Seasonal Use of a New England Estuary by
Foraging Contingents of Migratory Striped Bass
SARAH M. PAUTZKE1
Massachusetts Cooperative Fish and Wildlife Research Unit, Department of Natural Resources Conservation,
and School of Marine Sciences, University of Massachusetts, Amherst, Massachusetts 01003, USA
MARTHA E. MATHER*
U.S. Geological Survey, Massachusetts Cooperative Fish and Wildlife Research Unit, and
Department of Natural Resources Conservation and School of Marine Sciences, University of Massachusetts,
Amherst, Massachusetts 01003, USA
JOHN T. FINN
Department of Natural Resources Conservation and School of Marine Sciences, University of Massachusetts,
Amherst, Massachusetts 01003, USA
LINDA A. DEEGAN
The Ecosystems Center, Marine Biological Laboratory, Woods Hole, Massachusetts 02543, USA
ROBERT M. MUTH
Department of Natural Resources Conservation and School of Marine Sciences, University of Massachusetts,
Amherst, Massachusetts 01003, USA
Abstract.—Using acoustic telemetry on migratory striped bass Morone saxatilis in Plum Island Estuary
(PIE), Massachusetts, we found that striped bass (335–634 mm total length) tagged in the spring and summer
of 2005 (n¼ 14) and 2006 (n¼ 46) stayed in the estuary for an average of 66.0 d in 2005 and 72.2 d in 2006.
Striped bass spent the most time in two specific reaches: middle Plum Island Sound and lower Rowley River.
In both years, three different use-groups of striped bass were observed in PIE. Short-term visitors (n ¼ 24)
stayed in the estuary only briefly (range¼ 5–20 d). Two groups of seasonal residents stayed for more than 30
d, either in the Rowley River (n¼14) or in Plum Island Sound (n¼22). Within PIE, the two seasonal-resident
use-groups may be foraging contingents that learn how to feed efficiently in specific parts of the estuary.
These distinct within-estuary use patterns could have different implications for striped bass condition and prey
impact.
The location, timing, and movements of Atlantic
coast stocks of striped bass Morone saxatilis can affect
their survival, growth, and impact on local prey. The
coastal migratory stock spawns primarily in the
Chesapeake Bay, Delaware River, or Hudson River
(Collette and Klein-MacPhee 2002); many of these
migrants then move along the coast in the spring and
return in the fall (Clark 1968; Dorazio et al. 1994).
Little is known about how these migrants use New
England estuaries in summer, even though many
striped bass are caught there during their seasonal
foraging migration (Berggren and Lieberman 1978;
Fabrizio 1987a, 1987b; Mather et al. 2009). Here, we
examined migration timing, duration of estuary use,
within-estuary distribution, and individual striped bass
behavior in Plum Island Estuary (PIE) in northeastern
Massachusetts.
Substantial gaps exist in our understanding of how
individual migratory striped bass use estuaries in
summer and whether adult distribution varies across
coastal systems. Older studies, which are based mostly
on single recaptures of externally tagged fish, describe
general coastal movements. These studies show that
after the spawning season, Atlantic striped bass migrate
north along the coast before returning south in the fall
to the area where they overwinter (Boreman and Lewis
1987; Waldman et al. 1990). Recent acoustic telemetry
studies of other coastal populations (Haeseker et al.
1996; Carmichael et al. 1998; Bjorgo et al. 2000)
provide multiple detection data on individual striped
bass that inhabit coastal systems. These fish, however,
do not typically move long distances north–south along
* Corresponding author: mather@nrc.umass.edu
1 Present address: Western Pacific Fishery Management
Council, Honolulu, Hawaii 96813, USA
Received December 15, 2008; accepted September 12, 2009
Published online December 10, 2009
257
Transactions of the American Fisheries Society 139:257–269, 2010
 Copyright by the American Fisheries Society 2009
DOI: 10.1577/T08-222.1
[Article]
the coast. Recent acoustic tagging studies within the
natal Hudson River (New York; Wingate and Secor
2007) and the nonnatal Mullica River–Great Bay (New
Jersey; Able and Grothues 2007; Ng et al. 2007;
Grothues et al. 2009) estuaries provide the first
example of multiple-detection movement data for
individual striped bass coastal migrants.
For several reasons, migratory striped bass may be
distributed differently in PIE than in other estuaries.
Like many temperate estuaries, PIE experiences
distinct changes in seasonal productivity. Because
PIE is located in the middle of the range through
which striped bass migrate, is moderately large, and
has constricted connections to the ocean, migratory
striped bass may experience different conditions in this
system than in other estuaries they encounter. To
quantify where striped bass tagged in PIE spend their
time during their summer foraging migration, we used
acoustic telemetry on 60 adult migratory striped bass
over the span of 2 years. First, we assessed how long
and in what season individual striped bass used PIE.
