviews of fishermen in the Mid-Atlantic
region were studied to determine average catch per angler,
arrival date (date of first interview), departure date (date of
last interview), and duration of stay (days between first and
last interview) on 1 state-by-state basis (Table 2). The


PB92-160209

OATMOSAry., .
og s NOAA Technical Memorandum NMFS-F/NEC-85
g %,
if
F| g
‘gl JS This TM series is used for documentation and timely communication of preliminary results,
Py iS interim reports, or special purpose information, and has not undergone external scientific
>, Si review.
“Warmer OF ©

Factors Influencing Spring Distribution,
Availability, and Recreational Catch
of Atlantic Mackerel (Scomber scombrus)
in the Middle Atlantic
and Southern New England Regions

William J. Overholtz', Reed S. Armstrong?, David G. Mountain’,
and Mark Tercerio*

"Woods Hole Lab., National Marine Fisheries Service, Woods Hole, MA 02543-1097
Narragansett Lab., National Marine Fisheries Service, Narragansett, RI 02882

U. S. DEPARTMENT OF COMMERCE
Robert A. Mosbacher, Secretary

National Oceanic and Atmospheric Administration
John A. Knauss, Administrator
National Marine Fisheries Service
William W. Fox, Jr., Assistant Administrator for Fisheries
Northeast Region
Northeast Fisheries Science Center
Woods Hole, Massachusetts

August 1991


Page 10

Table 3, Results of correlation analyses of recreational catch versus stock size, average spring inshore surface temperature, and

meridional March wind stress during 1979-87

Independent Variable r r F P Significance D-W
Level" Statistic

Stock size® 0.57 0.32 2.863 0.1416 NS 1.694
Surface temperature 0.68 0.47 6.116 0.0526 * 2572
Wind stress 0.72 0.52 7.515 0.0284 * 1.283
Surface temperature
& stock size 071 0.50 2978 0.1264 NS 2.675
Surface temperature
& stock size 0.84 O71 6.089 0.0457 * 2.098
Surface temperature
& wind stress 0.93 0.86 18.293 0.0028 ” 2.466

*P <0.05=*; P <0.01 = **; and not significant = NS.
* Durbin-Watson statis test of autocorrelation.
* Excluding the 1981 data point.

Migration of mackerel in the Northwest Atlantic. Bottom.
trawlsurvey data fromselected years indicate thatmackerel
are seldom captured at temperatures less than 5°C, and
almost all of the larger catches that occur in surveys are
taken at bottom temperatures greater than 6°C (Figure 6). A
previous study summarizing survey data for all stations in
the Southern New England - Mid-Atlantic region for 1968-
‘76 (N=777) showed that 46 percent of the stations that were
occupied had bottom temperatures less than 5°C, and only
five percent of the stations where catches were made were
below 5°C (Overholtzand Anderson 1976). Thus, mackerel
in the Mid-Atlantic region apparently seek temperature
conditions during the winter and spring that may limit their
spatial distribution. Laboratory studies show that swim-
ming speeds of mackerel increase at low temperature,
suggesting that this 5°C threshold is important (Ola er al.
1976).

Results from correlation analyses suggest that spring
Tecreational catches in the Mid-Auantic region are posi-
tively related to inshore surface temperatures in the late
March to mid-April period. This means that a cool spring
is likely to inhibit the northward and inshore migration of
mackerel, resulting in a smaller recreational catch. Previ-
‘ous work by other researchers suggested that Julian arrival
dates of mackerel at specific points along the Mid-Atlantic
coast were negatively related to March surface temperature.
(Murray 1984). The study also found that duration of stay
at these coastal locations was negatively related to arrival
date. Thus, if mackerelarrive early ata point along the coast
due to favorable (warm) surface-water temperatures, they
will likely stay longer. This should have a positive impact
on recreational catch because the fish will be available

inshore fora longer period of time and thusmore vulnerable
to exploitation by anglers.

