JFM 2000 Quarterly Rpt. sidebar
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(Quarterly
Report for Jan-Feb-Mar 2000)
Steller
Sea Lion Research in the Aleutian Islands and Gulf
of Alaska
Scientists from the National Marine Fisheries
Service’s Alaska Fisheries Science Center,
Colorado State University, and the University of
Alaska Sea Grant Program conducted Steller sea lion
research in the Aleutian Islands region and Gulf of
Alaska aboard the U.S. Fish and Wildlife Service
vessel Tila from 24 February through 15 March 2000.
The primary goal of this cruise was to capture
juvenile and pup sea lions for collection of blood
and other biological samples and for deployment of
satellite-linked time-depth recorders. A
secondary goal was to go ashore at any accessible
haul-out site to collect sea lion scats (fecal
material) for food habits analyses. Capture
effort was concentrated in three geographical
regions: Seguam Island, the Krenitzen Islands
and Unimak Pass, and eastern Kodiak.
Itinerary
The scientific party boarded the Tila at Adak,
Alaska, on 24 February. Most of the cruise was
conducted under storm- or gale-warning flags, as a
succession of low-pressure weather systems swept
across the region, delivering high winds and heavy
seas. Several of our intended research sites
were fully exposed to weather (e.g., southwest winds
and seas washing directly onto Lake Point, Adak).
Other sites may have been on the leeward sides
of islands, but the lack of protection from surging
waves made them unworkable on most days (e.g.,
Seguam, Yunaska, and Jude Islands). Consequently,
we spent much of our time at anchor in shelter when
conditions precluded safe landings at haul-out
sites, striving to be in position to go ashore and
work when the weather did let up. This
strategy resulted in a very successful day of work
at Turf Point, Sequam Island. Even in the
relative protection of the Krenitzen Islands, we
constantly changed anchorages and target haul-out
sites in reaction to changes in wind direction and
speed. When we were able to land at haul-out sites
in the Krenitzen Islands, wind direction frequently
was exactly wrong for stalking sea lions. On
several occasions, all animals spooked and departed
from the haulout before a capture could be
attempted. We were unable to get ashore at
haul-out sites along the eastern coastline of Kodiak
Island (Twoheaded Island, Cape Barnabas, Gull Point,
Cape Chiniak) because of easterly winds and seas,
but we did have one workable day at Long Island near
Kodiak City and one day in the northern Archipelago
(Sea Otter Island and Latax Rocks). A severe
storm warning caused us to curtail our work a day
early. We concluded the cruise at Homer,
Alaska, on 15 March.
Results
During the Tila cruise, we visited 29 Steller sea
lion rookery and haul-out sites from Lake Point, on
Adak Island in the central Aleutian Islands region,
to Flat Island in lower Cook Inlet. We made no
attempt to land at 19 of these sites, either because
conditions prohibited safe landing or there were so
few animals hauled out that the low likelihood of
successful results did not warrant disturbance.
We successfully landed ashore at nine
different sites. On one occasion we went
ashore but were unable to reach the haul-out site
(Silak Island in Little Tanaga Strait). We
collected a total of 219 scats from ten shore visits
to nine different sites: 13 scats from Seguam, 174
scats from the Krenitzen Islands (five sites), and
32 scats from the northern Kodiak Archipelago (three
sites).
We captured nine pup and yearling sea lions: five
at Seguam Island (Turf Point: four females, one
male), two at Aiktak Island (one female, one male),
and two at Long Island (two males). Mean mass
was 82.2 kg (SD=14.3, range 61.8-100.2 kg) for five
females and 83.6 kg (SD=23.7, range 62.2-109.0 kg)
for three males. Mean mass for eight animals
of both sexes was 82.7 kg (SD=16.6). We were
unable to weigh one male (estimated to be 95-100 kg)
because of his struggling and the difficult position
where he lay. This male probably was 21!22
months old, based on the length of his canine teeth.
