|
Resource
Ecology &
|
Walleye pollock |
7,274 |
|
Sablefish |
471 |
|
Atka mackerel |
1,474 |
|
Pacific whiting |
1,805 |
|
Pacific ocean perch |
986 |
|
Northern rockfish |
493 |
|
Light dusky rockfish |
653 |
Total production
figures were 13,156 with 3,402 test ages and 178
examined and determined to be unageable.
The Alaska Fisheries Science Center again hosted the
biennial CARE (Committee of Age Reading Experts)
Meeting held 6-8 June 2000. The meetings serve
the critical role of allowing all age readers to
communicate their thoughts and techniques on all
aspects related to the ageing of groundfish caught
off the West Coast and Alaska. The meeting’s
theme this year was “Back to Basics,” referring
to going back and comparing estimated ages of
specimens examined under the microscope. A
large number of species including Pacific whiting,
sablefish, thorny head, walleye pollock, black
rockfish, and lingcod were examined.
By Dan Kimura.
STATUS OF STOCKS AND MULTISPECIES ASSESSMENT
PROGRAM
Scientists from the Alaska Fisheries Science Center
attended the Western Groundfish Conference in Sitka,
Alaska, from 24 to 28 April. Members of
the Status of Stocks and Multispecies Assessment
Program attended the conference and gave
presentations dealing with various fisheries topics,
including four presentations related to Atka
mackerel biology and abundance estimation.
Improving abundance estimation of Atka mackerel, by Susanne McDermott, Peter Munro, and Lowell Fritz.
Atka mackerel exhibit aspects of their behavior and biology that make the species difficult to survey with the current standard trawl gear and stratified random sampling design. The intent of this study is to improve the understanding of Atka mackerel distribution patterns and biology and use this knowledge in the design of a species-specific survey for Atka mackerel. Four different estimation approaches were briefly discussed with emphasis on Atka mackerel tagging. This summer a pilot survey was conducted to test the feasibility of tagging Atka mackerel. Preliminary results were discussed and put in context with the goal of improving Atka mackerel survey design.
Atka mackerel fecundity and spawning biology is crucial information needed in designing a spawning survey for Atka mackerel. Atka mackerel are batch spawners with females spawning multiple batches and depositing them in nests guarded by males. This study was conducted to determine batch size, batch number and total fecundity of Atka mackerel. Methodology and results were presented and it was shown how these parameters can then be incorporated into a design of an Atka mackerel spawning survey.
Larval and juvenile Atka mackerel (Pleurogrammus monopterygius) distribution in Alaskan waters: A retrospective study, by Sandra Lowe and Rebecca Reuter.
Atka mackerel are an important forage fish for groundfish, seabirds and marine mammals, including the endangered Steller sea lion. Atka mackerel are an important commercial fishery in Alaska, and comprise the largest groundfish biomass in the Aleutian Islands region. Knowledge of their early life history from egg-larval stages to the juvenile stage is very limited. This study utilizes incidental catch data of Atka mackerel from four historical surveys in areas ranging from Kodiak Island to the western Aleutian Islands to describe the distribution and abundance of juvenile and larval Atka mackerel caught over a 30-year period. Spawn dates back-calculated from larvae lengths suggest that spawning in the Gulf of Alaska occurs during the late summer-early fall. Similar findings were found for the eastern Bering Sea. Increase in the variance of lengths per haul during the spring and winter months in the Gulf of Alaska suggest that optimal spawning conditions can span several months. Juveniles were found in the epipelagic areas of Bower’s and Bering Sea basins during the summer of 1987; this is the first documentation of this behavior in U.S. waters. Juveniles were also found near adult nonspawning habitat in the Aleutian Islands and Gulf of Alaska. Increased knowledge of the larval to prerecruit life history of this species will provide valuable information necessary for the assessment and management of Atka mackerel.
Analysis of Catch-Per-Unit-Effort Data from the Alaskan Atka mackerel (Pleurogrammus monopterygius) fishery: Evidence for localized depletions, by Lowell Fritz and Martin Smith.
Leslie regression
analyses of Atka mackerel fishery catch per unit
effort (CPUE) data collected at 10 fished areas in
the Aleutian Islands region and Gulf of Alaska in
1992-97 revealed significant reductions during the
course of 19 of 39 local fisheries examined.
At a particular area, significant reductions in CPUE
resulted much more often with large removals than
small. Length-frequency distributions and the
time-series of catches and effort suggest that the
exploited populations were not closed in all cases
(e.g., immigration was evident in some), yet the
rates of removal (or emigration) apparently far
exceeded rates of immigration. Examination of the
statistical properties of the data and estimated
regression parameters suggest that while there is
considerable evidence of significant declines in
CPUE, estimates of initial biomass (BO) may not be
unbiased. However, BO estimates from different
years at the same location were similar, suggesting
that the fishery utilizes areas preferred by adult
Atka mackerel, that these areas are replenished over
time, and may have a “carrying capacity”. Temporary
reductions in the sizes of local Atka mackerel
populations could affect other Atka mackerel
predators, such as the Steller sea lion (Eumetopias
jubatus).
By Anne Hollowed.
RESOURCE ECOLOGY AND ECOSYSTEMS MODELING PROGRAM
Stomachs collected totaled 1,828 from the eastern
Bering Sea and 1,090 from the Aleutian Island
region. Laboratory analysis was performed on
672 groundfish stomachs from the eastern Bering Sea,
1,961 from the Gulf of Alaska, and 365 from the west
coast region. Fourteen observers returned 791
eastern Bering Sea groundfish stomach samples (580
Pacific cod, 211 arrowtooth flounder) during the
quarter.
By Patricia Livingston.