Second, we determined whether striped bass spent
equal time in all reaches of the estuary or whether they
favored specific locations. Third, we examined whether
distribution within PIE changed with season. Fourth,
we identified whether individual striped bass belonged
to distinct behavioral groups that had different
movement patterns. Finally, we integrated our results
with recent telemetry studies on coastal migratory
striped bass to recommend standardized metrics for
future across-system comparisons.
Study Area
Plum Island Estuary (Figure 1A) is the largest salt-
marsh-dominated estuary in New England. This coastal
plain, bar-built estuary has extensive marshes and is
composed of three freshwater rivers (Parker, Rowley,
and Ipswich rivers), one tidal river that serves as a
connection to the ocean (Plum Island River), multiple
tidal creeks (TCs), and a large embayment—Plum
Island Sound (Figure 1B). This ecosystem is vertically
well mixed and has a large semidiurnal tidal range (2.9
m) with low freshwater input (Deegan and Garritt
1997; Vallino et al. 2005). The water body area of the
entire estuary ranges from 12.8 km2 (low tide) to 20.0
km2 (high tide), with extensive areas of nonvegetated
tidal flats exposed at low tide.
To acoustically track striped bass, we divided PIE
into two areas: Plum Island Sound, the wide, open area
that is closest to the ocean (length ¼ 8 km); and the
Rowley River (RR), a narrower area with a well-
defined channel that is fed by numerous TCs (length¼
7.6 km). Each of these two areas is further divided into
three reaches. Except for the TCs, all reaches had a
similar length, although reach areas were generally
larger in the sound than in the river (Table 1; Figure
1B). Lower Plum Island Sound, the southernmost reach
within the Plum Island Sound area, is deep and
relatively wide and has hard substrates. Lower Plum
Island Sound includes both the primary southern
connection with the ocean and the mouth of the
Ipswich River. The second reach within the Plum
Island Sound area (middle Plum Island Sound) is
shallower and wide and also has hard substrates.
Middle Plum Island Sound includes both the conflu-
ence with the RR and Middle Ground Island, a tidally
influenced island with a salt-marsh landscape. The
third reach (upper Plum Island Sound) is deep, is wide
in places, and contains varied substrates. This northern
reach includes the confluence with the deeper Parker
River as well as a connection to the Atlantic Ocean via
the Plum Island River.
The first reach within the RR area (lower RR) is
moderately deep and narrow and has a combination of
hard and soft substrates (Table 1; Figure 1B). The
lower RR reach includes the confluences of numerous,
small, unnamed TCs; is adjacent to Plum Island Sound;
and includes the mouth of the RR. The second reach in
the RR area (upper RR) is shallower, narrower, and
characterized by muddy substrates. The last reach
within the RR (RR TCs) is composed of two
unconnected, named TCs (West and Clubhead creeks)
that are very shallow and narrow and have soft
sediments. The width and depth of all three RR reaches
vary greatly with tidal stage.
Methods
Tagging.—We used VEMCO V13-1H-R256 coded
hydroacoustic tags. Tags had a frequency of 69 kHz
and a ping rate of 20–90 s in 2005 and 40–120 s in
2006. The average tag life was 100 d in 2005 and 275 d
in 2006. The weight of the acoustic tags (6.6 g in
water) was less than 1.8% of the mass of the lightest
tagged striped bass (368 g) and less than 0.8% of the
mean mass of all tagged fish (789 g). Striped bass were
caught via daytime hook-and-line fishing on an ebb
tide in the middle Plum Island Sound and lower RR
reaches. In 2005, 14 striped bass (mean total length
[TL] ¼ 418.9 mm; SE ¼ 15.2 mm; range ¼ 335–510
mm) were caught and tagged in three batches from
mid-July through late August (Figure 2). In 2006, 46
fish (mean TL ¼ 433.7 mm; SE ¼ 7.6 mm; range ¼
380–634 mm) were tagged in two batches (May 27–29
and July 6–7). In 2006, we specifically targeted the
400–500-mm size-class, which was the most common
size in PIE. Based on a size-at-age key for fish caught
in Massachusetts waters, these striped bass were 2–6
years old (mostly 3–5 years old; G. Nelson, personal
258 PAUTZKE ET AL.
communication). The spawning origin of these fish is
unknown.
After capture, fish were held in a large, continually
aerated holding tank (378.5 L; 1.303 0.793 0.64 m).