All others were pups of the year,
approximately 9!10 months old. We deployed
satellite-linked time-depth recorders (SLTDRs) and
VHF transmitters on eight of the nine captured sea
lions, not attaching instruments to the smallest of
the female pups captured at Sequam Island. Via
e-mail, we were able to notify colleagues at NMML
immediately after SLTDR deployment, receiving
confirmation within a few hours that each instrument
was working and that each animal had shown some
movement.
We successfully obtained blood from all captured
animals. We performed preliminary blood work
onboard the ship (e.g., serum extraction,
hematocrit, white cell counts). Samples
retained for later analyses in the laboratory
included frozen serum and plasma, hemoglobin
preserved in reagent, and blood smears on slides.
The white-cell counts were very low for
the two smallest pups, possibly an indication of
viral infection. One of these pups also had
ulcers on his foreflippers, possibly indicative of
calicivirus infection. The largest female
captured had an ulcer on her vulva that also may
have been caused by calicivirus; however, her
white cell count appeared within normal limits.
We collected a genetic sample (flipper punch)
from each captured animal, and a blubber biopsy from
all five animals captured at Seguam Island and both
animals captured at Long Island. The two
animals captured at Aiktak Island were marginally
restrained in an awkward setting and we decided to
forgo biopsy. Blubber will be used for fatty
acid studies as well as other analyses. Biopsies
of one of the smaller flipper ulcers on the male pup
at Long Island will be used for virology analysis.
Other observations
We collected a fresh-born fetus on Sea Otter Island,
at the northern end of the Kodiak Archipelago.
Judging from the overall condition of the
fetus, it had been born a few hours prior to our
arrival. Partial inflation of the lungs implied that
the pup had been born alive but had not survived
more than 15-30 minutes. Dr. Terry Spraker of
Colorado State University performed a postmortem
examination onboard the ship and collected a full
suite of formalin-preserved and frozen tissues for
laboratory analyses. We also collected blood
from the fetus, which we worked up according to the
same protocols as for the live pups.
We had only two resightings of tagged animals.
Both were tagged as new-born pups at Ugamak
Island on 2 July 1998. We saw no branded sea
lions during the cruise. In addition, we had
surprisingly few observations of other marine
mammals. We saw killer whales on only three
occasions: two whales in Amukta Pass on 3 March,
four whales in Tigalda Bay on 7 March, and five
whales cruising processor row in Kodiak harbor on 12
March. We were unable to obtain photographs of
any killer whales. On 3 March a group of 6-10
Pacific white-sided dolphins rode our bow for
several minutes north of Akutan Island, near Unimak
Pass.
The most notable bird observation was of a male
spectacled eider off the sea lion haulout on the
rocks northeast of Tigalda, a site identified as
“Kaligagan Rocks” by the Alaska Maritime
Wildlife Refuge biologists. It is thought that
most spectacled eiders winter in polynyas (open
waters in sea ice) in the Bering Sea near St.
Lawrence and St. Matthews islands. The few
sightings of these birds in the Aleutian Islands
during winter likely is a function of low observer
effort.
Summary
The capture technique of using hand-held hoop
nets on land worked very well. This was only
the second time we have applied this technique to
Steller sea lions in Alaska. The
technique does require liberal adaptation and
improvisation to cope with the physiography of each
site, local weather conditions, and haul-out
distribution of the animals. On three
occasions we experimented with using the skiff
immediately in front of the haulout to herd and
distract animals and drive them towards the capture
team, who crept up from behind. The
skiff-aided technique was successful at one haul-out
site but yielded only near misses at two others.
Favorable weather, of course, is key to the
success of any field operations in maritime Alaska,
particularly in midwinter. Captures are
difficult at best when forced to approach animals
from up-wind, and impossible when conditions prevent
landing the scientific party on the beach.
We administered a dose of valium (1.1-2.0 cc,
depending on the animal’s estimated weight) to
each animal about 10 minutes before we started
handling it. Each animal struggled while we
attached the various restraints, but calmed down
quickly thereafter, usually by the time we finished
weighing and taking measurements. All animals
lay still while we attached SLTDRs and took blubber
biopsies; several appeared to sleep through
much of the procedure. Valium greatly reduced
the animals’ struggles to escape, which in turn
reduced the amount of wrestling and fighting
required to restrain them, and reduced total
handling time. Valium undoubtedly minimized
the overall stress experienced by captured animals.
