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Movement Patterns of Hooded Seals ( Cystophora cristata ) in the Northwest Atlantic Ocean During the Post-Moult and Pre-Breed Seasons

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Movement patterns of hooded seals (Cystophora cristata) in the Northwest Atlantic in the pe-riod following moulting and prior to breeding are not well known. Here, we describe in detail the movement patterns of 21 seals for this period based on information gathered from satellite linked time depth recorders (SLTDRs). This study provides important baseline information necessary to understand the ecological requirements and patterns in habitat selection for the species. Adult and sub-adult hooded seals were tagged with SLTDRs directly after moulting in SE Greenland during July 2004, 2005 and 2007. Due to variation in tag date and arrival date to the breeding grounds, data between 1 Aug–28 Feb were used which gave all seals a track duration of 211 days (212 in 2005) except for one juvenile where the tag lasted for only 154 days. The tags yielded 36 107 loca-tion fixes (SD = 410.64, mean = 1 719.38). Although there was individual variation between seal trajectories during migration, the population shared a similar overall pattern. After moulting in July individuals travelled along the continental shelf area up to Davis Strait and Baffin Bay, thereafter moving southwards along the Labrador shelf until they arrived at the breeding grounds by March. Females tended to cut across the Labrador Sea and arrived at the Labrador shelf before heading up to the Baffin Bay area, while males tended to move straight there. The majority of the seals ended up at the Front (off Newfoundland and Southern Labrador) by March although a few of the tagged seals may have belonged to the Davis Strait breeding population and one male belonged to the Gulf of St. Lawrence breeding population. Seven seals displayed an eastward migratory pull and might have overlapped with the Northeast Atlantic population. This would support the theory of a panmitic population structure.
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Movement Patterns of Hooded Seals (Cystophora cristata) in
the Northwest Atlantic Ocean during the Post-Moult
and Pre-Breed Seasons
Julie M. Andersen and Yolanda F. Wiersma
Department of Biology, Memorial University of Newfoundland,
St. John’s, NL Canada E-mail: j.m.andersen@mun.ca
Garry Stenson
Science Branch, Department of Fisheries and Oceans,
Northwest Atlantic Fisheries Centre, St. John’s, NL Canada
Mike O. Hammill
Dept. of Fisheries and Oceans
Mont Joli, Quebec. Canada
Aqqalu Rosing-Asvid
Greenland Institute of Natural Resources
Box 570, 3900 Nuuk, Greenland
Andersen, J. M., Y. F. Wiersma, G. Stenson, M. O. Hammill, and A. Rosing-Asvid. 2009.
Movement Patterns of Hooded Seals (Cystophora cristata) in the Northwest Atlantic
Ocean During the Post-Moult and Pre-Breed Seasons. J. Northw. Atl. Fish Sci., 42: 1–11.
doi:10.2960/J.v42.m649
Abstract
Movement patterns of hooded seals (Cystophora cristata) in the Northwest Atlantic in the pe-
riod following moulting and prior to breeding are not well known. Here, we describe in detail the
movement patterns of 21 seals for this period based on information gathered from satellite linked
time depth recorders (SLTDRs). This study provides important baseline information necessary to
understand the ecological requirements and patterns in habitat selection for the species. Adult and
sub-adult hooded seals were tagged with SLTDRs directly after moulting in SE Greenland during
July 2004, 2005 and 2007. Due to variation in tag date and arrival date to the breeding grounds,
data between 1 Aug–28 Feb were used which gave all seals a track duration of 211 days (212 in
2005) except for one juvenile where the tag lasted for only 154 days. The tags yielded 36 107 loca-
tion xes (SD = 410.64, mean = 1 719.38). Although there was individual variation between seal
trajectories during migration, the population shared a similar overall pattern. After moulting in July
individuals travelled along the continental shelf area up to Davis Strait and Bafn Bay, thereafter
moving southwards along the Labrador shelf until they arrived at the breeding grounds by March.