Using clove oil as the anesthetic (1.5 lL of clove oil/L
of water; mean application time ¼ 7.8 min, SE ¼ 1.6
min; Ferry 2003; Cooke et al. 2004), fish were first
weighed (g) and measured (TL, mm). Tags were then
surgically implanted (Bridger and Booth 2003) using a
sterile scalpel to make a small, 2–3-cm-long incision 2
cm above the ventral midline and approximately 1.5
cm behind the pelvic fin. Through this opening, we
FIGURE 1.—(A) Location of Plum Island Estuary (PIE) in northeastern Massachusetts within the northern portion of the
migratory range of coastal striped bass. Also shown are telemetry arrays in Long Island Sound and Delaware River Estuary,
where our tagged striped bass were detected (H. Brundage, D. Fox, and T. Savoy, personal communication). The Hudson River,
Delaware River, and Chesapeake Bay (three important spawning locations) are indicated with asterisks. (B) The PIE was divided
into two study areas that each contained three reaches: the Rowley River (RR) area (upper RR, lower RR, and tidal creek [TC]
reaches) and the Plum Island Sound (PIS) area (upper, middle, and lower PIS reaches). Dots represent receiver sites used in both
2005 and 2006; stars represent sites that were used only in 2005; and triangles indicate sites that were used only in 2006.
Measurements of each reach are shown in Table 1.
TABLE 1.—Physical attributes of two study areas and six reaches used to quantify within-estuary distribution of migratory
striped bass in Plum Island Estuary, Massachusetts. Shown are area name, reach name, length, area, average depth (midtide),
average width (midtide), substrate, and geographic orientation. All locations are shown in Figure 1.
Area name Reach name
Length
(km)
Area
(km2)
Average
depth (m)
Average
width (km) Substrate
Geographic
orientation
Plum Island Sound (PIS) Lower PIS 2.4 1.97 4.7 0.73 Rock, sand Southern
Middle PIS 3.0 3.96 1.8 1.51 Sand, shellfish beds Middle
Upper PIS 2.6 2.91 5.7 0.5 Sand, mud, mussel beds Northern
Rowley River (RR) Lower RR 2.3 0.52 3.0 0.17 Sand, mud, shellfish beds Downstream
Upper RR 3.4 0.19 2.5 0.042 Mud Upstream
Tidal creeksa 1.9 0.06 1.0 0.03 Mud North of RR main stem
a West and Clubhead creeks.
FORAGING CONTINGENTS OF STRIPED BASS 259
inserted the tag into the peritoneal cavity and closed the
incision with Monocryl dissolvable sutures using a
cutting needle. Equipment and tags were sterilized with
Betadine (Szedlmayer and Schroepfer 2005). To reduce
stress during surgery, the gills and external body
surface were irrigated at all times with estuary water
and the measuring board was kept moist. After tagging,
each striped bass was placed in a cylindrical recovery
tank (113 L; 0.6-m diameter3 0.6-m depth) filled with
ambient estuary water until the fish swam upright
(mean ¼ 8.3 min; SE ¼ 1.2 min). The entire tagging
process took, on average, 11.0 min (SE ¼ 1.0 min).
During the three tagging sessions in 2005, fish were
tagged 4.5 km upstream of the RR mouth, held
overnight to assess posttagging mortality, and then
released on the morning ebb tide. In 2006, fish were
tagged where they were caught, given a dose of
injectable Liquamycin antibiotic (0.1 mg/kg of fish;
Pfizer, Inc., New York, New York), and released
immediately after tagging.
Control experiments.—We used several methods to
assess whether striped bass survived tagging. First, in
2005, we held tagged striped bass in net-pens (0.75-m
diameter 3 1-m height) for 12–15 h after tagging.
Second, in 2006, we held three pairs of tagged and
untagged fish (mean TL ¼ 451 mm; SE ¼ 11 mm) in
separate cylindrical holding pens (1.2-m diameter 3
1.2-m depth) in the RR for 6 d. To further assess
possible mortality related to tagging, we evaluated
three additional responses: (1) the minimum number of
days that tagged fish were present in PIE, (2) whether
fish tagged in 2005 were detected again in PIE in 2006,
and (3) whether tagged fish were detected in other
telemetry arrays along the coast. We assumed that if
fish were detected and moving for months, they were
not adversely affected by tagging.
Receivers.—We placed receivers throughout the six
reaches within the two areas of PIE to provide
extensive coverage with minimal overlap. We de-
ployed 18 VEMCO VR20 receivers in 2005 and 17
VR20 or VR1 receivers in 2006 (Figure 1B). The
VR20s (2005: n ¼ 18; 2006: n ¼ 9) were anchored to
the bottom; the VR1s (2006: n¼ 8) were suspended 1
m below the water surface. All receivers were moored
such that the hydrophone pointed up. In 2005, receivers
were deployed from July 16 to November 18 and were
able to detect fish for a maximum of 125 d. In 2006,
receivers were deployed from May 25 to November 18
and were able to detect fish for a maximum of 177 d.