The positive relationship between temperature and
recreational catch may only be valid over a short range in
temperature. During the 1980s, the temperature remained
ratherstable, albeit rising (Figure 2). Itappears thata major
warming trend, such as occurred in the early tomid 1970s,
may cause the stock to shift too far north, causing recre-
ational catch from Virginia to New Jersey todecline (Figure
3a; Table 1). Although catch estimates for 1974-76 are
uncertain, they suggest that during a period when tempera-
tures were higher than observed in the 1980s, the recrea-
tional fishery waned along the entire Mid-Adantic region
(Table 1).

The negative relationship between recreational catch
and March wind stress that was found in the correlation
study suggests that meteorological events that occur just
prior to and during the arrival of the fish may be important.
Other studies have indicated that seasonal winds have a
major impact on the coastal oceanography of this region.
(Swanson and Parker 1988; Swanson and Zimmer 1990).
Southward winds during March may serve to retain warm
surface water near the shore, thereby preserving optimal
thermal conditions and prolonging fish availability to the
recreational fishery. We caution that the relationship
between catch and wind stress is a proxy for several factors
that may influence the thermal pattern in the spring in this
region. Factors such as river discharge, frequency of storm
events, and other environmental conditions may also be
important and are certainly very prominent in this region
(Swanson and Parker 1988). Ina given year, however, it
appears that recreational catch is probably related to the


uP

Page 12

Atlantic region. Other factors may be important, and
certainly the underlying mechanisms causing shifts in
distribution and availability are still an enigma. A more
thorough analysis of available data would certainly be
valuable, especially if fairly detailed sets of envirormnental
observations could be matched with coincident catches or
catch rates of mackerel. An analysis of commercial catch
data and environmental variables might be revealing since,
typically, catches are larger and more frequent in these
operations. Additional field sampling of the short-termand
long-term distributional changes in the stock with accom-
panying environmental data would be useful as would
detailed records of recreational catches by state. A tagging
study would not only be useful in determining the propor-
tion of northern versus southern components in the stock,
but would also help detail fish movements and changes in

distribution. Remote sensing technology may also be
useful for studying this problem and would be important in
providing short-term forecasts of probable changes in
distributions of mackerel on a real-time basis.

ACKNOWLEDGMENTS

The authors wish to thank M. Ingham, R. Schlitz, and
G. Shepherd of the NEFSC, and T. Hoff of the MAFMC, for
their assistance in determining the course of this study. We
also want to express our thanks to all the people who have
collected the bottom trawl survey, environmental, and
recreational catch data over the years, thereby making this
effort possible. Special thanks are due to T. Holzwarth and
M. Taylor for helping with the figures.

REFERENCES CITED

Anderson, E.D. 1981. Status of the Northwest Atlantic
mackerel stock - 1981. [Nat. Mar. Fish. Serv., Northe.
Fish. Ctr.,] Woods Hole Lab. Ref. Doc. No. 81-38. 38
Pp.

Anderson, E.D., and F.P. Almeida. 1977. Distribution of
Atlantic mackerel in ICNAF Subarea 5 and Statistical
Area 6 based on research vessel spring bottom trawl
surveys, 1968-1976. ICNAF [Int Comm. Northw. Atl.
Fish.] Sel. Pap. 2: 33-44.

Anderson, E.D., and A.J. Paciorkowski. 1980. A review of
the Northwest Atlantic mackerel fishery. Rapp. P.-V.
Reun. Cons. Int. Explor. Mer 177: 175-211.

Azarovitz, TR. 1981. A brief historical review of the
Woods Hole Laboratory trawl survey time series. Can.
Spec. Publ. Fish. Aquat. Sci. 58: 62-67.

Berrien, P. 1982. Species synopses: Atlantic mackerel
(Scomber scombrus). Pages 99-102 in MD. Grosslein
and T.R. Azarovitz, eds. Fish distribution. MESA [Mar.
Ecosyst. Anal. Prog.] N.Y. Bight Atlas Monogr. 15.
New York Sea Grant Institute, Albany, N.Y. 182 pp.

Christensen, D.J.,and WJ. Clifford. 1980. The 1978spring
recreational catch of Atlantic mackerel, Scomber
scombrus, off the Middle Atlantic region. Fish. Bull.,
U.S. 78: 799-805.

