The 2002 GOA pollock assessment was updated by incorporating new catch,
age composition, biomass estimates, and maturity data into the assessment.
The 2002 EIT trawl survey of the Shumagin Islands provided a biomass estimate
of 135,600 t. The 2002 Shelikof Strait biomass estimate of age-2+ fish
was 229,100 t, a decrease of 38% from the 2001 biomass estimate. The biomass
of adult fish in Shelikof Strait (38,037 t) was lower than expected. An
additional 82,100 t of pollock were encountered along the shelf break during
exploratory transects. The ADF&G trawl survey biomass estimate was 96,237
t, an 11% increase from the 2001 biomass estimate. Evidence from these
surveys indicates that the 1999 year class will be above average.
GOA Pacific Cod
The 2002 Pacific cod assessment incorporated several new types of data
including size composition from 2001 and January-August 2002 commercial
fisheries and catch from the 2001 fisheries.
The flatfish group is subdivided into deep-water flatfish, rex sole, shallow-water
flatfish, and flathead sole. The projected 2003 exploitable biomass for
each category is based on a delay difference model that includes estimates
of growth, natural mortality, and recruitment, as well as biomass estimates
from the 1996 and 2001 bottom trawl surveys. ABC and OFL were calculated
by species, with individual species identified as Tier 4, 5, or 6 depending
upon the available data. The 2001 GOA bottom trawl survey biomass was
used as the current biomass for calculation of ABC for deep water, shallow
water and rex sole. An age-structured model was used to estimate ABCs
for flathead sole (see table 1. above).
GOA Arrowtooth Flounder
The 2002 stock assessment for arrowtooth flounder was updated with new
catch information. An age-structured model developed with AD Model Builder
software was utilized for this assessment. Similar to the previous assessment,
the model accommodated a higher proportion of females in the larger size
intervals of both survey and fishery data by giving males a higher natural
mortality rate than females.
In 2002, the thornyhead assessment was updated with 2001 harvest levels
by gear and relative population numbers from the 2002 sablefish longline
survey. Alternate models examined assumptions regarding natural mortality
and length at age. The author recommended ABC, OFL, and spawning stock
biomass levels were 2,555 t, 3,051 t, and 23,549 t, respectively. The
Plan Team recommended an ABC of 2000 t to compensate for uncertainty in
the natural mortality estimate.
Auke Bay Lab