Receivers were removed in fall (mid-November), 2
FIGURE 2.—Dates when migratory striped bass were tagged and detected in Plum Island Estuary (PIE), Massachusetts, during
2005 (top of figure) and 2006 (bottom of figure). Dates along the top indicate the beginning of each week of data collection. Each
horizontal line represents 1 of 60 fish. Filled cells represent days when fish were detected in PIE. Horizontal patterns indicate
variations in consecutive and nonconsecutive days of detection in PIE. Not all fish were detected on the day of tagging.
260 PAUTZKE ET AL.
weeks after the last fish was detected. Although within-
estuary use was the focus of this study, we also
identified the receiver at which each fish was last
detected and we examined whether tagged fish passed
receivers sequentially as they exited the study area.
We assessed the site-specific range of each receiver
by moving a tag away from each fixed receiver at high
and low tides. By inputting times of tag detection and
Global Positioning System tracks into ArcGIS, we
created starburst plots of receiver ranges at low and
high tides. Based on this, we constructed polygons in
ArcView to quantify the areas that each receiver heard
at high, low, and average tides. The mean receiver
range across all tides was 0.08 km2 (SE ¼ 0.02 km2),
with differences related primarily to local bottom
topography.
Each receiver in the array recorded the tag code,
detection date, and detection time of each fish within
its detection range. Because the thousands of detections
for each fish at each receiver were not independent, we
aggregated these data into the amount of time (h) each
fish spent at each receiver. We termed this variable
‘‘duration’’ and calculated it by totaling the time
between the first observation and last observation at a
receiver for observations 15 min apart or less. This
eliminated temporally correlated detection data at any
single receiver. Duration data were divided by range
size so that data from all receivers represented a
standardized area. Occasionally, receivers did not
detect fish because of dead batteries. For this reason,
data were further standardized temporally so that all
receiver data represented a common time period each
year.
Analyses.—Prior to statistical analyses, we ensured
that fish passed each functional receiver in sequence
and discarded all single-hit data (Clements et al. 2005).
In 2005, to compensate for the release of striped bass 4
km from their catch site, data for the first 4 d
posttagging were not used. Duration data were
combined for all receivers within each of the six
reaches to reduce the number of zeros in the data set.
Coverage in each reach was calculated by summing the
standardized ranges of all receivers within a reach. To
determine whether striped bass resided in PIE season-
ally or were just passing through, we examined
residence time or how many total days (not necessarily
consecutive) that each fish was detected in PIE by
subtracting the tagging date from the date the fish was
last detected in PIE. Polythetic agglomerative hierar-
chical clustering on untransformed data was used with
Ward’s linkage to determine whether different groups
of fish were using PIE for different amounts of time
(e.g., short-term visitors versus seasonal residents).
Ward’s linkage minimizes the between-cluster sum of
squares divided by the total sum of squares, which is
referred to as the semipartial R2 (Legendre and
Legendre 1998). For the seasonal resident group,
we used a one-sample Kolmogorov–Smirnov (K–S)
goodness-of-fit test (Zar 1984) to compare observed
data (time spent in each reach) with the distribution that
would be expected if striped bass used each estuary
location equally (i.e., detected one-sixth of their time in
each reach). To assess whether all individual fish
behaved similarly or whether there were different
groups of seasonal residents, we ran a second
agglomerative hierarchical cluster analysis (Ward’s
linkage) on the amount of time fish were detected in
both the Plum Island Sound and RR areas. We used a
two-population K–S test and a multivariate analysis of
variance (MANOVA) to test whether (1) all fish or (2)
groups of seasonal residents differed in their use of the
six estuary reaches. We then evaluated potential
reasons for differences among use-group distributions,
such as tagging date, departure date, and fish size.
Finally, we examined whether striped bass distribu-
tion across reaches changed by season using a two-
population K–S test and a repeated-measures (RM)
analysis of variance (ANOVA; Sokal and Rohlf 1995;
Quinn and Keough 2002). Spring was defined as May
and June, summer was defined as July and August, and
fall was defined as September and October based on
general shifts in water temperatures and day length. In
all analyses, the experimental unit was the fish (White
and Garrott 1990; Rogers and White 2007). For two
responses (residence time and within-estuary distribu-
tion), we show data for 2005 and 2006. For four
analyses (the two cluster analyses, within-estuary
distribution of foraging contingents, and seasonal
differences), we only show data for striped bass tagged
in 2006.