Females tended to cut across the Labrador Sea and arrived at the Labrador shelf before heading up
to the Bafn Bay area, while males tended to move straight there. The majority of the seals ended
up at the Front (off Newfoundland and Southern Labrador) by March although a few of the tagged
seals may have belonged to the Davis Strait breeding population and one male belonged to the Gulf
of St. Lawrence breeding population. Seven seals displayed an eastward migratory pull and might
have overlapped with the Northeast Atlantic population. This would support the theory of a panmitic
population structure.
Keywords: Cystophora cristata, distribution, hooded seals, movement patterns, Northwest
Atlantic Ocean
J. Northw. Atl. Fish. Sci., Vol. 42: 1–11 Upload date 21 July 2009
http://journal.nafo.int
J. Northw. Atl. Fish. Sci., Vol. 42, 2009–2010
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Fig 1. Reference map of the Northwest Atlantic showing locations mentioned in the text.
Introduction
The hooded seal (Cystophora cristata) is an abun-
dant, pelagic, deep-diving pinniped distributed through-
out the North Atlantic and adjacent Arctic Oceans
(Sergeant, 1974; Folkow and Blix, 1995, 1999;
Hammill and Stenson, 2006). They breed synchronously
during mid- to late March on the pack ice around Jan
Mayen (“West Ice”), in Davis Strait between Bafn Is-
land and western Greenland, in the Gulf of St. Lawrence
(the “Gulf”) and off southern Labrador and/or northern
Newfoundland (the “Front”) (Fig. 1) (Sergeant, 1974,
1976; Hammill, 1993; Folkow et al. 1996). These four
breeding herds are considered to belong to two putative
populations (Hammill and Stenson, 2006). Hooded seals
whelping near Jan Mayen are thought to constitute the
Northeast (NE) Atlantic population while hooded seals
whelping and breeding in Davis Strait, the Gulf and
ANDERSEN et al.: Hooded Seal Movements 3
at the Front are all thought to belong to the Northwest
(NW) Atlantic population (Hammill and Stenson, 2006).
The total NW Atlantic population has been estimated
to consist of approximately 600 000 animals (593 500,
SE = 67 200, Hammill and Stenson, 2006), of which
90% are estimated to whelp at the Front (Stenson et al.,
2006). The NE Atlantic population is likely to number
between 70 000 and 90 000 animals, although there is
considerable uncertainty around these estimates due to
paucity of data and limited understanding of the relation-
ships between whelping areas (WGHARP, 2006).
Coltman et al. (2007) carried out a genetics study
across the two populations and found that the Greenland
Sea breeding herd was genetically most distant from the
NW Atlantic breeding areas; however, the difference
was statistically non-signicant. The results indicated
that the world’s hooded seals belong to a single panmitic
genetic population, thereby suggesting that there is some
overlap in distribution between the NE Atlantic and the
NW Atlantic populations. The herd belonging to the NE
Atlantic population and whelping around Jan Mayen dis-
perses to sea after breeding in March and some individu-
als return to the pack ice in the same area in July to moult
(Øritsland, 1959; Rasmussen, 1960) while the majority
moult further north (Folkow et al., 1996). Following
breeding, NW Atlantic hooded seals leave the whelp-
ing areas to feed and eventually migrate to the ice off
southeast Greenland where they moult in July (Stenson,
unpublished data; Sergeant, 1974). After moulting, the
general hypothesis has been that most of these animals
disperse across the NW Atlantic and up to Davis Strait
(Rasmussen, 1960) before migrating southward to the
whelping areas.
Preliminary studies have indicated that hooded seals
spend much of their time along the edges of the Cana-
dian and Greenland continental shelves or sea mounts
(e.g., Flemish Cap, Reykjanes Ridge) where they dive to
depths of over 1 500 m (Stenson and others, unpublished
data). Due to their pelagic distribution and the lack of
knowledge regarding their prey selection at various
times of the year, the extent of their sh consumption is
difcult to assess (Folkow et al., 1996). However, diet
studies indicate that adult hooded seals mainly forage
on benthopelagic species (Ross, MS 1992; Hammill and
Stenson, 2000; Haug et al., 2007). To a great extent, the
role of hooded seals in the marine ecosystem is virtu-
ally unknown. However, satellite telemetry allows us to
monitor movements of free ranging pinnipeds through-
out the year, providing data that have previously been
difcult to obtain.