As of 10 April 2000, all eight SLTDRs continue to
transmit data, 36 to 43 days after deployment.
Two of the sea lions have remained within
about 10 km of the capture site. Four others
travelled as far as 30-40 km away from their capture
sites, visiting several haul-out sites. Two
sea lions travelled extensively, paying extended
visits to haulouts 100 km and 110 km from their
capture sites at Aiktak and Long Islands. Results
from analyses of dive data are not available at this
time.
By John Sease.
APIS 2000 Cruise: Multidisciplinary
Research into the Ecology and Behavior of
Antarctic Pack Ice Seals
Background
The research described here was conducted as part of
the Antarctic Pack Ice Seals (APIS) Program, an
international research effort formulated by the SCAR
(Scientific Committee on Antarctic Research) Group
of Specialists on Seals to consider the functional
significance of upper trophic level predators in the
Antarctic pack ice zone and to investigate the
seals’ interactions with their biological and
physical environments. Recognizing the high
cost and logistic difficulties in undertaking
research in the pack ice on a circumpolar scale,
scientists from the United States, Australia,
Germany, South Africa, Norway, and the United
Kingdom collaborated to implement a
multi-disciplinary science program that would be far
greater than the sum of its parts
( Figure 1).
The pack ice region surrounding Antarctica contains
at least 50% of the world’s population of seals,
comprising about 80% of the world’s total pinniped
biomass. As a group, these seals are among the
dominant top predators in Southern Ocean ecosystems,
and the fluctuations in their abundance, growth
patterns, life histories, and behavior provide a
potential source of information about environmental
variability integrated over a wide range of spatial
and temporal scales. Variations in top
predator distribution, abundance, behavior, and
physiology can provide valuable insights into
locations of oceanographic features and areas of
high secondary production.
One of the hypotheses being explored by the APIS
Program suggests that there are measurable physical
and biological features in the Southern Ocean that
result in areas of high biological activity by upper
trophic level predators. Environmental features such
as the margin of the continental shelf, the physical
characteristics of sea ice, ocean fronts, and
icebergs, are thought to produce conditions that
lead to high biomass sites within the pack ice
region. These sites may provide protection
from predators, concentrated prey resources, access
to water for foraging activity, and preferred sites
for animals to give birth or molt. Moreover,
such sites appear to be preferentially chosen
depending upon species’ sex, age, physiological
condition, and general health characteristics.
Preliminary data indicate a strong coupling
between biological characteristics of the upper
trophic level species and the physical features of
the pack ice environment. However, there have
only been rare opportunities to make simultaneous
measurements assessing in detail the processes
leading to high densities of upper trophic level
species associated with such features.
Scientists from the United States took a
multi-disciplinary approach when developing their
contribution to the international APIS Program.
A group of 17 principal investigators from 12
agencies and institutions were funded by the
National Science Foundation’s Office of Polar
Programs to undertake the APIS 2000 cruise, which
focused on the pack ice zone of the Ross Sea. The
total group of 31 scientists that participated in
the APIS 2000 cruise had expertise in seal abundance
and distribution, seal health and nutrition, seal
population genetics and immunogenetics, seabird
ecology, fish and squid ecology, zooplankton and
krill ecology and physiology, sea ice dynamics, and
physical oceanography. The following questions
formed the foundation upon which the APIS 2000
investigators formulated hypotheses within their
respective disciplines:
Within the sea ice zone in the
eastern Ross/western Amundsen Seas in summer —
1. How is the distribution
of upper trophic predators and their prey
influenced by oceanic fronts and ecological
features associated with bathymetry and sea ice?
2. Do biological features
(e.g., prey composition and availability), have a
stronger, direct influence on the distribution of
upper trophic predators than do physical features
(e.g., ice thickness, topography, floe size)?
3. Do upper trophic
predators located in zones where their densities
are relatively high exhibit behavioral and
physiological characteristics that are different
from those of predators in low density areas?