Results
Survival
Tagged striped bass survived and continued to move
around the estuary and along the coast. In 2005, the 14
striped bass held overnight were alive and healthy at
release (;12–15 h posttagging). The three pairs of
tagged and untagged fish that were held for 6 d in 2006
survived similarly (100%). For these caged fish, no
evidence of tagging stress was observed. All 60 striped
bass tagged in both years were detected in PIE for a
minimum of 6 d after tagging (Figure 2). In the year of
tagging, striped bass remained in PIE from 6 to 96 d in
2005 and from 6 to 122 d in 2006. Nine of the 14
striped bass tagged in 2005 were detected in PIE again
in 2006, at least 215 d after tagging. Finally, 36 of the
60 striped bass that we tagged, including some detected
for only a few days in PIE, were detected in other
FORAGING CONTINGENTS OF STRIPED BASS 261
arrays along the Atlantic coast (i.e., Long Island Sound,
Delaware Bay Estuary; Figure 1A) during their
southern migration, 90–470 d after tagging (H.
Brundage, Environmental Research and Consulting,
Inc., personal communication; D. Fox, Delaware State
University, personal communication; T. Savoy, Con-
necticut Department of Environmental Protection,
personal communication). Thus, in both 2005 and
2006, all fish survived the control experiments. In
addition, all tagged fish (1) were detected in PIE for an
extensive period during the tagging year, (2) returned
to PIE the year after tagging, or (3) were detected
elsewhere along the coast during the winter after
tagging.
Short-Term Visitors versus Seasonal Residents
Some fish remained in PIE for only a short time,
while others were seasonal residents. Coastal migratory
striped bass tagged and released in PIE stayed an
average of 66.0 d in 2005 (SE ¼ 7.6 d) and 72.2 d in
2006 (SE¼ 6.2 d). A cluster analysis of total days for
which fish tagged in 2006 resided in PIE separated fish
into two groups: those that stayed more than 30 d
within PIE, and those with a residence time less than 30
d (Figure 3A). Of the 14 fish tagged in 2005, 50%
stayed within PIE for more than 30 d. In 2006, 29 of 46
striped bass (63%) stayed within PIE for more than 30
d (Figure 3B). All striped bass exited the study area by
October 31 in each year (Figure 2). We refer to fish that
stayed more than 30 d as ‘‘seasonal residents’’ and
those fish that stayed less than 30 d as ‘‘short-term
visitors.’’ Relative to connectivity of movements, 41 of
46 fish in 2006 left PIE via the series of receivers that
gated the estuary. Of these, all but one fish exited via
the southern entrance to Plum Island Sound. Of the
short-term visitors (n ¼ 17), all but one were last
detected at one of the three southernmost receivers.
Striped Bass Distribution within Plum Island Estuary
Striped bass were not evenly distributed across the
six PIE reaches (K–S test and MANOVA on reaches:
2005, not significant; 2006, P , 0.0001). Instead,
tagged striped bass spent the most time in the lower RR
and middle Plum Island Sound reaches in both years
(Figure 4). Possibly because of a small sample size in
2005, distributional patterns were only statistically
significant in 2006. For striped bass that stayed in PIE
more than 30 d, a cluster analysis identified two
distinct groups of seasonal residents (Plum Island
Sound versus RR use-groups; Figure 5A). These
seasonal residents differed in the duration of detection
in the Plum Island Sound area versus the RR area
(Figure 5B). The RR use-group and the Plum Island
Sound use-group were unevenly distributed across the
six reaches (MANOVA: 2006 only, P , 0.0001). One
use-group (RR seasonal residents) spent the most time
in the lower RR reach (Figure 6A). A second use-group
(Plum Island Sound seasonal residents) spent the most
time in the middle Plum Island Sound reach (Figure
6B). The third use-group (short-term visitors; ,30 d in
PIE) roved throughout the entire estuary—albeit only
briefly—prior to exiting the estuary (Figure 6C). We
do not know why fish formed these three use-groups;
however, we know it was not due to differences in date
of capture, date of fish departure, or fish size. Fish in
all three use-groups were caught and tagged in all time
periods; individuals in all three use-groups left PIE in
all time periods (Pautzke 2008). Furthermore, striped
bass in all three use-groups were of similar size (K–S
test: 2005, P¼ 0.53; 2006, P¼ 0.31).
