JAS 2000 Quarterly Rpt. sidebar
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(Quarterly
Report for July-Aug-Sept 2000)
Cooperative
Research: Whale Survey off Brazil
Waters off the
northeastern coast of Brazil were a major whaling
ground during the 20th century until 1985. After
whaling ended, little information was available
about the status and possible recovery of whale
stocks there. To determine the status of
the whale populations off the northeastern
coast of Brazil, the Brazilian Environmental Agency
(IBAMA), with support from the Brazilian Navy and
the National Council for Science and Technology
(CNPq), sponsored cetacean sighting cruises in the
former whaling ground in 1998, 1999, and again in
2000. This year a scientist from the National
Marine Mammal Laboratory (NMML) participated in the
2000 cetacean survey, as the first step in
establishing a long-term cooperative research
project between the United States and Brazil.
The survey was conducted from 14 August to 5
September 2000 aboard the Brazilian Navy ship Almirante
Graca Aranha and consisted of two 10-day legs,
with a 3-day break between legs. The primary
objective for the first leg was to conduct a line
transect survey for Antarctic minke whales (Balaenoptera
bonaerensis) in offshore waters of Brazil from
approximately lat. 5°S to 10°S , offshore to
approximately long. 33°W. The primary
objective for the second leg was to conduct a line-transect
survey for humpback whales (Megaptera
novaeangliae) in shelf waters from approximately
5°S to 13°S. All other cetacean species were
recorded.
The Almirante Graca Aranha is a 74-m long
vessel, and the survey was conducted from the 12- m
high flying bridge with four observer stations while
the ship was at a speed of approximately 9 kt.
One observer searched from the bow to 90° off
the starboard side of the ship, while another
searched from the bow to 90° off the port side.
They searched mostly by naked eye with occasional
sweeps with Fujinon 7x50 hand-held binoculars.
The other two observers searched the trackline
from 0° to 10° (one to starboard and one to port),
alternating every 5 minutes between naked eye and
binoculars. For every sighting, a distance
measurement (using reticles in the binoculars) and
an angle (using a pelorus) was recorded. A
data recorder recorded the beginning and end times
of survey effort, environmental conditions, and
sighting information. The observers rotated
positions every half hour resulting in a 2.5-hour
shift followed by a 2-hour rest period. The
survey was suspended during inclement weather and
when light levels were too low for efficient
observations.
A total of 1,071.1 nautical miles (nmi) were
surveyed: training: 90 nmi; Leg 1: 490.9 nmi;
Leg 2: 490.2 nmi. Sightings included 209 cetacean
groups. The most frequent species were
humpback whales (107 sightings), bottlenose dolphins
(Tursiops truncatus) (35 sightings),
pantropical spotted dolphins (Stenella attenuata)
(11 sightings), and Antarctic minke whales (9
sightings). Additional species sighted included
clymene dolphins (Stenella clymene) (2
sightings), sei whales (Balaenoptera borealis)
(2 sightings), tucuxi (Sotalia fluviatilis)
(3 sightings), spinner dolphins (Stenella
longirostris), (1 sighting, mixed with
pantropical spotted dolphins), and 1 dwarf minke
whale (Balaenoptera acutorostrata). Unusual
sightings included 1 group of 8 false killer whales (Pseudorca
crassidens), a pair of pygmy killer whales (Feresa
attenuata) with bottlenose dolphins, a mother
and calf Cuvier’s beaked whale (Ziphius
cavirostris), a multispecies aggregation of 6
Antarctic minke whales, 10 shortfinned pilot whales
(Globicephala macrorhynchus) and 40
bottlenose dolphins.
Results from this survey will be combined with
previous years’ survey results to produce
abundance estimates for minke and humpback whales
and to report other new information about cetacean
species in Brazilian waters. The IBAMA plans
to conduct three additional surveys from 2001 to
2003. The major goal is to expand the survey area
and attain abundance estimates of minke whales from
5°S to 25°S. They also plan to collect biopsy
samples from all cetacean species, whenever
possible, and develop an acoustic project for large
whales. A cooperative effort will continue with NOAA
and Brazilian scientists.
By Janice Waite and Alexandre Zerbini (School of
Aquatic and Fishery Sciences, University of
Washington)
Aerial Surveys and Radio Tagging of Harbor
Seals in Bristol Bay
Harbor seals (Phoca
vitulina), were surveyed along the coast of
Bristol Bay, Alaska, and adjacent waters from about
Goodnews Bay in the north, to Unimak Pass in the
south. This region is one of five that are
surveyed on a 5-year rotation to estimate the
range-wide abundance of harbor seals in Alaska.
