A preliminary study of the movements of pelagic estuarine fishes with special reference to bluefish (Pomatomus saltatrix)

1
A preliminary study of the movements of pelagic
estuarine fishes with special reference to
bluefish (Pomatomus saltatrix)
Lauren Rizzo¹, John Manderson², Jeffrey
Pessutti², John Rosendale², Beth Phelan²
¹Smith College, 1 Chapin Way, Northampton, MA
01063 ² NOAA/NMFS/NEFSC, 74 Magruder Rd,
Highlands, NJ 07732
ABSTRACT Bluefish (Pomatomus saltatrix) and
striped bass (Morone saxatilis) are dominant
summer predators in Mid-Atlantic Bight estuaries.
Bluefish and striped bass movements and
reactions to biotic and abiotic gradients were
ultrasonically tracked by a 27-acoustic receiver
array deployed in the Navesink River, New Jersey.
Vemco V9-16L transmitters were surgically
implanted into fish captured and re-released into
the Navesink. Physical and biological habitat
characteristics were measured by 7 Instruments
moored throughout the river recording aspects of
the river, and routine whole-system surveys using
CTDs with a variety of sensors. Data from the
receivers was downloaded on June 26,2006 and July
6, 2006. Preliminary analysis indicates that
bluefish movements are positively correlated with
tidal currents. Fish appear to congregate in the
mouths of smaller creeks, and tended to return to
these locales at the end of upstream or
downstream movements.
Striped bass also moved up and downstream, but in
response to changes in daylight rather than tidal
height or current velocity. While most
individuals moved upstream at night and
downstream by day, others did the reverse.
The receivers were retrieved on June 26, 2006 and
the data analyzed. Data was also downloaded on
June 26 from 7 continuously recording (20 min.
interval) instruments deployed throughout the
system (3 STAR ODI, 3 YSI and 1 RCM-9 see
Fig.1). The instruments measured pressure, water
temperature, salinity, dissolved O2, current
speed and direction, and turbidity. The movements
of the fish were analyzed in space and time and
compared to physical conditions at 500m and
whole-system scale.
RESULTS Bluefish appear to migrate several times
a day, following the direction of the current and
generally stopping at creek mouths where
chlorophyll concentrations are relatively high
(Fig. 2a). Chlorophyll A concentrations were
generally highest in Red Bank Bay, near the
primary freshwater source of the Navesink
(Swimming River).
INTRODUCTION Estuaries provide important summer
nursery and feeding habitats for bluefish and
striped bass during juvenile and adult stages.
Both species are apex predators in estuaries and
important to commercial and recreational
fisheries. Bluefish use coastal waters of the
Western Atlantic as spawning areas (Bigelow,
2002). Striped bass spawn in the oligohaline
regions of estuaries. Bluefish and striped bass
habitats overlap significantly in the summer and
early autumn months (Buckel, 2002) potentially
leading to competition. Diets of the two species
diverge as individuals become larger (Hartman,
1995) and may therefore result in differences in
habitat preferences. Combining acoustic tracking
of striped bass and bluefish with extensive
mapping of pelagic habitat features, we
contrasted habitat preferences of both species at
subhourly to seasonal time scales. Using
telemetry, we examined the relationship between
the movements of fish and local conditions in
each part of the river. The goal of the study is
to combine tracking data with habitat
measurements to model preferred habitat for each
of the tagged species.
McClees Creek
Fig. 5 Movements of striped bass 1459 upstream
at night and downstream during the day over a 5
day period. Yellow and black lines at the top of
the plot indicate day and night, respectively.
a
Red Bank Bay
b
c
Fig.2 Physical features measured throughout the
Navesink River on June 21 hydrographic survey (a)
Chlorophyll A concentrations increase from beige
to green. (b) Surface salinity decrease from
green to violet (c) Surface temperature increases
from blue to red.

• DISCUSSION
• Most bluefish swim upstream during flooding
  currents and downstream on the ebb. A number of
  fish moved upstream from McClees Creek to Red
  Bank Bay where there was often a chlorophyll A
  front where concentrations of prey that feed on
  phytoplankton (e.g. Menhaden and Anchovy) may
  also be high.
• Striped bass moved on a diel cycle. The movements
  of many fish were centered around Red Bank Bay,
  but others used the lower part of the estuaries
  in the vicinity of the Oceanic Bridge.
• By June 29th, only 7 fish had been detected at
  the receiver gating Sandy Hook Bay (2748
  detections). Of these, 5 fish left the study
  area, while 2 returned to the Navesink River.
• Of the 8 bluefish included in the study, only one
  traveled into Sandy Hook Bay, but eventually
  returned to the river.

