ICES Journal of Marine Science, 58: 1286–1298. 2001
doi:10.1006/jmsc.2001.1118, available online at http://www.idealibrary.com on
The influence of tidal streams on the pre-spawning movements of
Atlantic herring, Clupea harengus L., in the St Lawrence estuary
Karine N. Lacoste, Jean Munro, Martin Castonguay,
François J. Saucier, and Jacques A. Gagné
Lacoste, K. N., Munro, J., Castonguay, M., Saucier, F. J., and Gagné, J. A. 2001.
The influence of tidal streams on the pre-spawning movements of Atlantic herring,
Clupea harengus L., in the St Lawrence estuary. – ICES Journal of Marine Science, 58:
1286–1298.
Eight Atlantic herring (Clupea harengus L.) implanted with ultrasonic transmitters
were tracked to determine their movements during the pre-spawning period in the
tidally energetic, upper St Lawrence estuary. Herring released near the south shore
travelled upriver near the shore while herring released near an island where significant
spawning occurs remained in the vicinity of that island. Herring near the shore moved
upriver regardless of the tidal phase while herring close to the island swam actively
against tidal currents during both phases of the tide. Herring near the coast may have
been migrating to an alternate spawning site further upriver while herring near the
island remained in close proximity to the island’s spawning site as a result of their
behaviour. Herring travelling near the coast seemed to take advantage of tidal currents
by swimming with tidal streams when the tide flowed in the migratory direction (flood
tide) and by swimming against them when the tide flowed counter to it (ebb tide).
These fish gained more ground during the flood tide than they lost during the ebb. A
circular statistical analysis of movements-through-water showed that fish were oriented against the flow during the ebb phase. Selective tidal stream transport was not
observed since there was no evidence of vertical migrations associated with tides.
Keywords: herring, tracking, movements over ground, movements through water,
tidal streams, circulation model.
Received 28 August 2000; accepted 30 April 2001; published electronically 21 August
2001.
K. N. Lacoste, J. Munro, M. Castonguay, F. J. Saucier, and J. A. Gagné: Fisheries
and Oceans Canada, Institut Maurice-Lamontagne, C.P. 1000, Mont-Joli, QC,
Canada G5H 3Z4. Current address for K. N. Lacoste: ISMER, Université du Québec
à Rimouski, 310 des Ursulines, Rimouski, QC, Canada G5L 3A1. Correspondence to
J. Munro: e-mail: [email protected]
Introduction
Two populations of Atlantic herring, Clupea harengus
L., migrate annually up the St. Lawrence estuary to
spawn, one in the spring and one in the fall (Greendale
and Powles, 1980; Rivière et al., 1985; Lambert, 1990;
Munro et al., 1998). Migrating spring-spawners are first
caught in March and April along the lower estuary while
the largest catches are landed in May in the upper
estuary, in the area of Rivière du Loup (Greendale and
Powles, 1980; Bérubé and Lambert, 1997). A major
spawning site of the spring-spawning population has
been located in the middle of the upper estuary, at the
southwest tip of |Ile aux Lièvres by Munro et al. (1998)
(Figure 1). As suggested by larval concentrations (Able,
1978; Auger and Powles, 1980), spring-spawners may
also use other sites around the islands distributed along
the southern shore of the estuary, especially in the
1054–3139/01/061286+13 $35.00/0
vicinity of the |Iles Les Pèlerins. The fall-spawning population migrates to the estuary at the end of the summer
towards spawning grounds in the same general area as is
indicated by the capture of newly hatched larvae in
September (Fortier and Gagné, 1990).
An important mechanism used by fish during
migration is selective tidal stream transport. A fish
exhibiting selective tidal stream transport ascends the
water column to drift or swim during the favourable tide
and descends to the bottom where currents are weaker
to hold position during the opposing tide (Arnold, 1974;
Greer Walker et al., 1978; Arnold and Holford, 1995).
Selective tidal stream transport is a migratory mechanism used by plaice (Pleuronectes platessa) (Greer
Walker et al., 1978; Harden Jones et al., 1979; Arnold
and Metcalfe, 1995), sole (Solea solea) (Greer Walker
et al., 1980; Greer Walker and Emerson, 1990), Atlantic
cod (Gadus morhua) (Arnold et al., 1994), American eel
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Influence of tidal streams on pre-spawning Atlantic herring
Quebec
Study Site
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78°
68°
60°
69°33
Figure 1. Area where herring were tracked in the upper St Lawrence estuary during spring and fall 1986 and spring 1987. Depth
contours are in metres.
(Anguilla rostrata) (McCleave and Kleckner, 1982;
McCleave and Wippelhauser, 1987; Parker and
McCleave, 1997), and European eel (A. anguilla)
(Creutzberg, 1959; McCleave and Arnold, 1999) in
various tidal systems. Among fast-swimming pelagic fish
species this behaviour has only been shown in sockeye
salmon (Oncorhynchus nerka) (Levy and Cadenhead,
1995). Castonguay and Gilbert (1995) reported that
Atlantic mackerel (Scomber scombrus) avoid tidal
streams in a direction opposed to migration but could
not find any evidence of associated vertical migrations.