Cruise report
The APIS 2000 cruise departed Lyttleton,
New Zealand, on 20 December 1999 and ended on the
morning of 10 February 2000, when we arrived at
McMurdo Station, Antarctica (Figure
2). The cruise was extremely
productive and allowed us to accomplish a tremendous
amount of research on the ecology and behavior of
Antarctic pack ice seals and their biological and
physical environment. The research vessel N.B.
Palmer proved to be an outstanding platform for
conducting the APIS Program’s multidisciplinary
research. The helicopter detail sailing with
us was also terrific, and the helicopters were a
research tool that we utilized to the fullest extent
that weather allowed. On a typical day, it was
not unusual for our science activities to include
two helicopters aloft flying seal surveys, two or
three Zodiac boats supporting local seal work,
divers, and sea ice sampling, and a CTD cast or HTI
acoustic survey conducted from the ship. Net
tows were conducted in the evening when the seals
went in the water to feed.
A quick look at some summary numbers provides a hint
of the intensity with which the APIS cruise was
conducted: 45 science days, 647 separate science
events, ship track sampling of approximately 800 km
along the Ross Sea polynya marginal ice zone,
nearly 1,000 km along the coastal fast ice, two
short transects across the ice-covered shelf slope
zone, four long transects from the coast to the
northern marginal ice zone (each about 600 km long),
and 175 hours of helicopter flights (which yielded
well over 18,000 km of aerial survey transects for
seals).
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Seals: We had good
success in deploying satellite-linked
transmitters (PTTs) on seals to monitor their
behavior (i.e., distribution, habitat selection,
haul-out behavior, dive behavior). Although
we had been concerned about the potential lack
of molted seals that we might encounter at this
time of year (i.e., early in the molt stage), we
were able to find seals that were in
increasingly advanced stages of molt. Because
the PTTs are fastened to seals’ hair with an
adhesive, it is most desirable to deploy
instruments on seals that have already completed
their annual molt; instruments deployed on
unmolted seals at this time of year are likely
to fall off within a matter of several weeks (in
contrast to remaining active on a molted seal
for several months to one year). We
deployed satellite tags on all four species of
Antarctic pack ice seals: crabeater (22),
Ross (4), Weddell (3), and leopard (2) seals.
We were also very pleased with the
results of our aerial surveys of seal abundance
and distribution, which included good samples of
all the major ecological sampling zones that we
were targeting for the cruise: continental shelf,
shelf slope, interior pack ice, and northern
marginal ice zone. In total, aerial surveys
conducted by the two helicopters staged from the
ship surveyed 18,576 km of pack ice habitat by
air, and observed 11,414 seals (4,817 crabeater,
2,852 Weddell, 79 Ross, 33 leopard, and 3,633
unidentified seals) and 11,066 emperor penguins
With this thorough coverage, we observed an
apparent latitudinal gradient in crabeater seal
density along our four north-south transect lines.
Density was highest in the vicinity of the
shelf and slope (0.75 crabeater seals per square
kilometer) and it decreased exponentially as we
proceeded north over deeper water (0.22 and 0.24
seals per square kilometer in the mid-pack and
northern ice edge, respectively). We
observed a slight increase in crabeater seal
density at the northern ice edge; this higher
density only extended 10-20 km into the pack from
the consolidated ice edge, and may have resulted
from the recent on-ice winds which consolidated
the receding ice in the marginal sea ice zone.
These preliminary results support our
hypotheses that physical fronts associated with
the continental shelf and shelf slope are
important ecological factors influencing the
distribution of crabeater seals. Analyses of
those counts will be enhanced by a superb set of
sea ice data obtained from the belly-mounted
digital video cameras used on all flights.
Samples to evaluate seal condition
and nutrition were taken from 154 seals for blood
analysis (53 Weddell, 58 crabeaters, 40 Ross, and
3 leopard seals) and 157 animals for detailed
morphometric measurements.