Clark, JR. 1967. The 1960salt-waterangling survey. U.S.
Fish Wildl. Serv. Circ. 153. 35 pp.

Colton, JB., and R.B. Stoddard. 1972. Average monthly
sea water temperatures - Nova Scotia to Long Island,
1940-1959. Ser. Atlas Mar. Environ.:Folio21. Ameri-
can Geographical Society, New York.

Devel, D.G. 1973. The 1970 salt-water angling survey.
Nat. Mar. Fish. Serv. Curr. Fish. Stat. No. 6200. 54 pp.

Devel, D.G., and JR. Clark 1968. The 1965 salt-water
angling survey. U.S. Fish Wildl. Serv. Resour. Publ
67. 51 pp.

Grosslein, MD. 1969. Groundfish survey programof BCF
Woods Hole. Comm. Fish. Rev. 31(8-9): 22-35.
Han, G., and T. Niedrauer. 1981. Hydrographic observa-
tions and mixing processes in the New York Bight,

1975-1977. Limnol. Oceanogr. 26: 1126-1141.

Hoy, DL., and GM. Clark. 1967. Atlantic mackerel
fishery, 1804-1965. U.S. Fish Wildl Serv. Fish. Leaf.
603. 9 pp.

Mountain, D.G., and T.J. Holzwarth. 1989. Surface and
bottom temperature distributions for the Northeast
Continental Shelf. NOAA [Nat. Ocean. Atmos. Admin.]
Tech. Mem. NMFS [Nat. Mar. Fish. Serv.]-F/NEC-73.
32 pp.

Murray, T. 1984. Predicting the timing and duration of
Atlantic mackerel migrations in the Middle Adantic
Bight using sea surface temperature. Unpublished
manuscript available from National Marine Fisheries
Service, 166 Water St, Woods Hole, MA 02543-1097.

Murray, T., S. LeDuc, and M. Ingham. 1983. Impact of
climatic factors on early life stages of Atlantic mack-
erel, Scomber scombrus, L.: an application of meteo-
rological data to a fishery problem. J. Climar. Appl.
Meteorol. 22: 57-68.

Olla, BLL., A.J. Bejda, and ALL. Studholme. 1976. Swim-
ming speeds of Atlantic mackerel, Scomber scombrus,
under laboratory conditions: relation to capture by
trawling. ICNAF [Int. Comm. Northw. AtL Fish] Res.
Doc. 76/X0/143. 6 pp.

Overholtz, W.J., and ED. Anderson. 1976. Relationship
between mackerel catches, water temperature, and
vessel velocity during USA spring bottom trawl sur-
veys in SA 5-6. ICNAF [Int. Comm. Northw. AtL
Fish] Res. Doc. 76/X1I/170. 7 pp.

Overholtz, W.J.,andB.L. Parry. 1985. Update of the status
of the Northwest Atlantic mackerel stock for 1985.



inal

BIBLIOGRAPHIC INFORMATION

PB92-160299

Report Nos: NOAA-TM-NMFS-F/NEC-85

Title: Factors Influencing Spring Distribution, Availability, and Recreational
Catch of Atlantic Mackerel ('Scomber scombrus') in the Middle Atlantic and Southern
New England Regions.

Date: Aug 91
Authors: W. J. Overholtz, R. S. Armstrong, D. G. Mountain, and M. Tercerio.

Performing Organization: National Marine Fisheries Service, Woods Hole, MA.
Northeast Fisheries Center.

Type of Report and Period Covered: Technical memo.

Supplementary Notes: See also PB89-151948 and PB99-252172.

NTIS Field/Group Codes: 98F, 57Z
Price: PC AQ3/MF AG1

Availability: Available from the National Technical Information Service,
Springfield, VA. 22161

Number of Pages: 19p

Keywords: *Fisheries, *Sport fishing, Maps, Population dynamics, Fish migration,
Environmental effects, Spring season, “Atlantic mackeral, Scomber scombrus, Catch
statistics, Atlantic Coast (United States).