Selective tidal stream transport is energetically
advantageous in areas of strong currents (Weihs, 1978;
Metcalfe et al., 1990). The upper St Lawrence estuary is
such an area (e.g. Canadian Hydrographic Service, 1997;
Saucier and Chassé, 2000) and thus provides an opportunity to examine the hypothesis that herring uses
selective tidal stream transport during their migration to
spawning sites upriver.
In this study, individual herring were equipped
with ultrasonic transmitters and tracked during the
pre-spawning period with three objectives in mind: (1) to
examine the relationships between herring movements
and tidal currents, (2) to define the movements of
herring in the vicinity of spawning grounds, and (3) to
locate the spawning grounds. The first two objectives are
addressed in the present paper while the third one was
dealt with in Munro et al. (1998).
Materials and methods
Study area
This study was conducted in the southern portion of the
upper St Lawrence estuary (Figure 1) in the spring and
fall pre-spawning periods of May and September 1986
and May 1987. The upper St Lawrence estuary is funnel
shaped, from 14 to 24 km wide, with an uneven topography composed of several disconnected channels and
troughs separated by ridges and islands. At its downstream end the upper estuary is split by |Ile aux Lièvres
into two distinct portions. The northern portion has a
deep channel, the North Channel, while the southern
portion is a broad shallow region with two channels, the
Pot-à-l’eau-de-vie and South channels.
Herring were tracked in the area between |Ile aux
Lièvres and the south shore of the upper estuary. The
circulation in this area is characterised by mixed semidiurnal tides with a period of 12.42 h and a range of 2 m
(Godin, 1979; El-Sabh and Murty, 1990; Canadian
Hydrographic Service, 1997). Tidal currents are highly
bi-directional along the |Ile aux Lièvres axis (30T, i.e.
30 true north) and can range up to 2 m s 1 (Canadian
Hydrographic Service, 1997). The water column is well
mixed and contains no internal tides (Muir, 1982).
Tracking
The four fish tracked in 1986 were captured near the
Rivière du Loup wharf (Figure 1). In 1987, three fish
were caught near |Ile aux Lièvres, in close proximity to
the Pot-à-l’eau-de-vie Channel, while a fourth was
caught near the |Iles Les Pèlerins, in the South Channel.
Captures were made using monofilament and braided
nylon gillnets operated from a Boston Whaler. Nets
2.5 m in height by 4.5 m long, with 60-mm stretched
mesh size, were set in water 3–10 m deep, about 1 km
from the shore for periods shorter than 15 minutes.
Individuals were kept on board in a 125-l holding tank
1288
K. N. Lacoste et al.
with a constant flow-through supplied with water
pumped directly from the estuary. Herring were selected
for their large size and the absence of visible bruise
marks. Only those exhibiting normal swimming behaviour were chosen. Fish selected for tracking were
mature, 28–34 cm long. A sample from the other fish
caught at the same time confirmed that they were all in
pre-spawning (stages 5 or 6) or in spawning (stage 7)
condition (according to Courtois et al., 1983). This
strongly suggests that the individuals used for tracking
were of similar maturity stages. Given that only herring
mature enough to be spawners were selected and that
spawning of these fish was observed a few weeks after
the tracking period (Munro et al., 1998), it is assumed
that the tracked individuals were exhibiting typical
pre-spawning behaviour.
Ultrasonic transmitters (Vemco model V2B-2L in
1986 and Vemco model V3P-4 in 1987) used for the
experiments were set to selected frequencies between 65
and 77 kHz to allow the identification of individual fish.
Transmitters were 38 mm long by 8.5 mm in diameter in
1986 and 65 mm long by 16 mm in diameter in 1987.
Only those used in 1987 were depth-sensitive. The ultrasonic signal was detected using a Vemco (model V-10)
directional receiving hydrophone which was rotated to
locate the direction of the maximum signal. The hydrophone was connected to a receiver-decoder-amplifier
(Vemco model VR-60) which allowed signals to be heard
with a pair of headphones. The effective detection range
was found to be approximately 500 m.
In 1986 the transmitters were inserted through the
oesophageal duct and into the stomach, an operation
which took approximately one minute. In 1987 the
larger transmitters were inserted in the abdominal cavity
using a surgical procedure similar to that used by
Bidgood (1980). Each herring was submerged in a
10-l anaesthetic tank containing a Quinaldine solution.
Once the fish started to tilt on its side, it was placed on
a board with its head immersed in water to allow
operculum movement. A 2.5-cm incision was made
along the abdominal wall using a scalpel for the initial
opening and surgical scissors to complete the cut. The
transmitter was then inserted in the front and bottom of
the abdominal cavity. The incision was closed by five
stitches with nylon thread and the surgical suture was
disinfected with an antiseptic solution. Each operation
took roughly three minutes. After surgery the herring
was transferred into a recovery tank to resume normal
posture and activity: this took about ten minutes. It was
kept for another ten minutes before release. The two
protocols were tested in 1986 and 1987 prior to the
tracking period by verifying that fish were exhibiting
normal swimming behaviour after being kept for
24–48 h after insertion. Only fish that responded well to
manipulations were released and tracked. All releases
occurred near capture locations.
