2016 Assessment of the Atka Mackerel Stock in the Bering Sea and Aleutian Islands
February 12, 2016
From the December 2015 SSC minutes: The SSC reminds the authors and PTs to follow the model numbering scheme adopted at the December 2014 meeting. The Atka mackerel assessment follows the model numbering scheme (Option D) as described in the most recent version of the SAFE Guidelines.
The SSC encourages the authors and PTs to refer to the forthcoming CAPAM data-weighting workshop report. The authors will refer to the Special Issue on Data Weighting in Fisheries Research and explore alternative data weighting methods for the 2017 Atka mackerel assessment. An initial first step was to rescale the sample sizes specified for fishery and survey age composition data. Sample sizes were scaled to have the same mean as in the baseline model (Model 14.1), but varied relative to the number of hauls sampled (see Model Structure section).
The SSC recommends that assessment authors work with AFSC’s survey program scientist to develop some objective criteria to inform the best approaches for calculating Q with respect to information provided by previous survey trawl performance studies (e.g. Somerton and Munro 2001), and fish-temperature relationships which may impact Q. The authors discuss the potential effect of temperature on survey catchability and fish behavior in the Survey Data section. The variation in survey biomass and low survey abundance estimates for Atka mackerel in 2000 and 2012 may be associated with colder than average temperatures in the region and their effects on fish behavior. We will continue to examine survey and temperature data and work with the AFSC survey program to understand whether temperature affects the vertical or broad scale distribution of Atka mackerel to make them less available to the trawl during cold years.