Developing a gillnet based abundance-at-age index for 4RSw Atlantic herring / by Mélanie Santo, Elisabeth Van Beveren and Kim Émond.: Fs97-6/3733E-PDF

"In 2021, a new experimental gillnet survey was started in Northwest Atlantic Fisheries Organization (NAFO) divisions 4Sw and 4R in collaboration with local harvesters, with the goal of developing a new index of spring and fall spawning Atlantic herring (Clupea harengus). This document outlines the survey design, proposes an analytical approach for estimating abundance-at-age indices, and provides an initial assessment of index quality. A new gillnet selectivity model was developed to convert observed length-specific catch rates across multiple mesh sizes into stock abundance-at-length, which was transformed into abundance-at-age using age-length keys. The resulting age compositions successfully tracked dominant cohorts, appeared robust against sample variability in space and time, and aligned with other independent data sources. While the indices appear promising for informing age composition, estimates of overall abundance remain uncertain in part due to limited time series lengths. Additional years of data will help with index validation and clarify its role in future assessments"--Abstract, page iv.

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