An additional survey was conducted along the
southern Alaska Peninsula from Unimak Pass to
Chignik, part of the very large Gulf of Alaska
region, the remainder of which will be surveyed in
2001. The surveys were conducted on 12-29
August by six observers flying in five chartered
aircraft. Observers flew daily survey routes
to obtain counts (or photographs to be counted
later) on as many as 9 days at each site where
harbor seals hauled out. These daily
replicates provide information required to adjust
for conditions such as date, time of day, tide
height, and weather, which influence the proportion
of seals ashore during the surveys. This was
the first systematic survey of harbor seals in
southwestern Bristol Bay, which included Izembek
Lagoon National Wildlife Refuge. Although seal
numbers were expected, based on anecdotal reports,
to be low in this area, we found the opposite to be
true, with several groups of 300-500 seals observed
daily on sandbars near breaks in the lagoon barrier.
To estimate the total abundance of harbor seals, the
proportion of seals that were missed because they
were not ashore during surveys must be obtained by
other means, such as a mark-resight estimate. In
collaboration with the U.S. Fish and Wildlife
Service (USFWS), harbor seals were tagged with radio
transmitters during early August in Nanvak Bay in
the Togiak National Wildlife Refuge. This site
in northwestern Bristol Bay was selected because
seals are typically abundant there and because of
the opportunity for logistical cooperation with the
USFWS. From 5 to 16 August 2000, three to six
seals were captured daily at low tide with tangle
nets in a procedure similar to one used for harbor
seals hauled out on ice (AFSC
Quarterly Report October-November-December 1999).
Thirty-two seals were captured, measured,
weighed, tissue-sampled for genetic analysis, and
tagged with single radio transmitters on a rear
flipper so that the radio signal could be detected
only if the seal was ashore. During
aerial survey flights in the Nanvak Bay area, the
presence and location of radio-tagged seals were
recorded. Most tagged seals remained in Nanvak
Bay, but on some days up to half were resighted
outside the bay up to 50 km away. These
resighting data, along with other data obtained from
a receiver and data-logger installed in the study
area, will be used to derive a correction factor for
the proportion of seals missed during the aerial
surveys.
By John Jansen, Dave Withrow, and Peter Boveng.
Alaska Harbor Seal Comanagement Workshop
Four NMML scientists
participated in a Harbor Seal Comanagement Workshop,
held on 25-26 September 2000, in Juneau, Alaska.
The workshop brought together scientists,
hunters, elders, and other technical experts in the
areas of population monitoring, harvest management,
and education, to provide perspectives on the
current state of knowledge in those subject areas
and to identify critical needs for information in
support of harbor seal conservation. A half day was
dedicated to a discussion on each subject area. Dave
Withrow gave a presentation on the NMML research
program for monitoring harbor seal populations.
Following the workshop, the Harbor Seal
Comanagement Committee, composed of three members
each from the Alaska Native Harbor Seal Commission
(ANHSC) and NMFS, drafted its first action plan.
According to the Comanagement Agreement
between the ANHSC and NMFS, the action plan,
which is to be updated annually, will be the guiding
document for joint and separate management actions
by the ANHSC and NMFS related to the conservation
and management of subsistence use of harbor seals.
By John Bengtson and Peter Boveng.
Pinniped Population Studies at San Miguel
Island
National Marine
Mammal Laboratory scientists conducted pinniped
population studies at San Miguel Island, California,
from 18 May through 9 August 2000. The primary
focus of the studies was to continue the long-term
study of survival, recruitment, natality, health,
and population trends of California sea lions (Zalophus
californianus), and northern fur seals (Callorhinus
ursinus). Research activities included
observation of branded sea lions and tagged fur
seals, pup mortality surveys, and live pup counts of
both species. During the mortality surveys at
the end of July, scientists necropsied sea lion and
fur seal pups to assess the incidence of hookworm
infestation and to study the genetics of two
different species of hookworms that affect these
pinnipeds.
In general, California sea lion and northern fur
seal pup production increased in 2000. Sea
lion pup production increased 3%, and northern fur
seal pup production increased 52 % from 1999.
California sea lion production appears to have
recovered from the severe decline in 1998; however,
northern fur seal production still remains 46% below
the 1997 estimate, indicating that the 1997-98 El Niño
event has had a long-term impact on northern fur
seals at San Miguel Island. Mortality surveys
for California sea lion pups indicate an increase in
pup mortality from 14% in 1999 to 19% in 2000, but
northern fur seal pup mortality declined from 26% in
1999 to 10 % in 2000. All 30 California sea
lion pups and 20 northern fur seal pups sampled for
hookworms had severe infestations, which probably
caused their deaths. Long-term monitoring of the
health of these two populations indicates that
hookworm infestations have become a significant
cause of mortality in the past decade.
The brand-resighting effort produced 7,300 sightings
of 1,674 branded individual sea lions, including
414 branded females with pups and 19 territorial
males. Increased effort to sight tagged
northern fur seals produced sightings of 142
individuals. These data will be used to
generate age-specific survival and natality
estimates for these species at San Miguel Island for
use in age-structured population models. The
results of the 2000 field season show the importance
of continued monitoring of the sea lions and fur
seals at San Miguel Island. Such data will
provide a unique opportunity to identify the roles
that disease and the environment play in the
population dynamics of these two species.
By Sharon Melin.
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