Following release the transmitter signal was usually
relocated within a few minutes. During tracking the
signal from the transmitter was monitored continuously
by the hydrophone operator. The ship’s position was
determined with Loran-C while the heading was subsequently calculated from the successive positions. As is
usually the case with this type of study these data were
used as a proxy of herring position. Accuracy of
Loran-C positions was deemed correct and relative error
for the along-estuary position was measured to be 20 m
given a clear Loran-C channel signal propagating in this
direction. Each geographical fish position was converted
to latitude and longitude and plotted onto a map using
a Mercator projection.
The herring positions were recorded whenever a
change in speed or direction was detected. Over-theground speeds were estimated by dividing the distance
travelled by the boat by the time between successive fish
positions. The fish’s direction was transformed and
reported with reference to 30T along the axis of the
estuary. The depth was measured by the boat’s echosounder. The net distance travelled (the straight-line
distance from release point to end of tracking point) and
the gross distance travelled over the ground (the actual
distance travelled by fish) were calculated on the
Mercator plane. Gross speed was obtained by dividing
gross distance travelled over the ground by the duration
of the tracking. For each individual in a given semidiurnal tidal cycle, the net displacement along the axis of
the estuary was obtained by adding the incremental
displacements. The tidal cycle was defined to begin with
the low water as predicted from the nearby ports of
reference from the Tide and Current Tables, Volume 3
(Canadian Hydrographic Service, 1986, 1987). Given the
phase progression of the tide in this area this time
represents the state of the tide near the individuals to
within 15 minutes.
Estimation of water currents
To estimate the time-dependent tidal current velocity at
the positions of the individuals we made use of a
three-dimensional estuarine circulation model of the
St Lawrence estuary by Saucier et al. (1999) and Saucier
and Chassé (2000). This model was used to produce tidal
current charts for navigation in this area (Canadian
Hydrographic Service, 1997). The model has 400-m
resolution in the horizontal and 5-m in the vertical using
a time-step of 60 seconds. It computes water levels, 3D
currents, and density changes driven by the main 15 tidal
constituents that propagate from the Atlantic Ocean and
freshwater from the St Lawrence River and its main
tributaries. Saucier et al. (1999) and Saucier and
Chassé (2000) have shown that the model can reproduce
historical current meter measurements to about 10%
relative error for the semi-diurnal tidal phase and
Influence of tidal streams on pre-spawning Atlantic herring
1289
Table 1. Details on Atlantic herring tracked in the upper St Lawrence estuary. Maturity stage is based on Courtois et al. (1983).
Net distance and direction is the shortest distance and direction between the starting and finishing point of each track. Gross
distance is the actual distance covered by the fish. The direction is shown as relative to 30T because the Estuary is aligned
30–210N.
Initiation of track
Fish
no.
1
2
3
4
5
6
7
8
Length
Maturity
(cm)
Sex
stage
34.0
30.0
30.0
28.0
32.5
33.3
32.0
30.4
F
F
F
M
M
M
M
M
6
6
7
5
5
5
5
5
Date
6 May 86
19 May 86
26 May 86
5 Sept. 86
15 May 87
16 May 87
18 May 87
20 May 87
Movement over ground
Time Tidal Direction
(EDT) stage
(30T)
12:30
12:45
15:55
01:35
12:29
13:52
13:24
16:23
F
E
F
F
F
F
F
F
154.4
341.6
8.6
188.6
188.6
207.6
8.6
141.0
Area
of release
S. shore
S. shore
S. shore
S. shore
|I. Lièvres
|I. Lièvres
|I. Lièvres
S. Channel
Track
Gross
Net
Net
duration distance direction direction
(hh:mm)
(km)
(km)
(30T)
01:15
02:59
27:05
17:56
05:48
06:04
09:02
14:30
3.2
10.4
71.3
60.1
18.8
12.1
17.9
22.1
2.0
8.6
25.4
27.1
8.3
2.1
2.2
7.0
155
338
187
184
196
263
320
101
Tidal stage: F, flood; E, ebb.
amplitude for instruments that were deployed in the area
south of |Ile aux Lièvres (see stations 19 and 41 in
Saucier et al., 1999).
For each fish location and time after low water, the
horizontal water current vectors were extracted from the
model grid using a bilinear interpolation. For tracks or
portions of tracks with missing depth, the current at
mid-depth was used. However, further analyses of the
model results showed that since the water column is well
mixed in this area, the current is quite uniform over the
water column (i.e. highly barotropic) except in the
bottom boundary layer (Saucier and Chassé, 2000).
Data analysis
As previously mentioned, the positions of the tracked
fish were recorded whenever a change in speed or
direction occurred. These raw tracking data were plotted
against tidal phase to examine general patterns.
The speed and direction of fish were thus taken to be
constant between each pair of recorded positions. Fish
positions were subsequently interpolated at 15-minute
intervals, providing a standardised data set for intertidal
and inter-herring comparisons. These standardised
data were analysed using circular statistics methods
(Batschelet, 1981). Over-the-ground velocity vectors
were calculated for each 15-minute interval. The mean
vector and the standard ellipse were calculated over
combined flood tides as well as over combined ebb tides.
