JFM 2001 Quarterly Rpt. sidebar
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(Quarterly
Report for Jan-Feb-Mar 2001)
Figure 1. The relative abundance of pollock on
the eastern Bering Sea shelf and in the Bogoslof
Island region as determined from
hydroacoustic data collected 19 February - 11 March
2001.
Midwater
Assessment & Conservation Engineering:
Eastern Bering Sea and Bogoslof Island Survey
Scientists from the Midwater Assessment and
Conservation Engineering (MACE) Program conducted an
echo integration-trawl survey of the Southeastern
Bering Sea Shelf and Bogoslof Island region from 19
February to 11 March 2001 (Figure 1 above).
The survey was designed to provide data on the
abundance and biological composition (size and age)
of walleye pollock in the Steller sea lion
Conservation Area (SCA) and the portion of the
Central Bering Sea Convention Area close to the
Aleutian Islands, between Akutan Island and the
Islands of Four Mountains. The data will aid
in managing and assessing the impact of commercial
fisheries on Steller sea lions and their habitat.
Survey operations were conducted 24 h per day.
The acoustic systems were calibrated between
the shelf and Bogoslof legs of the survey. A
total of 32 trawls were made with the standard
Aleutian wing trawl and 3 were made with an 83-112
bottom trawl.
Preliminary survey results show that pollock were
most abundant at the eastern edge of the SCA (Figure
1 above), an area with high commercial catches.
Pollock were on average about 45 cm in length
in this area, and very few pollock smaller than 30
cm were observed here. On the northern and
western part of the SCA, age-1 pollock with lengths
10-15 cm were abundant. Age-1 pollock were not
abundant in the SCA in previous winter surveys. In
the Bogoslof area, pollock were concentrated in two
locations: between Umnak and Unalaska Islands and in
Samalga Pass. The size distribution was as in
previous years, with mean lengths about 60 cm,
indicating that the population has not been renewed
by the appearance of new, strong year classes.
Pollock biomass was substantially reduced from
that observed in the 2000 survey.
Ancillary research projects conducted during the
survey included: pollock ovary collections for
fecundity determination, whole fish collection,
spawning mature pollock and culture of fertilized
eggs, analysis of DNA markers for pollock fin clips,
and whole stomach collections. A Korean
scientist, Mr. Hyun-Su Jo, was aboard for both legs
of the cruise.
By Paul Walline.
Gulf of Alaska Survey
MACE scientists conducted an echo integration-trawl
survey of the Shumagin Islands area 12-19 February.
Survey operations were conducted 24 hours per
day. Ten trawls were made with an Aleutian
wing trawl (AWT) and 7 were made with a Poly Nor’eastern
(PNE) bottom trawl. Pollock were present in
most of the surveyed area, with adults generally
distributed near Renshaw and Swedania Points
(typically within 50 m of the bottom), and 2-year
olds generally distributed in West Nagai Strait and
Shumagin Gully. Two-year old pollock also
often formed a well-defined layer at depths between
about 150-180 m depth. Eulachon (Thaleichthys
pacificus) were present in most of the areas
surveyed (4% by weight, 30% by number). Nearly
45% of the adult pollock (i.e., greater than 35 cm
fork length) were either in a “spawning” or “spent”
stage of maturity. This suggests that the time
of peak spawning was a little earlier than that
observed during the last formal survey of this area,
which occurred 14-20 February 1995, when about 6% of
the fish were classified as spawning or spent.
MACE scientists conducted echo integration-trawl
surveys of the Shelikof Strait area and east Kodiak
Island from 13 to 27 March. The Shelikof Strait
portion of the survey, which was conducted 13-18
March between Chirikof Island and Cape Chiniak, was
the 19th spawning stock survey of pollock in
Shelikof Strait since 1980. (No surveys were
conducted in 1982 and 1999.) Transect spacing was
7.5 nmi. A total of 15 AWT and 4 PNE hauls
were conducted during this portion of the survey.
Unlike most previous years, relatively few
mature prespawners were found in the Shelikof Strait
sea valley on the west side of the strait (Katmai
Bay to Cape Nukshak). The pollock distribution
was similar to the 1988 survey, when a relatively
greater amount of pollock were found on the east
side of the strait rather than on the west side.
Significant quantities of juvenile pollock
(primarily age-2) were observed from about Chirikof
Island to Cape Kerkurnoi, including a well-defined
midwater layer of primarily age-2 pollock at about
160-180 m depth. Few age-1 pollock were
present in the Shelikof Strait. Survey timing
was appropriate based on time of peak spawning.
For example, maturity comparisons were similar
to previous years. For females greater than 40
cm, 73% were mature prespawning, 1% were spawning,
and 2% were spent. A second pass of the strait
occurred 23-26 March at 15 nmi spacing. Three
transects in the southern strait were dropped
because of bad weather. Two AWT and 5 PNE
hauls were conducted during the second pass.
No changes in pollock distribution or length
or maturity composition were generally observed
between the two passes.
Chiniak and Barnabas Gullies were surveyed 19-23
March to assess the distribution of pollock off the
east side of Kodiak Island. Three AWT hauls were
conducted in Chiniak Gully, and three AWT and one
PNE haul were conducted in Barnabas Gully. Virtually
no pollock were detected in either gully. The
small amount of pollock echosign that was
detected was attributed primarily to either 1- or
2-year olds. Juvenile pollock size
compositions varied slightly among the few hauls
that were conducted in both gullies (e.g., 1-year
olds throughout Barnabas and near the head of
Chiniak gully; 2-year olds nearer shelf break in
Chiniak and absent in Barnabas). Whether these
trends in catch data represent “typical”
winter-spring distribution patterns will require
further research.
Ancillary research projects for the Gulf of Alaska
surveys included pollock ovary collections for
fecundity determination, whole fish collections for
sea lion and seabird diet studies, whole juvenile
pollock collections for studies on the winter check
on juvenile pollock otoliths and on seasonal effects
on juvenile pollock diet and condition, spawning
mature pollock and culture of fertilized eggs,
analysis of DNA markers from pollock fin clips to
examine genetic population structures, and whole
stomach collections for food habits analyses.
By Mike Guttormsen.
Fisheries-Oceanography
Coordinated Investigations (FOCI)
Scientists of the RACE Division and visiting
scientist Fumihito Muto (Hokkaido University,
Laboratory of Marine Biodiversity, Japan)
participated on cruise MF01-01 aboard the NOAA ship Miller
Freeman from 28 January to 5 February. The
primary objective of the cruise was to conduct
bottom trawl sampling on the outer continental shelf
and upper slope in the Gulf of Alaska to collect
ripe adult arrowtooth flounder and deploy deep bongo
plankton tows to collect their eggs. This work
was needed to establish the appearance of arrowtooth
flounder eggs so they can be identified with
confidence in plankton samples. Twenty four
stations were occupied. Operations included
recovery and deployment of an oceanographic mooring
for the Center’s Kodiak Laboratory, CTD casts,
60-cm bongo tows, and Nor’eastern bottom trawls.
On 2 February, eggs stripped from a ripe female
arrowtooth flounder were successfully fertilized
with milt collected from three ripe males.
After the cruise, the eggs were transported to
the AFSC Seattle facilities where they completed
development and began hatching 24 February.
Yolk-sac larvae are currently being sampled to
document development of pigmentation.
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