Stock Assessments of the Bottomfish Management Unit Species of Guam, the Commonwealth of the Northern Mariana Islands, and American Samoa, 2019

August 20, 2019

Stock assessments of the bottomfish management unit species (BMUS) for Guam, the Commonwealth of the Northern Mariana Islands (CNMI), and American Samoa were conducted through 2018 and finalized in 2019.

Stock assessments of the bottomfish management unit species (BMUS) for Guam, the Commonwealth of the Northern Mariana Islands (CNMI), and American Samoa were conducted through 2018 and finalized in 2019. Bottomfish resources are managed as one multi-species complex around each territory. The BMUS identified within the archipelagic fishery ecosystem plans (FEPs) is comprised of 16 species for Guam and CNMI and 17 species for American Samoa. These species consist of snappers, groupers, emperors, and jacks.

Several changes relative to previous assessments of BMUS in Guam, CNMI, and American Samoa were incorporated into these 2019 benchmark assessments. These include using new species lists, calculating the percentage of catch reported at the family or species-group level and believed to contain BMUS, filtering CPUE based on gear, standardizing the CPUE for covariates that may affect the catch rate, removing independently-estimated maximum sustainable yield values from the model fitting process, and including a Pella-Tomlinson production model parameterization for Guam and American Samoa.

The assessments used a state-space Bayesian surplus production model within the modeling framework Just Another Bayesian Biomass Assessment (JABBA). Estimates of harvest rate (H), annual biomass (B), the harvest rate associated with overfishing as determined by the harvest control rule (HCR), maximum sustainable yield (MSY), and the biomass at maximum sustainable yield (BMSY) allowed for determination of stock status relative to reference points determining overfishing (H/HCR > 1) and overfished (B < 0.7×BMSY) status. Stock projections were conducted for 2020–2025 for a range of hypothetical 6-year catches, and the corresponding risk of overfishing was calculated.

Stock status of BMUS varied by territory. The current benchmark assessments determined that in 2017, Guam BMUS were in an overfished state but not undergoing overfishing, CNMI BMUS were not overfished nor were undergoing overfishing, and American Samoa BMUS were determined to be both undergoing overfishing and in an overfished state. The status determinations from the 2019 benchmark assessments differed from the previous assessments for Guam and American Samoa, which determined that these stocks were not overfished nor were undergoing overfishing as of 2015.


Langseth B, Syslo J, Yau A, Carvalho F. 2019. Stock assessments of the bottomfish management unit species of Guam, the Commonwealth of the Northern Mariana Islands, and American Samoa, 2019. NOAA Tech Memo. NMFS-PIFSC-86, 177 p. (+ supplement, 165 p.). doi:10.25923/bz8b-ng72.

Last updated on 08/28/2019

Bottomfish