The standard ellipse shows the degree of vector dispersion (equivalent to s in univariate statistics) as well as
the directional trend, with the summit of the mean vector
located at the centre of the ellipse. The standard ellipse
is not dependent on the interval between velocity
vectors so that using a different sampling interval would
have yielded the same results (Batschelet, 1981). Because
the sequential 15-minute vectors are not independent of
one another it was not possible to infer statistically about
the significance of the mean vector using the confidence
ellipse. However, if the standard ellipse does not include
the origin then it is very likely that the vectors are not
randomly distributed about the origin, i.e. movements
are oriented (McCleave and Arnold, 1999).
Fish velocity through water was determined as the
difference between the fish velocity over the ground and
the current velocity for each 15-minute interval. The
difference between these two vectors indicates whether
the fish drifted with the tidal flow or swam either with or
against it. The mean vectors and standard ellipses of
velocities through the water were also calculated for the
combined ebb and combined flood portions of the tidal
cycle.
Results
Geographical information on movements
During May and September 1986 and May 1987 a total
of eight herring were tracked in the southeastern area of
the upper St Lawrence estuary (Figure 1; Table 1). The
fish were released in the afternoon during flood tide,
except for one released at night (herring 4) and one
released during ebb tide (herring 2). Track duration
ranged from one hour to over 27 hours and net direction
ranged between 101 to 338 relative to the direction of
the estuary (positive is clockwise with the origin at
30T). The net distance travelled ranged from 2 to
27.1 km. Net distances travelled over the ground
represented less than 45% of the gross distances, with the
exception of 62.5% and 82.7% for herring 1 and 2,
respectively. Differences between net and gross distances
reflect changes in direction and speed of herring.
12:45
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12:30
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Herring 4
(09/05/86)
5
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15
1
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15
10
15
15
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15 20
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10
5
2
Herring 3
(05/26–27/86)
5
0
15:44
5
20
5
2
Herring 1
(05/06/86)
Herring 2
(05/19/86)
10
K. N. Lacoste et al.
10
1290
69°39
69°33
Figure 2. Movements of herring 1, 2, 3, and 4 released along the south shore of the upper St Lawrence estuary. The position of
the fish is plotted on the hour as well as at hourly intervals with circles corresponding to tidal phase ( Flood, Ebb). Times
of start and end of tracking are given (dates as month/day/year). The direction of movement is indicated by arrows. Depth contours
are in metres.
Herring released near-shore in 1986 made progress
upriver by following the coastline in shallow waters
<10 m deep (herring 1, 2, 3, and 4: Figure 2). Herring
tagged near |Ile aux Lièvres in 1987 remained in the
proximity of the island (herring 5, 6, and 7: Figure 3).
Release site and movements of herring 8 were different
from the other herring (Figure 3). Upon release in the
South Channel, farther away from shore than the others,
it travelled towards the south shore and then along the
shore during the last hours of tracking.
Interestingly, after the termination of continuous
tracking of herring 4 due to bad weather, its signal was
picked up again the next day based on a prediction of its
position from its average upriver progress rate. The fish
was relocated at the western end of the |Iles Les Pèlerins
(Figure 1) in shallow waters approximately 5 km upriver
from its last recorded position.
Movements over the ground
Examination of herring tracks according to tidal phase
(Figures 2 and 3) suggests a general fit between the
direction of movement over the ground and the prevailing tidal currents, with the exceptions of the erratic
movements of herring 6 and the shoreward movement of
herring 8.
Stick diagrams of over-the-ground velocities of herring (raw data) also indicate that tidal phase strongly
determined the direction in which herring travelled at
release and afterwards (Figure 4). The direction in which
the fish initially travelled was generally related to tidal
phase (Table 1); most fish released at flood tide travelling upriver while the only fish released at ebb tide
(herring 2) travelled down river. However herring 3 and
7 did not travel in the tidal direction immediately
following their release. This was probably due to the
timing of their release, which occurred within one hour
before or after current reversal (Figure 4). All other
herring were released more than 1.5 h after current
reversal. Throughout the tracking period the agreement
between fish direction and tidal current direction can
also be assessed from the stick diagrams (Figure 4).