More than 1,000 samples were
shipped back to the United States for analysis, in
addition to the analyses conducted on board the
Palmer. Our preliminary data indicate that only
about 10% of the seals had fed within 6 hours of
capture, but only 1 of the 40 Ross seals met this
criteria. This fits with the theory that
Ross seals come to the ice pack for molting, a
time period where most seals limit their feeding
activity. Accordingly, our measurements of
body fat levels are similar to values seen in
other species of seals during the molting period
and are on the lean side. Our ability to
predict seal mass from length and girth
measurements was quite strong, with a better than
0.99 correlation between predicted and actual.
Taken together, these nutritional and body
morphometric data will be combined with analysis
of lipid types in both the seals and their prey
items to construct a model of predator-prey
relationships. Finally, when combined with
the extensive distribution data for seals and
trawling data for prey, we expect to be able to
better model how nutritional status relates to
seal distribution in the pack ice of the Ross Sea.
Biomedical samples were collected
from over 130 seals. Our most complete data
set is for crabeater seals, and we performed
complete medical work-ups on 7-10 crabeaters in
each of the zones sampled on the cruise (pack ice
transects, the northern ice edge, and the southern
polynya/coastal area). We performed 85
microbiological cultures on over 70 animals,
including Salmonella screens, gastrointestinal
tract flora examinations, and skin and wound
cultures. Detailed anesthetic records were
maintained on all seals immobilized during our
handling events, and sera for drug level
determinations will be submitted on a subset of
animals. These data will allow us to
recommend refinements to chemical immobilization
protocols for Antarctic phocids.
A total of 432 samples was
collected for population genetics and
immunogenetics analyses, comprising 181 crabeater
seals, 202 Weddell seals, 42 Ross seals, and 7
leopard seals. Few leopard seals were seen,
as is reflected in the paucity of specimens from
them, while we encountered Ross seals in much
larger numbers than anticipated. Besides
collecting skin samples for genetic analysis, our
observations throughout the cruise gave us new
ideas, perspectives, and insights into some of the
ties between genetic heterozygosity and life
history patterns. For example, crabeater
seals are typically referred to as preferring pack
ice and Weddell seals as preferring the fast ice.
While we found this characterization to be
generally true in the Ross Sea, we found large
numbers of newly weaned pup and subadult crabeater
seals in fast ice areas, in groupings similar to
those we observed in the spring in the Antarctic
Peninsula in the late 1970s, suggesting this
phenomenon may be characteristic of young animals
through more of the year than was previously
thought. Older crabeater seals and fewer
pups were found in the in the interior pack ice
zone. From our preliminary genetic analyses,
crabeater seals appeared to have little or no
development of genetic population
structure,suggesting they move extensively around
the continent and breed in a panmictic fashion.
Thus, it was particularly interesting to
observe that, despite the scarcity of leopard
seals, the scarring rates on crabeater seals was
relatively high, suggesting the animals had
received their wounds elsewhere than in the Ross
Sea area. The tendency for these young seals
to be so abundant in the fast ice could be related
to food availability or to reducing their
vulnerability to predators.
Conversely, we found larger
numbers of Weddell seals than we expected in the
interior pack ice zone, especially subadults and
adults that appeared to have not yet entered the
breeding population. The greatest number of
these animals were found on large floes several
kilomenters across and the seals themselves tended
to be most common away from the edges, and in the
middle of the floes, in habitat with considerable
similarity to land fast ice. However, we are
still puzzled by the predominance of younger, but
apparently nonbreeding, adult Weddell seals in the
land fast ice that were sampled to the east of
Cape Colbeck. Only when we sampled Weddell
seals in the rift cracks approximately 10 km south
into the Ross Ice Shelf from the Bay of
Whales did we find large breeding adult males and
females, suggesting this is a fully established
breeding colony. It is possible that the
Weddell seals we sampled in the pack ice region
originated from regions other than the eastern
Ross Sea coastal area. Our genetic analyses
will facilitate addressing this question since our
analyses to date have shown significant genetic
differences among populations of Weddell seals
from different regions of the Antarctic.