Data from the tags provide us with valuable knowl-
edge of the general movement pattern for hooded seals
during the post-moult and pre-breed period which has
not been possible to obtain previously. Historical infor-
mation on marine mammal distributions was provided by
shore-based observations, incidental observations from
commercial hunting and capture of branded or tagged in-
dividuals (Rasmussen, 1960; Sergeant, 1974, MS 1979;
Hammill and Stenson, 2006). Although useful, these ob-
servations provide more information about the observer
effort then the actual distribution of the animals. Satellite
telemetry is therefore very valuable in terms of offering
continuous distribution information throughout the year
which can be projected onto a population level. Here the
movement patterns of 21 seals equipped with satellite
transmitters were examined for the post-moult and pre-
breed period (July–March) of their annual migration.
Methods
Adult and sub-adult hooded seals were tagged with
Satellite Linked Time Depth Recorders (SLTDRs) di-
rectly after moulting in July in SE Greenland (2004,
2005 and 2007) ( approx. 65°N 37°W). The animals were
captured using a net, weighed, and tranquilized using
tiletamine hydrochloride and zolazepam hydrochloride
(Telazol, AH. Robins Company, Richmond, VZ, USA)
administered intramuscularly (1 mg per 100 kg). The
SLTDRs were designed by the Sea Mammal Research
Unit (SMRU) in St. Andrews, Scotland. The transmit-
ters were attached to the head or neck of the seal, using
quick drying epoxy glue (Cure 5, Industrial Formulators
of Canada Ltd. Burnaby, BC Canada) and the seals were
released immediately upon recovery from the tranquil-
izer. The tag may last up to a year, and is lost when the
seal moults the following year.
Seal Locations
Locations at the surface were determined by the Ar-
gos system, and subsequently ltered using an algorithm
based on the travelling speed of the tracked animal, dis-
tance between successive locations and turning angle
(Freitas et al. 2008). We used the algorithms default
swim speed of of 2m/s.
Distribution maps (Figs. 2 and 3) were created using
ArcGIS 9.3 (Environmental Systems Research Institute,
Redlands, CA) where the points are represented by l-
tered locations of seal uplinks throughout their migra-
tion. Kernel density maps (Figs. 4 and 5) were created
using the package “spatstat” in R (version 2.8.0, The
R Foundation for Statistical Computing) and are based
on the total number of ltered uplink locations. These
density plots are created using a Gaussian kernel to cre-
ate smoothed histograms where “sigma” determines the
bandwidth of the kernel. Narrower bandwidths yield
J. Northw. Atl. Fish. Sci., Vol. 42, 2009–2010
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km
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Fig 2. All 21 hooded seal tracks (ltered data) during the study period running from 1 Aug to 28 Feb which is the post-
moult pre-breeding migration period for this species. Dashed line is the 1 000 m contour line.
more extreme values and broader bandwidths narrow the
interquartile range. The bandwidth used for this study
was a sigma value of 0.75. The darker areas represent
locations where the presence of seals caused a higher
number of uplinks indicating more time spent in those
areas. The resolution of the grid is 20 000 meters.
Results
A total of 26 seals with a post-moulting body mass
(BM) range of 73.5–194 kg were caught at approximate-
ly at 65°N 37°W in SE Greenland in July 2004, 2005 and
2007. Of the 26 seals tagged, 5 were excluded due to mal-
ANDERSEN et al.: Hooded Seal Movements 5
70°N
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February
December
October
August
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20°W30°W40°W50°W60°W
January
November
September
0750 1 500
km
Fig 3. Monthly movements of satellite
tagged hooded seals based on ltered
uplink data. Light grey symbols are
juvenile, darker grey female and black
are males. Dashed line is the 1 000 m
contour line.