However, there appears to be a lag between fish direction and tidal direction for herring 3, 4, and 5. This lag
Influence of tidal streams on pre-spawning Atlantic herring
20
20 5
1 0
1 0
1
18:17
15
52
Il^e
19:56
15
15
2
au
x
50
47°51
2
47°51
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12:29
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15
2
au
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50
Herring 6
(05/16/87)
Li
e´ v
re
s
a´
ot e
u P e-vi
d
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^ le
I aul'E 10
15
52
Herring 5
(05/15/87)
1291
13:52
20
20 5
1 0
1 0
1
5
10
47°49
69°46
a´
ot e
u P e-vi
d
d
^ le
I aul'E 10
15
69°42
Il^e
15
uth
0 1 2 km
69°40
15
2
47°49
2
15
Ile
^
15
69°42
15
0 1 2 km
69°40
69°44
6:53
s
rin
e´ le
sP
47°44
le
0
69°42
0
1
69°40
2 km
5
10
2
5
0
10
0
2
5
5
20
13:24 2015 0
1 0
1
69°44
el
nn
a
Ch
10
0
47°51
15
o
16:23 S
47°46
22:26
10
Herring 8
(05/20–21/87)
15
2
au
x
50
Li
e´ v
re
s
15
52
Herring 7
(05/18/87)
69°46
15
69°44
10
69°42
0 1 2 km
69°40
5
69°44
15
5
69°46
10
0
2
15
0
2
47°49
15
10
Figure 3. Movements of herring 5, 6, 7, and 8 released along the south shore of |Ile aux Lièvres and near the South Channel. Details
as in Figure 2.
could be a result of the fish continuing to swim upriver
after the tidal streams change direction until the tidal
streams exceed its mean swimming speed.
Circular statistics analysis of over-the-ground movements during a flood tide indicates that herring 1, 3, 4,
and 5 were travelling upriver along with tidal currents
(Figure 5). Movements of herring 6, 7, and 8 were more
dispersed during the flood tide since their ellipses include
the origin. The results from herring 8 are somewhat
misleading since it swam towards the coast during the
first flood tide while travelling upriver along the south
shore during the second flood tide (Figure 3). During an
ebb tide analysis of over-the-ground movements shows
that herring tended to travel downstream (Figure 6) as
expected from Figures 2 and 3. However, movements
were defined by a large ellipse indicating that they
were dispersed, especially in the case of herring 3, 4,
and 7.
The net progress-rate calculation revealed a net
upriver movement of the fish during a flood tide while
the opposite prevailed during an ebb tide (Table 2). For
herring 3, 4, and 5, which travelled upriver during flood
tides, the progress rate during a flood tide was greater
than the progress rate in the opposite direction during
an ebb tide, resulting in a net overall upriver displacement ranging from 0.24 to 0.71 m s 1 (Table 2). Upriver
movements during a flood tide also corresponded to
higher gross speed (Table 2) and higher over-the-ground
speed than those during an ebb tide (Table 3).
Movements through the water
Comparisons of current velocities with velocities over
the ground revealed that herring did not passively drift
with the current but rather swam actively (Figures 7 and
8). In fact herring often swam and were oriented against
the flow, this being especially the case during ebb tides.
During flood tides, herring (1, 3, and 4) swimming
near the coast swam more often with the current
while herring (5, 6, and 7) swimming near the island as
well as herring 8 swam more often facing the current
(Figure 7). Herring 1 was oriented and swam upriver
while herring 3 was also oriented but toward the
upriver/centre of the estuary. Herring 6 swam in an
oriented fashion downriver while herring 5 also swam
in an oriented fashion toward the island, across the
1292
K. N. Lacoste et al.
1.2
Herring 1
Herring 5
Herring 2
Herring 6
Herring 3
Herring 7
Herring 4
Herring 8
0.8
0.4
0.0
0.4
0.8
1.2
1.2
0.8
–1
Over the ground velocity (m s )
0.4
0.0
0.4
0.8
1.2
1.2
0.8
0.4
0.0
0.4
0.8
1.2
1.2
0.8
0.4
0.0
0.4
0.8
1.2
12
16
20
24
04
08
Time of day (h)
12
16
20
12
16
20
24
04
Time of day (h)
08
Figure 4. Over-the-ground velocity vectors of herring in relation to tidal cycle. Stick length indicates swimming speed while stick
angle indicates the fish’s heading. The vertical axis follows the longitudinal axis of |Ile aux Lièvres; upriver movements are
represented by sticks oriented towards the bottom of the page. Solid horizontal bars on the x-axis indicate tidal cycle (above axis:
ebb; below axis: flood). Tracking data of each fish are presented in chronological order.
current. Similarly, herring 4 appeared to swim upriver
and herring 7 and 8 appeared to swim downriver, but
changes in direction did occur such that their overall
movements were not oriented as shown by their
ellipses (Figure 7). Through-water mean vector speeds
during flood tides indicate that herring were swimming
at similar speeds (0.448 m s 1, s.e.=0.042, n=7)
regardless of whether they were swimming with
or against the tide (as indicated by direction in
Table 3).