Throughout the interior pack ice
zone in the Ross Sea, we encountered an unusually
large number of Ross seals, usually molting as
single individuals on large floes. It is
likely that the reason we saw so many Ross seals
was that the seals were molting at the time we
were in the pack ice. It has been hypothesized
that they are normally pelagic for much of the
year and, thus, are not usually seen. The
molt of several individuals was characterized by
shedding of large amounts of hair and sloughing of
skin, in a fashion similar to elephant seals.
This observation emphasizes the evolutionary
aspects of the phylogenetic relationships between
the Antarctic ice breeding seals and the elephant
seals and monk seals which we hope to be able to
examine. Our sample of 42 will allow us to
make a statistically significant evaluation of
genetic heterozygosity in this species and to
compare the Ross seals of the eastern Ross Sea
with those near the South African station, from
which we also have a sample, albeit a smaller one.
Finally, from observations made by
other programs on the ship, it appeared that the
benthic community of the shelf region along the
coast had a high biomass of fish and
invertebrates. Although the pathways are not
clear, it seems likely this high biomass and
possibly the particular assemblage of species
there may be partly responsible for the patterns
of distribution of adult and subadult Weddell and
crabeater seals we observed.
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Seabirds: The APIS cruise
made possible the closing of the gap in life
history data for the emperor penguin. We were
able to learn the physical nature of the ice
pack on which they molt, how it declines in area
over the minimum ice month of the year, and the
character of the floes on which they spend the
month molting. We also learned that one of
the preferred areas for molting is
on the fast ice in the shadow of Mt. Siple on
the Marie Byrd Land coast. We were also able to
determine body mass of the birds before and
after the molt, a critical factor in their
survival during this vulnerable period.
Finally, we were also able to gain a
better appreciation of who the emperor
penguin’s neighbors and possible competitors
are during this time in the eastern Ross Sea.
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Fish, squid, and zooplankton:
A total of 19 4-m2 MOCNESS
tows , 22 9-m2 Tucker trawls, 5 15-m
midwater trawl samples, and 6 15-m bottom
tows were taken during the course of the APIS
cruise, encompassing ice edge, deep pack ice,
and shelf-slope environments. Midwater
fauna were sampled in two basic depth strata:
0-500 m and 500-1,000 m. Bottom tows
were executed on the shelf only, in depths
ranging from 250 to 500 m.
Preliminary results from the study
area, based on the general physiognomy of the
trawls, suggest a few trends. First, the
upper 500 m of the water column is nearly devoid
of fishes, except over the shelf. The
typical inhabitants of the midwater, the
lanternfishes, are restricted to depths below 500
m and are very sparse there as well. Euphausiids,
when present, dominate in the upper 200 m. The
major predators captured by our midwater tows were
large jellies such as Periphylla and Stygiomedusa.
The bottom fauna on the shelf, in contrast
to the midwater, was astoundingly rich in both
fish and invertebrate species. Ten-minute
tows produced hundreds of kilos of invertebrate
biomass, and greater than twenty five species of
fishes. Clearly, most of the marine life on
the Ross Sea shelf is on the bottom.
Our preliminary results indicate
that acoustic targets were most prevalent on the
shelf in the coastal polynya, where dense layers
and swarms were detected. Net tows suggested
that these layers were composed primarily of the
euphausiids, Euphausia crystallorophias and
E. superba, and a juvenile fish, Pleuragramma
antarcticum. Layers of euphausiids
and juvenile Pleuragramma also were detected at a
few stations along the ice edge of the Ross Sea
polynya north of the shelf slope. Swarms
were less frequent at stations in the interior and
at the northern edge of the pack ice. In all
regions, acoustic targets occurred primarily in
the upper 100 m of the water column.
Assessments of krill and
zooplankton using divers and net tows went very
smoothly throughout the APIS cruise. We
completed more than 58 dives and 49 net tows in a
variety of coastal and offshore habitats. We
saw a similar pattern for all four long transects,
catching adult and 1-year-old Euphausia superba
at the northern edge of the APIS area and Euphausia
crystallorophias at the southern edge. The
water column in the middle area of transect 4 was
dominated by copepods and krill biomass was at a
low for the transect. Diving observations
correlated well with the net catches with the
exception that the underside of the pack ice seems
the province of 1-year-old and not adult Euphausia
superba. Gravid adults Euphausia
superba have dominated the net catches of
krill along the northern ice edge, making this one
of the richest areas surveyed in terms of energy
available to seals.