J. Northw. Atl. Fish. Sci., Vol. 42, 2009–2010
6
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km
0 750 1 500
Fig 4. Kernel density surface map displaying the areas of high-use by hooded seals in the NW Atlantic Ocean during the
full post-moult pre-breeding migration period based on ltered uplink data. Dashed line is the 1 000 m contour
line. Resolution is 20 km.
function within one month of the actual tag date, yielding
a sample size of 21 seals (9 adult females, 8 adult males
and 4 juveniles (3 females and 1 male)). Data on the indi-
vidual seals are presented in Table 1 together with actual
tagging locations. Fig. 2 presents combined tracks for
the entire study period and Fig. 4 shows the high use ar-
eas averaged over the same period. One tag transmitted
for 154 days, whereas the rest lasted the entire study pe-
riod (18 tags = 211 days, 2 tags = 212 days (2005)). The
tags had a combined transmission period of 4 376 days
and provided (after ltering) 36 107 uplink xes (SD =
410.64), which gives an average number of 173.31 up-
links each day per seal. The mean total travel distance
throughout the period was 14 142.05 ± 2 038.92 km.
ANDERSEN et al.: Hooded Seal Movements 7
70°N
60°N
50°N
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60°N
50°N
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60°N
50°N
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20°W30°W40°W50°W60°W
February
December
October
August
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January
November
September
0750 1 500
km
Fig 5. Kernel density surface map display-
ing areas of high-use by hooded
seals in the NW Atlantic Ocean per
month during the post-moult pre-
breeding migration period (August–
February) based on ltered uplink
data. Dashed line is the 1 000 m con-
tour line. Resolution is 20 km.
J. Northw. Atl. Fish. Sci., Vol. 42, 2009–2010
8
Year PTT # Sex Wt (kg) Start End
Days
transmitting
Latitude
tagged
Longitude
tagged
2004 44444 F 116 01 Aug 28 Feb 211 66°15'N 34°17'W
2004 44487 M 155 01 Aug 03 Jan 154 66°08'N 34°35'W
2004 44443 F 85 01 Aug 28 Feb 211 66°10'N 34°27'W
2004 44489 M 172 01 Aug 28 Feb 211 66°09'N 34°30'W
2004 49539 F 81 01 Aug 28 Feb 211 66°15'N 34°17'W
2005 44486 F 112 01 Aug 28 Feb 211 65°28'N 36°13'W
2005 44450 M 127 01 Aug 28 Feb 211 65°31'N 36°21'W
2005 44448 F 90 01 Aug 28 Feb 211 65°29'N 37°00'W
2005 44488 F 138 01 Aug 28 Feb 211 65°30'N 36°19'W
2005 49540 M 194 01 Aug 28 Feb 211 65°31'N 36°14'W
2005 49530 M 146 01 Aug 28 Feb 211 65°25'N 36°37'W
2005 49533 F 138 01 Aug 28 Feb 211 65°20'N 37°03'W
2005 49531 F 95 01 Aug 28 Feb 211 65°20'N 37°06'W
2005 49537 M 174 01 Aug 28 Feb 211 65°25'N 37°01'W
2005 49534 F 117 01 Aug 28 Feb 211 65°19'N 37°11'W
2005 49535 F 98 01 Aug 28 Feb 211 65°19'N 37°11'W
2005 49529 F 114 01 Aug 28 Feb 211 65°22'N 37°20'W
2005 44503 M 109 01 Aug 28 Feb 211 65°23'N 37°22'W
2007 44417 F 73.5 01 Aug 29 Feb 212 65°26'N 37°18'W
2007 44419 M 97.5 01 Aug 29 Feb 212 65°23'N 37°48'W
2007 44425 F 130 01 Aug 29 Feb 212 65°23'N 37°55'W
TABLE 1. Year, Argos PTT identification number, sex, weight at tag date, start and end dates for
study period, days transmitted and tagging location of NW Atlantic hooded seals.
Due to different tag dates and arrival to the breed-
ing ground, the study period was selected to run from
1 August to 28 February.
The majority of the seals fanned out quite widely,
but in similar directions (across the Labrador Sea) im-
mediately after moulting (Fig. 3). The majority of fe-
males moved across the Labrador Sea to the Labrador
Shelf and Front area, while the males chose a more direct
route up to the Davis Strait and Bafn Bay area along the
continental shelf off western Greenland. Seven animals
stayed behind in Greenland for a longer period of time:
one female juvenile (#44443) stayed in the moulting area
throughout the migration period apart from a few shorter
trips along the SE Greenland coast and into the Denmark
Strait. This female never migrated to the breeding areas.
