Executive Summary Summary of Changes in Assessment Inputs

• Main Authors: Martin Dorn, Kerim Aydin, Steven Barbeaux, Darin Jones, Kally Spalinger, Wayne Palsson
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Gulf of Alaska; alaska pollock; Alaska
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.302.9719; http://www.afsc.noaa.gov/REFM/Docs/2012/GOApollock.pdf

3. ADFG crab/groundfish trawl survey: 2012 biomass and length composition. 4. The pre-1984 trawl survey data were removed from the model. 5. The egg production index (1981-1992) was removed from the model. Changes in assessment methodology Based on recommendations of the July 2012 CIE review of the Gulf of Alaska pollock assessment, several changes in the assessment model are considered. The goal in this assessment was to implement recommendations that could be relatively easily accommodated within the existing model framework, and to postpone to future assessments those recommendations that require methodological development and substantial analysis. The following changes were implemented: 1) the model includes ages 1-10 rather than ages 2-10 as in previous assessments; 2) an accumulator age was added to initial age composition and stronger equilibrium assumptions were used to initialize the model; 3) mean unbiased log-normal likelihoods are used for survey biomass indices; 4) the historical trawl data (pre-1984) was removed from the model; 5) the egg production index (1981-1992) was removed from the model; 6) six selectivity blocks were used for fishery selectivity rather than allowing selectivity parameters to vary annually with a random walk; 7) reduced weights (input sample sizes) were used for the fishery age composition data; and