Midwater Assessment: Bering Sea
Scientists from the Midwater Assessment and Conservation Engineering (MACE)
Program conducted an echo integration-trawl (EIT) survey of the southeastern
Bering Sea shelf and Bogoslof Island region from 18 February to 10 March
2002. The survey was designed to provide data on the abundance
and biological composition of walleye pollock in the Steller sea lion Conservation
Area (SCA) and the portion of the Central Bering Sea Convention Specific
Area close to the Aleutian Islands, between Unalaska Island and the Islands
of Four Mountains.
Survey operations were conducted 24 hours a day. The acoustic systems
were calibrated at the start and end of the survey. A total of 27 trawls
hauls were made with a midwater trawl (Aleutian wing trawl) and 11 were
made with a poly Nor-eastern bottom trawl.
Preliminary survey results show that pollock were most abundant inside
the eastern portion of the SCA (Figure 5 above ), an area with high commercial
catches. Pollock modal lengths were about 49 cm near Amak Island and decreased
gradually towards the west and north. On the northern and western part
of the SCA along the 200 m isobath, age-2 pollock with modal lengths 22-24
cm were abundant. This year class had been observed as age-1 pollock during
the 2001 winter survey. In the Bogoslof area, pollock were concentrated
in two main locations: between Umnak and Unalaska Islands and in Samalga
Pass adjacent to the Islands of Four Mountains. The size distribution
was generally bimodal, with 47 cm fish predominating in the Umnak area,
and about 57-60 cm pollock predominating in the Samalga Pass area. Presence
of the 47 cm pollock size class in the Bogoslof area suggests that a younger
year class (1995 or 1996) may have recruited to the Bogoslof pre-spawning
population. Pollock biomass in the Bogoslof area was about the same as
that observed during the 2001 survey.
Ancillary research projects conducted during the survey included: pollock
ovary collections to determine fecundity , whole fish collection, spawning
mature pollock and culture of fertilized eggs, collection of pollock fin
clips for analysis of DNA markers, and whole stomach collections. At the
start of the cruise, the NOAA ship Miller Freeman and the Japan Fisheries
Agency ship Kaiyo Maru conducted an intership calibration in the Islands
of Four Mountains area. After the intership calibration, scientists aboard
the Kaiyo Maru conducted an EIT survey of shelf/basin waters near the Aleutian
Island Chain between 170°W and 176°W longitude.
By Taina Honkalehto.
Fisheries Oceanography Coordinated Investigations (FOCI):
Arrowtooth Flounder Survey
Morgan Busby, Debbie Blood, Rachael Cartwright, Bill Floering, Ann Matarese,
Jim Stark, and Duane Stevenson participated in the 2002 arrowtooth flounder
spawning survey aboard the NOAA ship Miller Freeman 3-9 February in the
Gulf of Alaska. As was observed in last years survey, males and females
were segregated by depth indicating that peak spawning had not yet begun.
Bottom trawls conducted at 200 and 400 m depths on the outer shelf and
upper slope west of Kodiak Island were dominated by females with most mature
and running ripe individuals occurring at 400 m. Tows conducted at 500
and 600 m depths contained nearly all males with numerous ripe individuals
found at 500 m. Toward the end of the cruise in the area off the Shumagin
Islands, eggs stripped from two ripe females collected at 400 m and held
in a live well were successfully fertilized with milt from males collected
at 500 m. On the last trawl of the cruise, eggs stripped from a single
ripe female collected at 500 m were fertilized with milt from several males
from the same haul.
The ripe female was the only female collected in the tow. The fertilized
eggs were brought back to Seattle for incubation in the FOCI Rearing Laboratory
at Sand Point
By Morgan Busby.
quarterly Jan-March 2002 sidebar
Auke Bay Lab