A young male (#44487) stayed behind in the moulting
areas until November, at which point he started to move
south, crossing the Labrador Sea towards the Front in
December. The signal was lost on 3 January 2005 when
the male was mid basin. Female #44488 moved north-
east into the Denmark Strait and did not migrate across
the Labrador Sea towards the Front until December.
This female then stayed in the Front area until breeding.
Male #44489 was the only seal to head straight north-
east through the Denmark Strait following the Green-
land shelf all the way up to the area off Danmark Havn
(~ 75º07'N 13º03'W). This male picked up speed in
October and headed south straight across the Labrador
Sea to the Front. Male #44503 migrated north following
the same pattern as #44489, but turned around and mi-
grated south of Iceland, along the Faeroe-Iceland ridge
and back on the north side of Iceland, ending up in the
Denmark Strait by the end of February. Male #49537
stayed in the moulting area the entire time until Febru-
ary when it abruptly migrated to the Front. Only one of
the tagged seals was a Gulf breeder (#49540) and was
the only male to cut straight across the Labrador Sea
after moulting to the Front before heading up along
the continental shelf area. This seal made a quick loop
into Bafn Bay before heading back down to the Front
by end of November and from there travelled south of
Newfoundland arriving in the Gulf of St. Lawrence by
the end of December. Males #44450 and #44419 ended
ANDERSEN et al.: Hooded Seal Movements 9
up in Davis Strait by end February indicating that they
were not breeding or they may have belonged to the Da-
vis Strait breeding herd.
Although the seals fanned out in various directions
in August, many of them gathered in Bafn Bay and
Davis Strait by October and November which may indi-
cate that these are important feeding areas for the popu-
lation (Figs. 3 and 5). The Labrador shelf, the Front and
SE Greenland may also be important habitat locations
for this species based on travel and kernel density pat-
terns (Fig. 5). The rest of the study area seemed to be
used for travelling or shorter foraging trips.
Discussion
This study is the rst to illustrate the movement
patterns of the NW Atlantic hooded seals during their
post-moult, pre-breed migration. To date, there has been
limited information about the annual migration of this
species, but this study reveals that they travel large dis-
tances during this time. Although there is individual
variation in trajectories chosen, the overall picture of
how these animals move throughout the NW Atlantic
seem to be similar throughout the population. This dif-
fers somewhat to Folkow et al.’s (1996) ndings for the
NE Atlantic population’s migration pattern. They found
that the migrations of these seals to distant waters were
not synchronised in time and that they did not display a
general seasonal migration pattern (Folkow et al., 1996).
However, the NW Atlantic population did demonstrate a
similar pattern in choice of feeding areas and there was
general synchrony, with some individual variation. The
seals all started their migration after their annual moult
and seemed to head in various directions. However, most
start to come together in September along the continental
shelf, Davis Strait and in Bafn Bay (Fig. 3), presumably
for feeding as this is an important period for them to put
on weight after the moult and preparing themselves for
the whelping and breeding season. The choice of feed-
ing areas appear to be closely related to areas of high
topographic relief as the seals tend to stay close to the
1000 m contour line along the Labrador shelf area as
well as in the Bafn Bay basin. Bafn Bay and the east-
ern Canadian High Arctic have a complex coastline, an
inux of warm Atlantic water along the West Greenland
coast, and a restricted opening to the polar basin through
Robeson Channel (Heide-Jørgensen and Laidre, 2004) in
the north. This results in numerous microhabitats in the
region which may result in the high abundance of ani-
mals overwintering there (Heide-Jørgensen and Laidre,
2004). Some species which overlap with the range of
hooded seals in this area include marine mammals such
as beluga (Delphionpterus leucas), narwhal (Monodon
monoceros) and bowhead whales (Balaena mysticetus),
as well as various species of seabirds (Heide-Jørgensen
and Laidre 2004; Laidre et al., 2003, 2004, 2007). There
may be some overlap in prey preference between belu-
ga, narwhal and hooded seals (e.g., Greenland halibut
(Reinharditus hippoglossoides)) (Richard et al., 1998;
Laidre et al., 2004) in these areas. The aspects of how
oceanographic processes and prey distribution may drive
hooded seal habitat use (including their diving behaviour
throughout their migration) will be the subject of future
research.