Seasonal Distribution
The length of time spent by the three use-groups in
each location varied statistically across season for all
reaches (RM ANOVA: P  0.05) except lower Plum
Island Sound. In all three seasons (spring, summer, and
fall), the Plum Island Sound use-group used the three
Plum Island Sound reaches more than the other two
use-groups (Figure 7A–C). Their use of upper Plum
Island Sound peaked in spring (Figure 7C), and their
use of middle Plum Island Sound peaked in summer
(Figure 7B). Compared with the other two use-groups,
the RR use-group spent the most time in the RR
reaches in all three seasons (Figure 7D–E). Use of the
lower RR reach by the RR use-group peaked in
summer, when they used this reach approximately 96%
of the time (Figure 7D). Time spent in the upper RR
reach by the RR use-group was highest in spring (they
used this reach 39% of the time; Figure 7E). The RR
fish used the named TCs less than other locations and
ceased this limited use altogether in the fall.
Discussion
Using acoustic telemetry, our study has expanded
what is known about habitat use and movements of
migratory striped bass in estuaries. Specifically, our
results showed that (1) some migratory striped bass
stayed in the tagging estuary for a prolonged period,
whereas others passed quickly through this estuary; (2)
striped bass distribution within PIE was nonrandom;
(3) these patterns of distribution changed seasonally;
and (4) different use-groups may represent foraging
contingents. Much is still unresolved about how striped
bass use the gradient of estuarine systems along the
Atlantic coast. Viewed together, the existing acoustic
telemetry studies on coastal striped bass (Able and
Grothues 2007; Ng et al. 2007; Wingate and Secor
2007; Grothues et al. 2009) and the present study
262 PAUTZKE ET AL.
provide new insights about the complex movements of
these long-distance migrants along the coast and within
estuaries. If researchers adopt common summary
metrics for identifying seasonal timing of residency
(e.g., total days, consecutive days, days by season),
detection time, within-system distribution (e.g., indi-
viduals, catch per unit effort), abiotic and biotic
structure of the estuary, and behaviors of individual
FIGURE 3.—Identification of short-term visitors and seasonal residents in Plum Island Estuary (PIE), Massachusetts, among
migratory striped bass tagged during 2006: (A) results of a cluster analysis based on residence time (difference between the date
of tagging and the date of final detection in PIE), showing fish that stayed in PIE for more than 30 d (i.e., seasonal residents;
above bold horizontal line) and fish that stayed in PIE for less than 30 d (i.e., short-term visitors; below the bold horizontal line).
Clusters are separated based on semipartial R2. Fish are identified by tag numbers. (B) Distribution of short-term visitors (,30 d)
and seasonal residents (.30 d) based on residence time in PIE is presented. The dotted vertical line separates the two clusters.
FORAGING CONTINGENTS OF STRIPED BASS 263
fish, future comparative coastal studies could provide
useful scientific insights for understanding and man-
aging striped bass and other migratory fish.
Although we do not know the natal origin of our
tagged striped bass, four lines of evidence suggest that
the fish we tagged were not permanent residents of
PIE. First, even though some spawning occurs in
striped bass populations in many estuaries along the
Atlantic coast, historically Chesapeake Bay and the
Hudson River have been the primary contributors to
the Atlantic coast striped bass fishery. Second, striped
bass are seasonally abundant in Massachusetts as few
fish are caught in late fall, winter, or early spring and
many fish are caught in summer (Mather et al. 2009).
Third, in a prior study using anchor tags, most striped
bass tagged in Massachusetts during summer were
caught south of the tagging location in the fall and
winter, the time of the southern migration (Mather et al.
2009). Finally, 36 of the 60 fish we acoustically tagged
were detected by southern arrays (Long Island Sound
and Delaware Bay Estuary) in the fall and winter,
coinciding with the time of southward migration (H.
Brundage, D. Fox, and T. Savoy, personal communi-
cation).
Duration of Within-Estuary Residence
Through the summers of 2005 and 2006, many of
our tagged migratory striped bass stayed in PIE for a
prolonged period (i.e., an average of 66.0–72.2 d
across years). Previous research has established that
striped bass reside seasonally in other Atlantic coast
estuaries, but the number of fish, detections, and timing
vary with methodology, migratory status, estuary
characteristics, season of detections, and how the data
are reported. Because external tags are recaptured very
few times, early tag–recapture studies (Clark 1968;
Waldman et al. 1990; Dorazio et al. 1994) provide few
insights into how long individuals reside in specific
estuaries. Various telemetry studies have elucidated
estuary use by migratory striped bass. In the Hudson
River, resident contingent striped bass remained in the
freshwater tidal river for an average of 172 d (Wingate
and Secor 2007). In the nonnatal Mullica River–Great
Bay Estuary, migratory striped bass stayed in the
FIGURE 4.—Mean time (h) spent in six reaches of the Plum Island Estuary (PIE), Massachusetts, by striped bass tagged during
(A) 2005 (n¼ 14 fish) and (B) 2006 (n¼ 46 fish); three reaches were within the Plum Island Sound (PIS) area (lower, middle,
and upper PIS reaches), and three reaches were within the Rowley River (RR) area (upper RR, lower RR, and RR tidal creek
reaches). Durations represent the hours fish were detected per standardized area and time of receiver coverage within each reach.