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Hydrography and sea ice: For
the hydrography, CTD casts were accomplished
throughout the study area on a spacing of 60 nmi
or less, along with open water stations north
and south of the ice edges on the ends of the
transects. Regular near-surface sampling
was done by the divers using a SeaCat CTD and
under-ice sampling of water for isotopes during
most of the daily dives. An additional
seven ice cores were obtained on the last two
transects at the daily stops and give a roughly
regular grid of sea ice cores across the study
area. On the stop at Bartlett Inlet near
Cape Colbeck, small chunks of green iceberg were
observed, and we sampled three of these pieces
from the Zodiac. Analyses are under way on
ice structure, particulate content, chemical
composition and subsampling for oxygen isotopes.
By John L. Bengtson.
Gray Whale Strandings
In 1999, an unusually high number of gray whales
(273) stranded along the west coast of North America
(see summary
by S. Moore in AFSC Quarterly Report,
October-December 1999), which caused NMFS to consult
the Working Group on Marine Mammal Unusual Mortality
Events in July 1999. The group decided that
this qualified as an unusual mortality event, and an
evaluation was requested. NMFS contracted with
Stephanie Norman to complete this evaluation. The
draft report (Gray Whale Strandings in 1999 and a
Review of Stranding Records in 1995-1998 by
Stephanie A. Norman, Marcia M. Muto, David J. Rugh,
and Sue E. Moore) includes a summary of all
available data; a review of the stranding response;
an assessment of the impact of the mortality event
on the affected population; and a list of potential
causes for the event.
Several factors may have contributed to the high
number of gray whale strandings in 1999:
-
chemical contaminants - overall,
contaminant levels in the whales that stranded
in 1998/99 were not significantly higher than
expected, suggesting that pollution was probably
not the primary cause of death
-
natural toxins - at this time,
there is no definitive evidence that biotoxins
contributed to the increased number of gray
whale strandings
-
disease - although it is
unlikely that all the gray whale mortalities in
1999 were caused by disease, the possibility of
an infectious agent compromising an
individual’s resistance to opportunistic
disease cannot be discounted
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fishery interactions and ship
strikes - only two stranded animals were
entangled in fishing gear and there were no
confirmed ship strikes
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wind and current effects -
variables such as the number of whales passing
through the area, current strength and
direction, and duration of onshore winds
influence the likelihood of a dead whale
reaching the shore and its condition upon
stranding
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starvation - the emaciated
condition reported for some of the stranded
whales supports the speculation that starvation
may be one of several causative factors related
to the observed the primary cause of the
mortalities in 1999; however, there are no data
to support or refute this contention.
Given the expected
natural mortality for a population now estimated in
excess of 26,600 whales, the high number of stranded
animals observed in 1999 most likely did not have a
deleterious effect on the overall population.
By David Rugh and Marcia Muto.
Status of Cook Inlet Beluga Whales
The National Marine Mammal Laboratory (NMML) in
conjunction with other researchers conducting
studies in Cook Inlet, Alaska, is preparing
manuscripts summarizing available information on
beluga whales (Delphinapterus leucas) from
the Cook Inlet stock. Beluga whales occur in
five stocks around Alaska, the most isolated of
which is the Cook Inlet population. The
geographic and genetic segregation of this stock,
combined with their tendency toward site fidelity in
summer, makes this population especially vulnerable
to deleterious impacts from large or persistent
harvests. Results from 6 years (1993-98) of
summer aerial surveys indicated that beluga
distribution within Cook Inlet was shrinking, and
estimated population size has declined by nearly
50%. Point estimates of annual abundance
ranged from 653 whales in 1994 to 347 whales in
1998. This meant that the average reported
harvest of belugas in Cook Inlet during this period
(72 whales) was 21% of the best estimate of
abundance. Relative to the total number of
animals that can be safely removed annually from a
population of marine mammals (referred to as the
Potential Biological Removal (PBR) in the Marine
Mammal Protection Act (MMPA) ), the harvest rate
between 1994 and 1996 was approximately 5 times the
calculated PBR of 14 whales. Notably, the PBR
was later reduced to 1.6 whales when the
calculations incorporated revised abundance
estimates from surveys completed in 1998 and a
revised recovery factor to account for the observed
decline in abundance.