During ebb tides, herring 3, 4, 6, and 7 swam in an
oriented fashion upriver against the tide while herring 2,
1.0
0.5
(1)
1293
(3)
Upstream
1.0
Downstream
Upstream
(4)
Downstream
1.0
0.5
0.5
0.0
0.0
0.5
0.5
Upstream
Downstream
0.0
0.5
1.0
–1
Over the ground speed (m s ) (northwest-southeast)
Influence of tidal streams on pre-spawning Atlantic herring
1.5 1.0 0.5 0.0 0.5
1.0
(5)
1.0
Upstream
1.5 1.0 0.5 0.0 0.5
1.0 0.5 0.0 0.5
Downstream
(6)
Upstream
1.0
Downstream
(7)
Upstream
1.0
Downstream
Upstream
0.5
0.5
0.5
0.5
0.0
0.0
0.0
0.0
0.5
0.5
0.5
0.5
1.0
1.0
1.0
1.0
1.5 1.0 0.5 0.0 0.5
1.0 0.5 0.0 0.5
(8)
1.0 0.5 0.0 0.5 1.0
Downstream
1.0 0.5 0.0 0.5
–1
Over the ground speed (m s ) (northeast-southwest)
(2)
1.0
Upstream
1.0
Downstream
0.5
(3)
Upstream
1.0
Downstream
0.5
(4)
Upstream
Downstream
0.5
0.0
0.0
0.5
0.5
1.0
1.0
0.0
0.5
–1
Over the ground speed (m s ) (northwest-southeast)
Figure 5. Over-the-ground velocities of herring calculated for successive 15-minute intervals during flood tide. The x- and y-axes
correspond to 30T (I|le aux Lièvres axis) and 300T, respectively. The number at the top left of each graph corresponds to the
herring number. The mean vector is in bold. The standard ellipse represents the degree of dispersion of vectors.
0.5 0.0 0.5 1.0
1.0
0.5
(5)
1.0
Upstream
Downstream
0.5
(6)
Upstream
1.0 0.5 0.0 0.5 1.0
1.0
Downstream
0.5
0.5 0.0 0.5 1.0
(7)
Upstream
(8)
Downstream
0.5
Upstream
Downstream
0.0
0.0
0.0
0.0
0.5
0.5
0.5
1.0
1.0
1.0
0.5
1.0
0.5 0.0 0.5 1.0
1.0 0.5 0.0 0.5 1.0
0.5 0.0 0.5 1.0
0.5 0.0 0.5 1.0
–1
Over the ground speed (m s ) (northeast-southwest)
Figure 6. Over-the-ground velocities of herring during a ebb tide. Details as in Figure 5.
5, and 8 swam in an oriented fashion across the current
toward the shore of the estuary (Figure 8). As a result all
fish remained in the same general location during this
phase of the tide (Figures 2 and 3). Through-water mean
vector speeds during ebb tides indicate that the seven
herring were swimming against the tide at similar speeds
(0.447 m s 1, s.e.=0.045) and in similar directions
(Table 3).
Vertical movements
In 1987 the tracked herring were equipped with depthsensitive transmitters. These fish did not vary their depth
1294
K. N. Lacoste et al.
Table 2. Gross speed and upriver progress rate of herring relative to 30T during flood and ebb tides.
Area
of travel
Fish
number
Duration
(hh:mm)
1
2
3
4
5
6
7
8
01:15
02:59
27:05
17:56
05:48
06:04
09:02
14:30
South shore
|I. Lièvres
South Channel
Upriver progress rate
(m s 1)
Gross speed
(m s 1)
Flood
0.71
0.89
1.32
0.94
0.70
0.48
0.40
Ebb
0.97
0.58
0.63
0.84
0.39
0.68
0.45
Flood
0.34
0.36
0.73
0.53
0.01
0.11
0.15
Ebb
Net
0.53
0.12
0.02
0.25
0.02
0.25
0.16
0.24
0.71
0.28
0.01
0.14
0.01
Note: Herring 1 was not tracked during ebb tide while herring 2 was not tracked during flood tide.
Table 3. Over-the-ground (O.G.) and through-water (T.W.) speeds and directions of mean vectors for
herring tracked during flood and ebb tides. See also Figures 5–8.
Speed (m s 1)
Fish
no.
1
2
3
4
5
6
7
8
Flood
Direction (30T)
Ebb
O.G.
T.W.
0.353
0.438
0.441
0.768
0.513
0.017
0.128
0.162
0.293
0.601
0.576
0.456
0.345
0.426
Flood
O.G.
T.W.
0.615
0.163
0.056
0.271
0.125
0.261
0.212
0.484
0.322
0.507
0.453
0.657
0.378
0.329
Ebb
O.G.
T.W.
165
165
186
195
204
349
219
169
239
214
289
338
326
328
O.G.
T.W.
344
349
286
12
291
9
44
98
141
155
122
161
144
116
Note: Herring 1 was not tracked during ebb tide while herring 2 was not tracked during flood tide.
according to tidal phase (Figure 9). Instead they generally maintained a constant distance from the bottom but
this distance varied among fish. Mean fish-depth was
5.6 m (s.e.=0.18) and ranged from 0 to 15.2 m while
mean fish distance off the bottom was 3.84 m
(s.e.=1.17).
Discussion
Catch data (Côté and Powles, 1978) and tag returns
(Greendale and Powles, 1980) indicate that herring
travel upriver during their pre-spawning migration into
the St Lawrence estuary. This study is the first to
describe movements of clupeoids in relation to tidal
currents and is also the first to describe pre-spawning
behaviour of herring in that estuary and is therefore of
some importance despite its small sample size.