Vertical dotted line separates data for the PIS and RR areas.
264 PAUTZKE ET AL.
FIGURE 5.—Identification of two use-groups (foraging contingents) among striped bass tagged during 2006 that stayed in Plum
Island Estuary (PIE), Massachusetts, for more than 30 d (seasonal residents; identified in Figure 3): (A) results of a cluster
analysis indicating use-groups for the Plum Island Sound (PIS) and Rowley River (RR) areas based on the hours of fish detection
at receivers within those areas. Clusters are separated based on semipartial R2. Fish are identified by tag numbers. (B) Duration of
time (h) spent in the PIS and RR areas is presented (black dots¼ PIS use-group; gray inverted triangles¼ RR use-group).
FORAGING CONTINGENTS OF STRIPED BASS 265
estuary for an average of 20.0–43.5 d/year, primarily in
the spring and fall (Able and Grothues 2007), a pattern
consistent with temporary use of the nonnatal system
by migratory striped bass. However, mobile telemetry
also revealed that some individual striped bass stayed
in this same estuary for an extended period (Ng et al.
2007). Thus, although the number of days and season
of detection vary across locations, there is consistency
across studies in that estuaries provide either a
destination or a stopover during migration.
Patterns of Within-Estuary Distribution
The striped bass we tagged were distributed in a
heterogeneous pattern within PIE. Although we do not
know why striped bass disproportionately used the
lower RR and middle Plum Island Sound reaches, their
distribution was not related solely to reach size or
length (Pautzke 2008). The lower RR area included
mouths to numerous TCs and a complex bottom
structure. The middle Plum Island Sound area included
heterogeneous habitat as well as a large, tidally
exposed island (Middle Ground Island). Consequently,
the lower RR and middle Plum Island Sound reaches
could have been attractive to feeding striped bass
because of estuarine bathymetry, water movement,
temperature, or prey distribution.
Results of other acoustic research on migratory
striped bass (Able and Grothues 2007; Ng et al. 2007;
Wingate and Secor 2007) also indicate that striped bass
are clustered in specific locations, although patterns
vary across estuaries. Across estuaries, the distribution
of adult striped bass is influenced by a suite of abiotic
and biotic factors. Distribution of striped bass is often
related to temperature, bathymetry, and prey. Within
estuaries, temperature influences nonspawning striped
bass distribution (Coutant and Benson 1990; Bjorgo et
al. 2000; Able and Grothues 2007; Ng et al. 2007;
Wingate and Secor 2007). In many estuaries, striped
bass concentrate near shorelines (Ng et al. 2007),
structures (Haeseker et al. 1996), creek mouths
(Waldman et al. 1990; Tupper and Able 2000), and
other complex habitats (confluences, mussel beds;
Harding and Mann 2003). Striped bass are generalist
feeders that consume forage fish and invertebrates
(Hartman and Brandt 1995; Ferry 2003; Nelson et al.
2003; Walter et al. 2003). Thus, within-estuary
distribution may be related to temperature, habitat, or
prey.
Seasonal Changes in Distribution
Within-estuary distributions changed seasonally.
Striped bass in the Plum Island Sound use-group
utilized several reaches throughout PIE during the
spring but predominately settled into a single reach
during the summer. Rowley River fish spent more than
93% of their time in the RR during spring and summer,
but their use of the river dropped in the fall. This
change in fall distribution was also observed in other
acoustic studies of migratory striped bass (Ng et al.
2007) and may be in preparation for their movement
out of the estuary or in response to changes in
temperature and prey.
Use-Groups (Foraging Contingents)
The three use-groups identified in PIE (i.e., short-
term visitors, RR seasonal residents, and Plum Island
Sound seasonal residents) did not differ consistently by
tagging date, departure date, or fish size. If use-groups
FIGURE 6.—Mean time (h) spent in six reaches of the Plum
Island Estuary, Massachusetts, by three use-groups (foraging
contingents) of striped bass tagged during 2006: (A) Rowley
River (RR) use-group; (B) Plum Island Sound (PIS) use-
group; and (C) short-term visitor use-group. Three reaches
were within the PIS area (lower, middle, and upper PIS
reaches), and three reaches were within the RR area (upper
RR, lower RR, and RR tidal creek reaches). Durations
represent the hours spent per standardized area and time of
receiver coverage within each reach. Vertical dotted line
separates data for the PIS and RR areas.