Areas along the Labrador shelf and the Bafn Bay
basin appear to be important feeding areas while the
Labrador Sea and the west coast of Greenland appear to
be areas where the seals move through at a higher speed
(Fig. 4). Even though the seals may have a wide move-
ment range during certain months (Fig. 3), the high-use
areas are actually rather small (Fig. 5). Some of the high-
use areas could be biased due to a higher number of seals
moving through a specic location during the month
resulting in a higher number of uplinks at a particular
point (e.g. Fig. 5: August is when the seals start mov-
ing out of the moulting patches which were located in
the same general area). It is not expected that hauling
out on ice will bias the results too much due to the fact
that the tags will stop transmitting if dry for more than
six hours. By September the seals arrived on the shelf
area in southern Davis Strait and in the southern Bafn
Bay basin. In October the seals appeared to spend more
time in the latter, while the movement range of the seals
during that month was very wide (Fig. 3). During the
month of November the seals display a more general use
of Bafn Bay and Davis Strait, and they started to move
south along the Labrador Shelf; by December they were
all south of Bafn Bay spending time in Davis Strait and
on the Labrador Shelf. That seals feeding in Bafn Bay
move south after November may be inuenced by the
build-up of ice in the area forcing the seals southwards.
Another possibility could be due to colder water temper-
atures forcing prey to deeper depths thereby increasing
the cost of feeding. January appears to be a month when
the seals stay in more restricted areas (Front and in the
Davis Strait) which could also be due to ice conditions,
while in February seals started to move across somewhat
longer distances again, perhaps to obtain a good position
for breeding. There was a high-use area in the southern
Denmark Strait which is caused by one seal’s intense use
of a small area that month. The rest of the seals were
spread out along the Front area and Labrador shelf up to
Davis Strait.
There appears to be a difference between sexes in the
initial choice of feeding areas. Females crossed the Lab-
J. Northw. Atl. Fish. Sci., Vol. 42, 2009–2010
10
rador Sea and arrived earlier onto the continental shelf
area off Labrador (Fig. 3, August), while males took a
more direct route up to Davis Strait and Bafn Bay. Be-
cause the hooded seal is a sexually dimorphic phocid,
the different choice in initial feeding area may be due
to different dietary requirements (Hammill and Stenson,
2000) after the moult. Recent studies have shown that
although there is an overlap between males and females
on a horizontal plane during feeding migrations after the
breeding season, they display differences in foraging
depths. Females tend to make more shallow dives than
males preceding the migration and deeper dives after the
migration (Bajzak et al., 2009). The feeding behaviour
and diving during post-moult and pre-breed seasons has
not yet been investigated; however this study indicates
that there is less horizontal overlap initially between
sexes during this period.
Two female juveniles (#49539 and #44417) migrat-
ed to Bafn Bay by the end of September, moving south
with the rest of the animals and ending up at the Front
by end of February. They may not have ended up at the
breeding patch by March, or they could possibly be rst
time breeders. Female #44486 arrived at the Front by the
beginning of February, but migrated back across the Lab-
rador Sea to Cape Farewell by the end. This may have
been a detour, or perhaps this female did not breed that
year. There is also a possibility that this female contin-
ued up to the West Ice where the NE Atlantic population
breeds in late March (e.g., Øritsland, 1959; Rasmussen,
1960).The seven seals which stayed behind in Greenland
for a longer period of time executing migrations up to
Denmark Strait and #44503 who travelled to Faroese
waters before ending up back in Denmark Strait by the
end of February offers a strong indication that there is an
overlap between the two populations, as has been sug-
gested in earlier studies (Rasmussen, 1960; Coltman et
al., 2007). The NE Atlantic population spends longer
periods of time in the Denmark Strait, around Iceland
and Jan Mayen (“West Ice”) and are found to be pres-
ent in waters off the Faeroe Islands during all months
of the year (Folkow et al., 1996). The ndings in this
study therefore support the genetic study carried out by
Coltman et al., (2007) who suggested that North Atlantic
hooded seals consists of one panmitic population.