In 1987, Munro et al. (1998) discovered a major
spawning ground along the north side of the southwestern tip of |Ile aux Lièvres for which they provided a
comprehensive description. They located the spawning
site only three weeks after herring were tracked near |Ile
aux Lièvres in 1987 (this study). Therefore it is likely
that the herring tracked near the island in 1987 formed a
pre-spawning aggregation (Dragesund, 1980; Haegele
and Schweigert, 1985; Hae, 1985) which remained in the
area until favourable spawning conditions occurred (see
location of |Ile aux Lièvres spawning site on Figure 1).
This site does not seem to be used every year. According
to larval concentrations in the Pot-à-l’eau-de-vie
Channel, herring eggs were probably abundant there in
1980 and 1985 (Fortier and Gagné, 1990). The spawning
ground also seemed to have been used in 1992 according
to the local concentration of belugas and other
recognised egg consumers (Lesage and Kingsley, 1995).
However, eggs could not be found at the tip of |Ile aux
Lièvres in 1996 (Bédard et al., 1997) nor in 1998 (J.M.,
unpublished data).
Although no spawning sites have yet been found
along the south shore of the St Lawrence most
islands along the southern littoral, from Rimouski to
Kamouraska, are also believed to be used as spawning
sites concurrently with or alternately to that of the |Ile
aux Lièvres. Among these sites the |Iles aux Pèlerins area
Influence of tidal streams on pre-spawning Atlantic herring
(1)
(3)
Upstream
Downstream
1.0
Upstream
(4)
Downstream
1.0
Upstream
Downstream
0.5
0.5
0.5
0.0
0.0
0.5
0.5
0.0
0.5
1.0
1.0 0.5 0.0 0.5 1.0
1.5 1.0 0.5 0.0 0.5
–1
Swimming speed (m s ) (northwest-southeast)
1.0
1295
(5)
1.0
Upstream
Downstream
1.0
(6)
Upstream
1.0
Downstream
(7)
Upstream
Downstream
1.5 1.0 0.5 0.0 0.5
1.0
0.5
0.5
0.5
0.0
0.0
0.0
0.5
0.5
0.5
1.0
1.0
1.0
(8)
Upstream
Downstream
0.5
0.0
0.5
0.5 0.0 0.5 1.0
1.0 0.5 0.0 0.5 1.0
1.0 0.5 0.0 0.5 1.0
0.5 0.0 0.5 1.0
–1
Swimming speed (m s ) (northeast-southwest)
Figure 7. Through-water velocities of herring during a flood tide. Details as in Figure 5.
Upstream
1.0
Downstream
(3)
Upstream
1.0
Downstream
(4)
Upstream
0.5
0.5
0.0
0.0
0.5
0.5
1.0
1.0
Downstream
0.5
1.0
1.5
1.0 0.5 0.0 0.5 1.0
1.0 0.5 0.0 0.5 1.0
–1
Swimming speed (m s ) (northwest-southeast)
(2)
0.0
1.0
(5)
1.0
(6)
1.0
1.0 0.5 0.0 0.5
(7)
(8)
0.5
0.5
Upstream
Downstream
0.5
Upstream
Downstream
0.5
Upstream
Downstream
Upstream
Downstream
0.0
0.0
0.0
0.0
0.5
0.5
0.5
1.0
1.0
1.0
0.5
1.0
0.5 0.0 0.5 1.0
1.0 0.5 0.0 0.5
1.0 0.5 0.0 0.5
1.0 0.5 0.0 0.5
–1
Swimming speed (m s ) (northeast-southwest)
Figure 8. Through-water velocities of herring during an ebb tide. Details as in Figure 5.
is thought to be the most important one, comparable, in
fact, to the |Ile aux Lièvres site (Munro et al., 1998).
Concentrations of newly hatched larvae were reported
downstream of |Iles Les Pèlerins in June 1973 and 1974
(Able, 1978), and in 1978 (Auger and Powles, 1980).
Concentrations were also found directly downstream
from Pointe aux Orignaux and |Iles Kamouraska in June
1974 (Able, 1978), i.e. upriver from |Ile les Pèlerins. The
presence of other spawning sites along the south shore of
the Estuary, in particular the |Iles Les Pèlerins and |Iles
Kamouraska sites, might explain why herring tracked
near the coast (1986) swam upriver and parallel to the
coastline.
The tracked herring adopted different swimming
behaviours depending on the area where they were
tracked. Those travelling near the coast were generally
travelling upriver regardless of tidal phase and swam
actively with the current at flood tide and actively
1296
K. N. Lacoste et al.
0
Herring 5
5
Herring
Seafloor
10
15
1
0
Herring 6
5
Depth (m)
10
15
0
Herring 7
5
10
15
0
Herring 8
5
10
15
12
16
20
24
04
Time of day (h)
08
12
Figure 9. Depth of herring tracked in relation to tidal cycle
and seafloor. Solid horizontal bars on x-axis indicate tidal
cycle (above axis: flood; below axis: ebb). Note (1) identifies
maximum seabed depth (up to 30.1 m) reached in tracking of
herring 5.
against it during ebb tide to counteract the effects of the
downstream current. This swimming behaviour allowed
them to take advantage of flood currents and to travel
considerable distances upriver (e.g. herring 3 travelled
close to 25 km in a single day while herring 4 travelled
close to 32 km in 1.5 days). In contrast the fish near
the island (1987) swam in an oriented fashion against
tidal currents during both phases of the tide. The net
result of such swimming behaviour was that the fish
remained in the same location. In contrast, herring
tracked near the southern shore of the estuary seem to
have been migrating upriver towards an unknown
spawning site.