Abstract: The relationship between the spring distribution of Atlantic mackerel
(Scomber scombrus), environmental factors, and the recreational fishery for
mackerel in the Mid-Atlantic-Southern New England region was investigated. The
Northwest Atlantic stock of Atlantic mackerel is highly migratory, with the
southern spawning contingent showing a pronounced inshore and northward migration
during the spring and early summer, and the northern spawning contingent moving
north into the Gulf of St. Lawrence at this time. Examined were catch distribution
maps constructed from spring research vessel bottom trawl surveys; results
indicated that the center of abundance of the stock shifts toward the south in
years with cool-to-moderate shelf temperatures and shifts northward in warmer
years. Catches of mackerel in the Northeast Fisheries Science Center's spring
bottom trawl surveys are usually at bottom water temperatures of 5 dec C or
greater, mackerel tend to actively avoid cooler water. Recreational catch in the
Mid-Atlantic - Southern New England region is positively, but weakly, correlated
with stocksize, and is probably highly influenced by the thermal regime in the
early spring.



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49. Northeast Fisheries Center Framework for Inshore Research. By Research Planning & Coordination Staff,
Northeast Fisheries Center. July 1987. vi + 44p., 2 figs., 2 tables. NTIS Access. No. PB87-232286/AS.

50. Status of the Fishery Resources Off the Northeastern United States for 1987. By Conservation & Utilization
Division, Northeast Fisheries Center. October 1987. iii + 132 p., 48 figs., 50 tables. NTIS Access. No. PB88-148549.

51. An Annotated List of the Fishes of Massachusetts Bay. By Bruce B. Colletteand KarstenE. Hartel. February 1988.
x+70p., 1 fig. 1 table. NTIS Access. No. PB88-179247/AS.

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Group, Northeast Fisheries Center. March 1988. ix + 83 p., 33 figs., 13 tables. NTIS Access No. PB88-201983/AS.

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Composition. By Anthony Calabrese, Lawrence J. Buckley, and J. Christopher Powell. May 1988. vii + 37p., 10 figs.,
11 tables. NTIS Access. No. PB88-225628/AS.

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Anthony L. Pacheco, ed. July 1988. v + 322 p., 136 figs., 21 tables. NTIS Access. No. PB89-145262/AS.

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August 1988. iii + 20p. NTIS Access. No. PB89-113013/AS.

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February 1987. By W. David Shuford and Larry B. Spear. September 1988. vii +27p., 14 figs., 1 table. NTIS Access.
No. PB89-141311/AS.

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(continued on inside back cover)

- sre


72 75 eB ce

Figure Sa. Surface temperature contours (1°C interval) from a
spring bottom trawl survey conducted by the Northeast
Fisheries Science Center from Cape Hatteras, North
Carolina, to Georges Bank in 1981.

Delaware and New Jersey is generally higher than the other
states. The New York catch is characterized by fish arriving
in early to mid-May, a fairly consistent pattem of annual
catch over the period, and variable CPUE (Table 2). The
Delaware, New Jersey, and the New York fisheries are
apparently more reliable in terms of mackerel being avail-
able to fishermen (Table 2).

Correlations between recreational catch and water
temperature, wind stress, and stock size during the 1979-87
period were used to investigate various hypothesized rela-
tionships. The correlation between recreational catch and
stocksize from this period was positive, but the relationship
was rather weak (F=0.32, not significant), and it was
necessary to drop the 1981 data point from the analysis to
explain this amount of variation (Table 3; Figure 7). Even
though the recreational catch in 1981 was high relative to
stock size, there is probably no good reason for removing
this data point from the model.

A much stronger [r*=0.47, P=0.043 (significant at the
0.05 level of confidence)] relationship was found between
recreational catchand survey inshore temperature for 1979-
87, and there appeared to be no patterning in the residuals
(Table 3; Figure 8). We also correlated recreational catch
and March meridional wind stress for 1979-87. Results
suggested a statistically significant, negative relationship
[F-0.52, P=0.028 (significant at the 0.05 level of confi-
dence)] with independent error terms (Tzble 3; Figure 9).
The correlation and strength of the wind stress model

Figure Sb. Surface temperature contours (1°C interval) from a
spring bottom trawl survey conducted by the Northeast
Fisheries Science Center from Cape Hatteras, North
Carolina, to Georges Bank in 1982.

depended highly on one data point, the 1981 observation
Figure 9).

