STATUS OF STOCKS AND MULTISPECIES ASSESSMENT PROGRAM:
2002 Stock Assessment Summary
The Status of Stocks and Multispecies Assessment Program (SSMA) completed
stock assessments for major groundfish stocks in the Bering Sea, Aleutian
Islands, and Gulf of Alaska. (The information provided in this report
summarizes the 2002 stock assesments. Complete
assessments are available from the Status of Stocks and Multispecies Assessment
Program's website.) Information from a variety of sources were
used including survey biomass estimates provided by the RACE Division,
fishery catch estimates from the NMFS Alaska Regional Office, fishery dependent
biological samples from the REFM Observer Program and fishery and survey
age composition data from the REFM Age and Growth Program. Final SAFE
(Stock Assessment and Fishery Evaluation) reports were prepared for the
North Pacific Fishery Management Council (NPFMC) meetings. The NPFMC used
the assessments to recommend levels of Acceptable Biological Catch (ABC)
for the 2003 fishing season.
Scientists from the SSMA Program participated in preparation of many of
the assessment chapters for the Gulf of Alaska and Bering Sea/Aleutian
Islands regions. Scientists from the Auke Bay Laboratory, the RACE Division,
and the Alaska Department of Fish and Game also authored or contributed
to the development of the SAFE chapters.
In 2002, 15 stocks or stock complexes in the Bering Sea/Aleutian Islands
(BSAI) were assessed: walleye pollock, Pacific cod, yellowfin sole, Greenland
turbot, rock sole, flathead sole, arrowtooth flounder, Alaska plaice, other
flatfish (includes 16 species of flatfish), BSAI Pacific ocean perch, other
red rockfish, other rockfish, sablefish, Atka mackerel, and "other species"
(see Table 1 below for species included in stock complexes). With the exception
of sablefish, SSMA stock assessment authors were lead authors for all BSAI
assessments. In the Gulf of Alaska (GOA), 10 stocks or stock complexes
were assessed: walleye pollock, Pacific cod, arrowtooth flounder, other
flatfish, Pelagic shelf rockfish, slope rockfish, demersal shelf rockfish,
thornyhead, sablefish, and Atka mackerel. SSMA authors were the primary
authors on 8 of the 10 GOA assessment chapters. Major findings for selected
assessments are summarized below, grouped by management area and species.
Table 1. Species categories established for
management of the Bering Sea/Aleutian Islands groundfish fishery.
Pacific ocean perch
Other red rockfish
a Species which must be returned to the sea when caught.
b Species for which an individual TAC is established.
c Species for which an aggregate TAC is established.
A nonspecified species category was also established to cover all species
not listed above.
The values presented below reflect information found in the SAFE documents
developed by the NPFMC's Plan Teams for groundfish fisheries in the GOA
and BSAI. It should be noted that the Plan Team ABC and Total Allowable
Catch (TAC) recommendations are reviewed by the NPFMC advisory bodies and
the Council recommends the final TAC. Thus, the values presented below
may differ from the final Council recommendations. For information final
groundfish specifications, please consult the NPFMC's web page at
BSAI Walleye Pollock
This year's walleye pollock assessment features new data from the 2002
bottom trawl survey, the 2002 echo-integration trawl (EIT) survey and from
the 2001 fishery. The 2002 bottom trawl survey estimated a biomass of
4,820,000 metric tons (t). The 2002 EIT survey estimated biomass was 3,600,000
t. Pollock otoliths collected during the bottom trawl survey were examined
for age determination, and numbers-at-age from this survey were estimated
and used in the stock assessment. Length frequency data from the EIT survey
were applied to an age-length key constructed from the bottom- trawl survey
data to derive a preliminary age composition for that survey. Pollock
age and size composition data were used to estimate the 2001 catch-at-age.
Estimates of weight-at-age for 2001 were also added to the assessment.
In previous years, the SSC determined that reliable estimates of
the probability density function for FMSY
exist for this stock, and that eastern Bering Sea (EBS) walleye pollock therefore qualified for management
under Tier 1. The maximum permissible value of fishing mortality
under Tier 1a is based on the harmonic mean value of FMSY.
This translates into a 2003 catch of 2,327,000 t. Under Tier 1a, the 2003 overfishing
level is 3,532,000 t corresponding to a fishing mortality rate of
The authors noted that a fixed catch of 1,400,000 t would maintain the
stock above B40%
level of spawning in the near term and greatly reduced future yield variability.
The 2002 bottom trawl survey of the AI region resulted in a biomass estimate
of 175,283 t, an increase from the previous estimate from the 2000 survey.
Aleutian and Bogoslof Islands pollock qualify for management under Tier
5. For the AI region, this gives an ABC and Over Fishing Level (OFL) of
39,438 t and 52,585 t, respectively. For Bogoslof Island pollock, the
2002 EIT survey of the region resulted in a biomass estimate of 227,000
t. The adjusted value (considering that this region is treated as an index
site for the Bering Sea basin or Donut Hole stock) for ABC is 4,074 t.
BSAI Pacific Cod
The 2002 assessment updated last year's assessment, incorporating new catch
and survey information. This year's EBS bottom trawl survey resulted in
a biomass estimate of 616,923 t, a 26% decrease from last year's estimate.
The Aleutian Islands were surveyed in 2002; the biomass estimate was 82,853 t,
representing a decrease of 39% from the 2000 estimate. The 2003 estimate
of Pacific cod age 3+ abundance was 1,680,000 t. Projected 2003 spawning
biomass for the BSAI stock was 423,000 t, essentially unchanged from last
year's estimate for 2002. The SSC has determined that reliable estimates
exist for this stock, and that this stock therefore
qualifies for management under Tier 3 of the BSAI Groundfish Fishery Management
Plan (FMP). The recommended 2003 ABC and OFL for the BSAI stock was 245,000
and 324,000 t, respectively.The Bayesian meta-analysis, which has formed
the basis for a risk-averse ABC recommendation in each of the 1996-99 assessments,
was not performed for the present assessment. The ratio between the recommended
given in the 1999 assessment (0.87) was assumed to be an
appropriate factor by which to multiply the 2003 maximum permissible
to obtain a recommended 2003
The recommended OFL was determined from the Tier 3 formula times 0.87. Model projections indicate that this
stock is neither overfished nor approaching an overfished condition.
An alternative model configuration with a separate set of selectivity schedules
for year 2000 and beyond was evaluated in the 2002 assessment.
quarterly Oct-Dec 2002 sidebar
Auke Bay Lab