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Subsampling catches to determine sex-specific length frequency in Alaska Fisheries Science Center bottom trawl surveys
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2023
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[PDF-5.31 MB]
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Description:Length frequency sub-samples are collected to provide sex-specific length composition data for groundfish stock assessments during the Alaska Fisheries Science Center bottom trawl surveys. The overall workload on board of survey vessels, which included determining sex for each individual in the length frequency sub-samples (e.g., upwards of 200 per haul per species), has likely led to unacceptable numbers of acute and repetitive stress injuries of survey staff. In December 2021, a working group was formed to evaluate the effect of reducing length frequency sub-sample sizes for which sex is determined on length composition uncertainty. Over the spring of 2022, the working group developed a bootstrap-simulation approach that determines changes in uncertainty for reduced sub-sample sizes. For the majority of species limiting sub-samples to 100 fish per haul reduces length composition input sample sizes by ≤ 25% from status quo length composition input sample sizes. Therefore, upon meeting with stock assessment authors the joint recommendation between the working group and assessment authors to the survey staff was to limit length frequency sub-sampling for sex determination to 100 subsampled fish per haul.
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Rights Information:CC0 Public Domain
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