Most bluefish appear to make tidal migrations
between the Red Bank Bay and McClees Creek,
moving upstream during the flood tide and
downstream during the ebb.
a
b
Fig.3 (a) Total number of detections of 8
bluefish at the receivers in the Navesink River
from June 6-26 (Max detections13,000), (b)
movement of bluefish 2252. Each blue point is a
detection. The black lines above the graph
indicate night/dark time. Meters west describes
how far upstream the fish was detected. The
westernmost station in the river was 8534 m
upstream while McClees Creek is located at 5711
m.
Fig.1 Location of the Navesink River in New
Jersey and of the 27 ultrasonic receivers used in
the tagging experiment. Filled symbols indicate
stations where probes measuring habitat variables
are also moored.
REFERENCES Bigelow, A.F., W.C. Schroeder, B.B.
Colette, G. Klein-MacPhee, and H.B. Bigelow.
2002. Bigelow and
Schroeders Fishes of the Gulf of Maine, 3rd
edition. Smithsonian Institute Press,
Washington, D.C. Buckel, J.A., and K.A. McKown.
2002. Competition between juvenile striped bass
and bluefish resource partitioning and growth
rate. Marine Ecology Progress Series
234191-204. Hartman, K.J., and S.B. Brandt.
1995. Trophic resource partitioning, diets and
growth of sympatric estuarine predators.
Transactions of the American Fisheries Society
124520-537. Mulcahy, D.M. 2003. Surgical
implantation of transmitters into fish.
Institute for Laboratory Animal Research Journal
44295-306. Schreck, C.B., P.B. Moyle, and
American Fisheries Society. Education Section.
1990. Methods for Fish Biology. American
Fisheries Society, Bethesda, MD.
METHODS
We examined the movements (m) of each bluefish
from June 21-26. We then binned the data by hour
and calculated the average location of each fish
for each hour. We used these data to calculate
the distance moved upstream or downstream from
the previous hour. These movement patterns were
compared with cycles of daylight, tidal depth and
current direction. Bluefish movements were
significantly correlated (r0.41, pltlt0.001) with
westward tidal current velocity (m/sec) but not
the other variables (Fig. 4).
The Navesink River is a 12km long riverine
estuary in New Jersey. Ultrasonic acoustic
receivers were deployed every 500m throughout
the river as well as at the confluence of the
Navesink and the Shrewsbury and Sandy Hook Bays.
Fish (8 bluefish and 34 striped bass) were caught
from May 5 June 21, 2006 with hook and line and
brought back to the laboratory for surgery. Fish
were surgically tagged with ultrasonic
transmitters (see Schreck, 1990, Mulcahy, 2003
for methods) and external tags and released after
surgery at random locations throughout the river.
Vemco Code Fork Length Release Date Days at Large
2250 330(mm) 6/22 5
2251 275(mm) 6/22 5
2252 310(mm) 6/22 5
2253 318(mm) 6/22 5
2273 295(mm) 6/21 6
2274 282(mm) 6/21 6
2275 285(mm) 6/22 5
1463 278(mm) 6/5 21
ACKNOWLEDGEMENTS I would like to thank the other
CMER interns for helping me to keep my spirits up
this summer, my mentor for deciding that this
would be a good year to stop with the dead fish
babies and for showing me the wonders of pivot
tables, and the folks at Rutgers running the
CMER/RIOS internship project. Thanks to my mom
for allowing me to live in her house for the
summer, even though I frequently came home
smelling of fish. Thanks also to the members of
SSFFS for being especially supportive while I
tried to figure out what I was doing. Background
was composed of images from www.alltackle.com.
(GMT)
Table 1 A table of the 8 released bluefish.
Vemco code refers to the surgically implanted
acoustic transmitter in each fish. Days at Large
is the number of days between release and first
data download
Fig. 4 Average distance moved by bluefish/hour.
Violet represents bluefish movements in meters
west/hour Green, tidal currents (m/sec) and
blue is tidal depth (meters). Black and yellow
bar above the x-axis indicate night and day,
respectively. Unpooled bluefish movements were
significantly correlated with tidal current
velocity but not the other variables.