Several multiple regression models were also fitted to
see if there might be important combinations of indepen-
dent variables that would enhance the simple relationships
suggested by the univariate models. A model relating
recreational catch to stock size and surface-water tempera-
ture for the 1979-87 period was only marginally better than
the model with temperature alone (Table 3). If the 1981 data
point were dropped from the analysis, however, a measur-
able improvement in the model results occurred, but, again,
this isnot justified based onany objective criteria (Table 3).
The overall coefficient of determination increased to 0.84
for this model, but stock size was still the least important of
the two independent variables. A model relating recre-
ational catch to inshore surface temperature and wind stress
for 1979-87 was also fit and proved to be highly significant
[F=0.86, P=0.0028 (significant at the 0.01 level of confi-
dence)] (Table 3). An examination of exror structure
indicated that the residuals from this model were indepen-
dent and unpatterned. The independent variables in this
model alsoappeared to be uncorrelated, andeachaccounted
for a significant amount of the variation in the model fit.

DISCUSSION

‘Temperature is apparently one of the dominant factors
influencing the spring distributionand the rate of northward


Recreational Catch (o00's mt)

° 1 2 3 4 5 6
Stock Size (billions 3+)
Figure 7. Recreational catch versus stock size (in numbers of

fish) for 1979-87 with linear regression line, computed
without the 1981 data point.

temperature of inshore surface water and the factors that
maintain this in the short term. The latge catch that
occurred in 1981 may have resulted froma combination of
relatively warm temperature and wind conditions that
maintained this thermal pattern, even though abundance of
mackerel at this time was rather low.

Analyses from this study also suggest that recreational
catches along the Mid-Auantic coast are only weakly
related to stock size (Table 3). This is somewhat
counterintuitive since it is often assumed that stock sizes
must be maintained at high levels toachieve highcatchrates
with inefficient angling gear. However, since the catch (in
numbers of fish) in any given year is relatively small when
compared to the overall stock size, local variations in fish
availability determine catch even when thestock is very low
(Table 1). In 1981, a year with a large catch relative to
estimated total stock size, the amount removed by the
recreational fishery was only about one percent of the
exploitable stock. In 1987, only about 0.1 percent of the
estimated total stock was removed by the recreational
fishery. This implies that environmental cues and influ-
ences are probably more important in determining the
tTMagnitude of the spring fishery since the catch can be
relatively large even if the exploitable stock is small.

The time series of sport fishery catches from the states
of Virginia and Maryland are not adequate for correlation
analyses. Therefore, we could not perform fine-scale
studies of relationships within these areas to quantify the
local environmental events that may be important at this
time of the year. It is likely, however, that temperature
plays an important role in determining whether mackerel
Move inshore and are available to the fishermen in Virginia
and Maryland. These two areas do not appear to be in the
normal migratory corridor of this species, as evidenced by

a eee
Page 11

10-
= .
E g-
2
°
3
2
g
2
3
o
gS
2
os
2
GS 2-
€

o-- - -

° 2 4 6 8
Surface Temperature (C)

Figure 8. Recreational catch versus average surface temperature
from spring bottom trawl surveys for 1979-87 with
linear regression line.

E gt

2

o |

3

3

-_ 55

$i

3

2 |

e 45

2

s

2 o!

5 2-

3

e | .
od

600 -500 ~100 -300 -200 +100 0 100
March Wind Stress (o00's dynes/cm2)

Figure 9. Recreational catch versus meridional component of
March wind stress for 1979-87 with linear regression.
Tine.

the patterns in the bottom traw] survey distributions and
statistics from the recreational catch surveys. Therefore,
the fish only occasionally show up along shore in quantity
and donot stay long (Figures 3b,c; Table 2). The fishery in
this area can be expected to be highly variable since the
mackerel appear to be heading northward rather quickly at
this time of the year to aggregate for spawning in the area
off New Jersey and New York (Sette 1950).

Our analysis should not be considered definitive, but
more appropriately, suggestive of possible relationships
and causal factors that may be important in determining the
spring distribution and catch of mackerel in the Mid-