This study provides new and valuable information
on the possible locations of critical habitat for hooded
seals. Further investigation of the telemetry data used
will include exploring how the physical environment af-
fects hooded seal migrations and their diving behaviour
throughout the full year. Such studies will improve our
understanding of the role this species play in the North-
west Atlantic ecosystem.
Acknowledgements
We would like to thank D. McKinnon and D.
Wakeham for help in capturing the seals and deploy-
ing the transmitters. Lise Langgård, Tore Haug, and
two anonymous reviewers provided valuable feedback
on an earlier draft of the manuscript. We would also
like to thank Roger Bivand at the Norwegian School
of Economics and Business Administration and the
LESA lab crew at Memorial University of Newfound-
land for valuable input. This work was funded through
the Atlantic Seal Research program, the International
Governance Program (DFO) and by Greenland In-
stitute of Natural Resources as well as a CFI grant
to YW.
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... Despite being subject to population declines and displacements resulting from hunting, habitat destruction, environmental pollutants, interspecific competition and pathogens, the harbour seal has demonstrated a remarkable ability to recover and recolonize former ranges when efficient conservation measures have been implemented (Brasseur et al., 2018;Cammen et al., 2018;Härkönen et al., 2006;. Taken together, these observations might suggest that harbour seals, similar to other northern phocids, are characterized by a high dispersal ability and limited population structure (Andersen et al., 2009;Carr et al., 2015;Coltman et al., 2007;Davis et al., 2008;Fietz et al., 2016;Klimova et al., 2014;Thompson et al., 1996). However, this is not the case. ...
... This observation is supported by tagging data from both North Atlantic and North Pacific harbour seal populations, which demonstrate that harbour seals perform foraging trips of up to several hundred kilometers, but almost always return to the same haul-out site or region and very rarely cross large open stretches of deep water (Carroll et al., 2020;Dietz et al., 2013;Peterson et al., 2012;Rosing-Asvid et al., 2020;Small et al., 2006;Womble & Gende, 2013). In contrast, other northern phocid species, such as the sympatric grey seal, as well as the Arctic harp (Pagophilus groenlandicus), hooded (Cystophora cristata) and ringed seals (Pusa hispida), regularly undertake long distance migrations and/or movements covering thousands of kilometers and cross open water (Andersen et al., 2009;Nordøy et al., 2008;Svetochev et al., 2016;Thompson et al., 1996;Yurkowski et al., 2016). The open water barriers to harbour seal dispersal are particularly prominent in the North Atlantic, where population connectivity appears to be reduced by a heterogeneous The harbour seal's success in colonising new habitats is likely due to several factors, which may collectively facilitate the occupation of more predator-exposed, marginal and dynamic environments than other seal species. ...
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... The hooded seal (Cystophora cristata) is an abundant, pelagic, deep-diving pinniped distributed throughout the North Atlantic and adjacent Arctic marine areas (Sergeant, 1974). Hooded seals spend most of the year dispersed and offshore, presumably foraging regularly outside the breeding and molting periods (Sergeant, 1974;Folkow and Blix, 1995;Folkow and Blix, 1999;Andersen et al., 2009). They breed synchronously during mid-to late March on the pack ice around Jan Mayen, in Davis Strait, in the Gulf of St. Lawrence (the Gulf), and off the northern coast of Newfoundland (the Front) (Sergeant, 1974;Hammill, 1993;Folkow et al., 1996;Bajzak et al., 2009). ...
