28 Groundfish Port Availability
Description We estimated the relative availability of groundfish biomass to individual ports following the methods described in Selden et al. (2020), with some exceptions. In brief, we used data from the Northwest Fisheries Science Center’s West Coast Groundfish Bottom Trawl Survey (Keller, Wallace, and Methot 2017) to estimate spatial distribution of species-specific biomass (Location Biomass), and the Center of Gravity (CoG) of the Location Biomass. We then calculate the Availability Index for each port by summing the Location Biomass within a radius from that port based on the 75th quantile of the distance traveled from port to harvest of species of interest, weighted by catch, as measured from trawl logbooks. We analyzed 12 species that make up a large component of landings for vessels using bottom trawl gear along the West Coast, or that have broader management interest (e.g., shortbelly rockfish).
The present analysis differs from Selden et al. (2020) in three ways:
1- We estimated the spatial distribution of species using the R package sdmTMB (Anderson et al. 2022) instead of VAST (Thorson 2019). The sdmTMB models included Pass and normalized depth as fixed parameters. Year was a time variable and models included both spatial and spatiotemporal (iid) autocorrelation, and a delta-poisson-link-gamma error distribution (Thorson 2018).
2- We used the Location Biomass directly instead of scaling it by spawning stock biomass from the assessment. Thus, the Availability Index is a relative biomass index and not actual available biomass. Biomass was then scaled to 0-1 for presentation by dividing by the highest value in any year.
3- We used only the WCGBTS, and did not combine the Triennial survey (1980-2004) with the WCGBTS. This approach shortens the analysis period but allows us to expand the depth range to 55-1250 m.
2025-01 Update Previous sdmTMB models used a delta-poisson-link-gamma model structure/distribution and included depth a linear factor. In 2025 (for the CY2025 ESR), models were updated to use a delta-lognormal model structure, and normalized depth was included as a smoothed variable (with three knots). The delta-lognormal models produced better residuals (as evaluate with QQ-plots) than the delta-poisson-link-gamma models. The smoothed depth term allowed non-linear relationships with depth, such as higher mid-depth abundance versus shallow and deeper zones.
Indicator Category Ecological Integrity
Data Steward N. Tolimieri, NMFS/NWFSC (nick.tolimieri at noaa.gov)
Additional Information Data are collected and analyzed independently by N. Tolimieri, who submits unpublished figures and plots to the CCIEA editorial team.
Data sources Data for indicators come from the West Coast Groundfish Bottom Trawl Survey (WCGBTS) (Keller, Wallace, and Methot 2017) for 2003-2021. There were no data for 2020 because the WCGBTS was canceled due to the COVID-19 pandemic. The survey data includes estimates of age, length, and biomass for subsamples of each haul, and occasionally for the entire haul when catch is low.
References