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Stock assessment updates of the bottomfish management unit species of American Samoa, the Commonwealth of the Northern Mariana Islands, and Guam in 2015 using data through 2013
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2016
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[PDF-1.52 MB]
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Description:In this report, we conduct a strict stock assessment update of the Bottomfish Management Unit Species (BMUS) complexes in American Samoa, the Commonwealth of the Northern Mariana Islands, and Guam, using the same base case production model as used in the previous stock assessment (Brodziak et al., 2012), but with an additional 3 years of catch and nominal catch-per-unit-effort (CPUE) as input data. A Bayesian statistical framework is applied to estimate parameters of a Schaefer production model fit to a time series of annual nominal CPUE statistics to provide direct estimates of parameter uncertainty for status determination. The surplus production model is a state-space model, including both process error in biomass production dynamics and observation error in the catch-per-unit effort data. Overall, the American Samoa, the Commonwealth of the Northern Mariana Islands, and the Guam bottomfish complexes were not overfished (overfished is defined as B <0.7*BMSY) and were not experiencing overfishing (overfishing is defined as H> HMSY) in 2013, the most recent year of the stock assessment estimates. We conducted stock projections for 2016 and 2017, which projected a range of hypothetical two-year catches and calculated corresponding future risks of overfishing. For the American Samoa BMUS complex, the 2017 catch level that would produce a 50% risk of overfishing in 2017 was 115 thousand pounds. For the Commonwealth of the Northern Mariana Islands BMUS complex, the 2017 catch level that would produce a 50% risk of overfishing in 2017 was 250 thousand pounds. For the Guam BMUS complex, the 2017 catch level that would produce a 50% risk of overfishing in 2017 was 71 thousand pounds. All of these catch values associated with a 50% risk of overfishing in 2017 are much higher than actual bottomfish landings in 2013 for American Samoa, the Commonwealth of the Northern Mariana Islands, and Guam which were approximately 24 thousand, 23 thousand, and 30 thousand pounds, respectively. [doi:10.7289/V5PR7T0G (http://dx.doi.org/10.7289/V5PR7T0G)].
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Rights Information:CC0 Public Domain
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