Report of the Benchmark Workshop on Pelagic Stocks (WKPELA). 17–21 February 2014 Copenhagen, Denmark

• Main Author: ICES
• Format: Text
• Language: English
• Published: 2014
• Subjects: geo; envir; Petersen; Northeast Atlantic
• Online Access: https://archimer.ifremer.fr/doc/00222/33350/31751.pdf; https://archimer.ifremer.fr/doc/00222/33350/

WKPELA meeting was held in ICES HQ in Copenhagen from the 21–27 February 2014, to benchmark the assessments of herring in the Celtic Sea and mackerel in the Northeast Atlantic. The data compilation process and intercessional work began in October 2013. The assessment of both of these stocks was previously done using a statistical catch-at-age model ICA, which imposed structural assumptions on the data; the validity of some of these assumptions had been questioned in recent years. In the case of NEA mackerel the previous assessment was not considered to give a reliable estimate of the development of the stock, and this assessment was limited by the lack of independent age-structured indices. New data which was examined for mackerel included fishery-independent data (acoustic surveys, bottom-trawl surveys, and a swept-area trawl survey), as well as a re-examination of the tagging data, landings and discard and biological data. For NEA mackerel the benchmark workshop agreed updates to the input data on catch, weight-at-age, maturity ogive, and changes to the estimation methods for other assessment parameters such as proportion of F and M before spawning. There was also an agreement to include age-structured indices on adults (from the IESSNS swept-area trawl survey) and recruits (IBTS Q4 trawl survey), and to use the tagging data as an index of population abundance-at-age using a Petersen estimator. The IESSNS survey was proposed to be included in the assessment as an abundance index at age, although it was also suggested as a research need, to investigate its use as an index of relative proportions at age only (i.e. without the trend in abundance). The tagging index was considered to give useful information on population abundance at up to 2007, around which time the methodologies changed and the recapture rates dropped inexplicably. There is a research recommendation to investigate the changes in the tagging methodologies (both release and recapture), with a view to updating the tagging dataseries when the ...