On 19 November 1998, NMFS initiated a formal review
of the status of the Cook Inlet beluga stock through
a cooperative process with the Alaska Beluga Whale
Committee (ABWC) and the Cook Inlet Marine Mammal
Council (CIMMC). The objective of this review
was to provide recommendations to the Alaska
Regional Office and the NMFS Office of Protected
Resources regarding the classification of this stock
as endangered or threatened under the Endangered
Species Act (ESA) or depleted under the MMPA. The
scientific portion of the review focused on the
current status of Cook Inlet belugas: distribution,
abundance, trends in abundance, and habitat. The
effects of the Alaska Native subsistence harvest and
the potential effects of other anthropogenic
impacts, as well as beluga natural mortality were
also examined. Manuscripts covering these
topics will be published in a special issue of
Marine Fisheries Review in summer 2000.
By Sue Moore and Doug DeMaster.
Alaska Eskimo Whaling Commission’s Initial
Mitigation Meeting on Bowhead Whales
On 24 February 2000, NMML held a meeting called
by the Alaska Eskimo Whaling Commission (AEWC) to
discuss concerns about the impacts of oil and gas
development on subsistence use of bowhead whales and
on the communities of the North Slope Borough in
general. Participants included members of the
AEWC, the Barrow Whaling Captains, representatives
from the North Slope Borough, British Petroleum,
ARCO Alaska, Phillips Petroleum, LGL, Clearwater
Environmental, U.S. Minerals Management Service, and
staff from NMFS Headquarters, NMFS’ Alaska Region,
and NMML.
The focus of the meeting was to develop a process
for addressing the following issues:
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1) potential sources of
adverse impacts to bowhead whales and
subsistence hunting
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2) how can threats be
addressed and mitigated
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3) how will impacts,
including cumulative effects, be monitored
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4) establish procedures
for assessing and compensating for any damages
caused by oil development and production.
Preliminary meeting
recommendations included convening interagency
workshops to coordinate agency activities related to
monitoring the impacts of oil and gas development,
clarifying the legislative and administrative
authorities of various agencies with respect to oil
and gas development, and collecting suggestions for
resolving concerns about oil and gas development
from the North Slope Borough communities. A
draft report of the meeting was circulated to
participants in early March, and a final report will
be distributed by late spring 2000.
By Robyn Angliss.
Harbor
Seal Task
The Alaska harbor seal task developed procedures
to digitally grab photographs taken during the
Aleutian Islands assessment survey flown during late
summer 1999. These images were archived on
CD-ROMs, digitally enhanced, and pulled into an
image analysis program. Procedures were
developed to seam overlapping images into one
panoramic image per haulout. Seals were first
counted in all assessment images using the
traditional method of projecting slides onto
counting boards. A sample of these counts was
compared to counts taken using the new digital
method. Initial results indicate that the
digital method is not always a more effective way to
count seals. In particular, images of harbor seals
taken during the Aleutian Island survey typically
showed dark-colored seals on dark wet rocks in
extremely low light conditions; under these
circumstances, the seals in the digitized image were
not any easier to detect, even with a variety of
image enhancement tools available.
However, the technique appears to
work quite well for seals hauling out on other
substrates, such as sand, which provides better
contrast.
Last summer, nine harbor seals associated with the
glacial ice in Tracy Arm, Southeast Alaska were
captured and fitted with time-depth recorders (TDR).
A series of three remote data collection
computers (DCC) were placed in Tracy Arm to monitor
the presence or absence of the tagged seals and to
determine whether individual seals were in the
glacial fjord or in Stephens Passage. In early
2000, programs were written to analyze the DCC data
in preparation for a comparison with the haul-out
and diving behavior data from the TDRs.
By Robyn Angliss.
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