Female sablefish age-at-maturity in Alaska applicable to stock assessment
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Female sablefish age-at-maturity in Alaska applicable to stock assessment

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    This report is a summary of results from sablefish maturity studies conducted in December 2011, July through August 2015, and December 2015. More thorough investigations and descriptions of these studies have been published or are in preparation for publication. Included here are descriptions of ovarian development, definitions used for microscopic and macroscopic maturity classification, and age-at-maturity results that may be applicable to sablefish stock assessment in Alaska. In winter 2011 and 2015, microscopic methods were used to categorize maturity. In summer 2015, maturity was classified three ways: macroscopically atsea by several scientists, macroscopically from photographs by a single expert observer (standardized macroscopic), and microscopically (with histology slides). Macroscopic methods, used during the summer, resulted in estimates of the age-at-50% maturity (A50) that were younger than histological and standardized macroscopic methods. Because the macroscopic method could not be validated by the microscopic method, classifications made at-sea may not accurately represent the current oocyte development. For the summer months, oocytes were in later stages of development in the second half of August and so this time period provides the most accurate predictions whether fish will spawn in the coming season. December proved to be an ideal time to sample for maturity because fish that would spawn were in advanced stages of vitellogenesis. In winter 2011, skipped spawning was more prevalent than in the summer or winter of 2015. For the 2011 samples, incorporating skip spawning into age-at-maturity models had a large effect on age-at-maturity. [doi:10.7289/V5AFSC-PR-2017-12 (https://doi.org/10.7289/V5/AFSC-PR-2017-12)]
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