... Habitats of hooded seals are difficult to survey during certain times of the year as they are inaccessible due to heavy pack ice, remoteness of those areas, and the requirement of expensive icebreaker ships and/or helicopters. Until now, information on hooded seal distributions has been provided by shore-based observations, capture of tagged individuals, vessel surveys, aerial surveys, and satellite telemetry methods (Sergeant, 1974;Hammill, 1993;Øritsland and Øien, 1995;Andersen et al., 2009). Significant gaps still exist in our knowledge about this species, some of which might be addressed using long-term passive acoustic monitoring (PAM). ...
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... The bulk of knowledge regarding the distribution of corals and sponges in Canadian waters is derived from random stratified research trawl surveys (Treble et al. 2000, Treble 2002and 2009, Wareham and Edinger 2007, Kenchington et al. 2010, complimented by opportunistic collections by Fisheries Observers on board commercial fishing vessels (Wareham andEdinger 2007, Wareham 2009 (Figure 16). ...
... Hooded seals are also highly migratory and spend their time at sea in between breeding and moulting seasons on sea ice. The Labrador Shelf acts as an important foraging area in between these seasons while the Labrador Sea acts as a migratory route (Anderson et al. 2009). For each age and sex class, Hooded seals utilize areas within the LSFA most during the fall (Figure 25). ...
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The ex istence is confirrned fr orn ae ri al survey of a whelping population of hooded seals in Davis Strait, reported in the nineteenth centur v, and numbering in the tens of thousands . This is believed to be the source of recruitment maintaining the population of hooded seals at icefields enst of Newfoundland where the species is heavily hunted. Locations and dates of tag and brand recoveries, frequent wandering of juveniles south of the regular range, and identity of breecling seasons al l suggest much mixing between populations in this species. Zusammenfassung: Durch Luftbeobachtung konnte die Existenz einer werfenden, einige Zehntausend Tiere zählenden Klappmützen-Population in Devis Strait bestätigt werden I Über die bereits im vergangenen Jahr­ hundert berichtet worden war. Es wird angenommen, daß die auf den Eisfeldern östlich von Neufundland stark bejagte Population aus diesen neu-nachgewiesenen Beständen eine ständige Auffrischung erfährt. Orte und Daten der Wlederfunda von durch Marken oder Brandzeichen gekennzeichneten Tieren, häufige Wan M dervorstöße von einzelnen Jungtieren südlich der Grenze regelmäßigen Vorkommens sowie die Dberein­ stimmung der Wurfzeiten deuten darauf hin, daß es zu einer starken Mischunq zwischen den Populationen dieser Art kommt. IntroducUon Hooded seals (Cystophora cristata Erxleben) are known to whelp during March-April in two areas of the North Atlantic: the larger population at the "West Ice " in the region of Jan Mayen Island, the sm aller, on pack ice northeast of Newfoundland, with a small fraction in the Gulf of St. Lawrence. The only known moulting areas are on pack ice east of Greenland in Denmark Strait, and from 74° to 76°N, in July-August (Fig. 1). What is known of the biology and relationship of these stocks was documented by 0ritsland (1959) and Rasmussen (1957, 1960). The present paper documents the rediscovery of a whelping ground arid discusses the interrelationships of stocks.
Article
Hooded seals, Cystophora cristata, are abundant in the North Atlantic. This paper reviews current knowledge on the distribution and dive behaviour of these seals. The stock which breeds in sea ice near Jan Mayen may count about 250,000 animals, but little is known about where they stay and what they eat outside the pupping season (March/April) and the moult (July). We used satellite tags to monitor movements and/or dive depths and durations of 19 seals, and we obtained data on ≈12,000 locations and ≈120,000 dives, between July 1992 and July 1993. After the moult, most of the seals dispersed to travel, once or repeatedly, between the ice off Greenland and the distant waters off the Faeroe Islands, south of Bear Island, or the Irminger Sea. After breeding, all seals again returned to sea to travel to the waters off northern Ireland, the Faeroes or the Norwegian coast. Hooded seals may dive repeatedly to >1,000 m and stay submerged for >52 min, but usually dive to 100–600 m depth. We suggest that the dietary preferences, and even the fish consumption of hooded seals in different areas may be assessed by comparing their dive depths with the distribution of potential prey.