266 PAUTZKE ET AL.
arrived together, tagged fish might have settled into
similar areas, with the first fish to arrive occupying the
most desirable habitat. Although date of tagging
(known) is not the same as date of arrival (unknown),
date of tagging did not differ across use-groups. We
also hypothesized that based on schooling behavior,
use-groups might stay together. However, individuals
within each use-group did not depart from PIE at the
same time. Furthermore, use-groups did not migrate
along the same route; instead, individuals from all use-
groups were detected in coastal arrays on different days
(T. Savoy, D. Fox, and H. Brundage, personal
communication). We further hypothesized that larger
fish may have used one area, while smaller fish used
another. However, fish in the three use-groups did not
differ in size. Consequently, date of tagging in PIE,
departure date from PIE, and fish size do not explain
how individual fish aggregated into different use-
groups and then used distinct parts of the estuary.
Our use-groups were similar to spawning and
migratory contingents (Clark 1968; Secor et al. 2001)
originally defined by Clark (1968) as a unique group of
striped bass that ‘‘engage in a common pattern of
seasonal migrations between feeding areas, wintering
areas, and spawning areas.’’ Within contingents,
migratory shifts occur, suggesting that these designa-
tions need not remain static over the life of the fish
(Wingate and Secor 2007). Able and Grothues (2007)
FIGURE 7.—Seasonal use of six reaches in Plum Island Estuary (PIE), Massachusetts, by three use-groups (foraging
contingents) of striped bass tagged in 2006: (A) lower Plum Island Sound (PIS) reach; (B) middle PIS reach; (C) upper PIS
reach; (D) lower Rowley River (RR) reach; (E) upper RR reach; and (F) RR tidal creeks reach. Season is shown on the x-axis
(SP¼ spring, SU¼ summer, and FA¼ fall); mean standardized duration (h) after a log
10
transformation is shown on the y-axis.
Use-groups are the PIS use-group (solid circles; present in PIE . 30 d), the RR use-group (open circles; present in PIE . 30 d),
and the short-term visitor (ST) use-group (inverted triangles; present in PIE, 30 d). An asterisk next to the reach name indicates
that repeated-measures ANOVA was statistically significant for that reach (P  0.05).
FORAGING CONTINGENTS OF STRIPED BASS 267
identified four different behaviors of striped bass in the
Mullica River–Great Bay Estuary (resident, seasonal
inlet, seasonal estuary, and seasonal river) but did not
use the term ‘‘contingents’’ to describe these differenc-
es. Although Grothues et al. (2009) suggested that the
striped bass in their study were part of migratory
contingents originating elsewhere, our study of migra-
tory striped bass in PIE is the first to identify individual
striped bass as foraging contingents based on their
distinct use of a nonnatal estuary.
Implications for Migratory Behavior
Coastal migratory striped bass might move season-
ally between their spawning, foraging, and overwin-
tering grounds in two ways. First, striped bass may stop
in various estuaries briefly on their migrations north
and south without staying long in any one location
(Able and Grothues 2007; Grothues et al. 2009). In
fact, this pattern might explain the behavior of some of
our short-term visitors, which moved through PIE in
less than 30 d. Alternatively, striped bass could stay for
an extended period of time in a single estuary, a
behavior that would allow them to ‘‘learn’’ about and
adapt to specific biophysical characteristics of the
estuary (e.g., what prey are available, where and when
prey congregate). These two alternative movement and
foraging patterns can have very different implications
for predators, local prey, and management strategies.
Increasing our knowledge of these within- and across-
estuary movements and residence patterns has the
potential to substantially improve our understanding
and management of migratory striped bass.
Acknowledgments
This research was administered through the Massa-
chusetts Cooperative Fish and Wildlife Research Unit,
an association among the U.S. Geological Survey, the
Department of Natural Resources Conservation (Uni-
versity of Massachusetts), the Massachusetts Division
of Marine Fisheries, the Massachusetts Division of
Fisheries and Wildlife, and the Wildlife Management
Institute. We thank the many people that helped with
fieldwork, and we thank the School of Marine Sciences
(University of Massachusetts) and the Massachusetts
Marine Fisheries Institute. The comments of Steve
Cadrin, Greg Skomal, Thomas Grothues, and three
anonymous reviewers improved the quality of the
manuscript. Joe Smith assisted with the cluster
analysis. Cristina Kennedy assisted with line drawings.
We also thank the following researchers whose
telemetry work in other areas along the Atlantic coast
provided valuable insight into where our striped bass
traveled: Tom Savoy, Dewayne Fox, Hal Brundage,
and Ilene Eberly (Wetlands Institute). Reference to
trade names does not imply endorsement by the U.S.
Government.
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FORAGING CONTINGENTS OF STRIPED BASS 269