Maximum current speeds in the study area are of the
order of 1 m s 1 (Canadian Hydrographic Service,
1997). Currents d0.4 m s 1 (the mean swimming speed
of tracked herring) opposing upriver movements occur
during the 3 h before low tide. At that time the fish did
not swim fast enough to completely counteract the
effects of the tide, which resulted in net loss of ground.
Since swimming speeds were virtually constant during
the period of tracking, regardless of tidal phase, the
herring probably swam at preferred speeds in order to
minimise energy consumption thus optimising endurance during migration. They swam at speeds much lower
than 1.02 m s 1, which is their estimated maximum
sustainable swimming speed (i.e. the maximum swimming speed the fish can maintain for 200 minutes; He
and Wardle, 1988). They actually maintained an average
speed of 0.44 m s 1, well within the range of preferred
swimming speeds (0.30–0.56 m s 1) reported by He and
Wardle (1988).
Herring swimming near the island showed no signs of
using selective stream transport as they were swimming
against tidal streams during both phases of the tide,
presumably to maintain position. In contrast herring
tracked near the coast would have seemed more likely to
use selective tidal stream transport since they did not
appear to be close to their spawning site and thus
presumably were still en route. Typically, selective tidal
stream transport is defined by two components: the use
of tidal currents to assist in horizontal movements when
currents flow in the migratory direction and a vertical
movement to hold position on the bottom when currents
flow in the opposite direction.
Herring tracked near the coast appear to have made
use of tidal currents to facilitate their upriver migration
but without resorting to selective tidal stream transport.
During flood tides, they swam with the transporting tide
while during ebb tides, they swam against tidal currents
and seemed more oriented than during flood tides.
Herring 8, the only herring tracked near the coast with a
depth-sensitive transmitter, did not perform semidiurnal vertical migrations synchronised with the tides.
It seems unlikely, in any case, that herring migrating
near the coast would make regular vertical movements
synchronised with tides since the area is characterised by
shallow depths (<10 m) with vertically homogeneous
currents (Canadian Hydrographic Service, 1997; Saucier
and Chassé, 2000).
Although the herring did not change depth in relation
with the tides, tracks of fish near the coast showed
some behaviour patterns similar to those in studies
demonstrating selective tidal stream transport in other
fish species (e.g. Greer Walker et al., 1978). Ground
speeds were low and tracks convoluted when tides were
against the direction of fish migration, for example, while
ground speeds tended to be high and tracks straight when
tides were in the migratory direction. Furthermore the
Influence of tidal streams on pre-spawning Atlantic herring
tracked herring did not drift passively with the current
but rather swam actively, either with the current if it
was in the migratory direction or against the current if
counter to the migratory direction. Selective tidal
stream transport is a migratory behaviour that is energetically advantageous in areas of strong currents
(Weihs, 1978; Metcalfe et al., 1990). When considering
the lengths of our herring and current speeds in the
study area it seems that selective tidal stream transport
would have been energetically more efficient than continuous swimming (see Figure 5 in Metcalfe et al.,
1990). It is possible that only those species ecologically
associated with the bottom and that can take advantage
of the weaker currents of the bottom-boundary layer by
holding position on the bottom, will use selective tidal
stream transport. As a pelagic species herring is not
usually associated with the bottom, although it is a
bottom spawner.
Swimming behaviour was characterised by changes
in fish heading associated with changes in the
direction of tidal streams. It seems unlikely that fish were
in frequent visual contact with the bottom since they
were in turbid waters of the St Lawrence estuary and
changed headings at night as well as during daylight
hours. This suggests that herring can orient according to
tidal flow by non-visual clues, as has been suggested
or demonstrated before in other species (e.g. Metcalfe
et al., 1993).
In summary, there is no evidence of tidally synchronised movements normally associated with selective tidal
stream transport (with the important caveat that there
was only one depth-sensitive transmitter among the fish
moving along the coast). Herring migrating up the
estuary swam in the same direction on both ebb and
flood tides gaining more ground on flood tides than they
lost on the ebb. Movements were more oriented against
ebb tides than with flood tides. Fish that appeared to be
close to their spawning ground swam against both tides
and remained in the same location.
Acknowledgements
We thank Alain Armellin, Marlène Heppell, and
especially Jean-Guy Rondeau and Richard Plante who
played key roles during field operations. The Canadian
Hydrographic Service graciously provided research
vessels along with the services of an experienced pilot,
Pierre Poirier, whose help was greatly appreciated.
Brigitte Lévesque interpolated fish positions. Laure
Devine’s review of an earlier version substantially
improved the manuscript. We also thank Drs G. P.
Arnold and J. D. McCleave for thoughtful reviews. The
Department of Fisheries and Oceans of Canada funded
this project.
2001 Crown copyright
1297
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