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Alternative sampling designs for the 2017 annual deployment plan of the North Pacific Observer Program
  • Published Date:
    2016
Filetype[PDF - 866.49 KB]


Details:
  • DOI:
    doi:10.7289/V5/TM-AFSC-338
  • Corporate Authors:
    Alaska Fisheries Science Center (U.S.)
  • Series:
    NOAA technical memorandum NMFS-AFSC ; 338
  • Document Type:
  • Description:
    Changes in regulation enacted in 2013 have enabled the Alaska Fisheries Science Center's Fishery Monitoring and Analysis Division (FMA) and the Alaska Regional Office's Sustainable Fisheries Division to work collaboratively on an Annual Deployment Plan (ADP). Each ADP documents how the National Marine Fisheries Service (NMFS) plans to deploy observers into fishing activities for the coming year under the limits of available funding. Draft ADPs are presented to the North Pacific Fishery Management Council (Council) during September - October and are finalized in December. The sampling design for observer deployment has two elements: how the population is subdivided (i.e., stratification schemes) and how available samples are allocated (i.e., allocation strategies). Here the relative performance of four alternative sampling designs (at the primary sampling unitthe trip) are compared in support of the 2017 draft ADP. Each alternative design has different strata configurations and optimizes the allocation weighting of samples (observed trips) in each stratum based on the number of trips, the variance of groundfish catch, and the cost of observing a trip. Total sample size is determined by the available budget and the cost of observing each trip during the calendar year. Resulting coverage rates are presented for optimal allocations based on only retained catch, only discarded catch, and a compromise blend of retained and discarded catch. Gap analyses that examine the chance of at least one or three observed trips in a NMFS Area × Gear type combination were used as a performance metric. Total sample size (trips observed) is expected to be reduced by nearly a third due to a halt in Federal funding. Gap analyses illustrated that stratifications based on gear type (3 strata) or gear type × tendering activity (6 strata) outperform stratifications that include a separate strata comprised of five vessels that act as both catcher processors and catcher vessels and fish using hook-and-line gear (i.e., partial CP HAL strata). However, these partial CP HAL vessels disproportionately fish in Aleutian Island NMFS Areas that have been problematic for obtaining observer coverage in the past. All sampling designs were forwarded to the Council for consideration during their October 2016 meeting in recognition of 1) the tradeoff between obtaining data from a small subset of vessels in the Aleutian Islands at the cost of increasing the number of cells with a high chance of zero coverage elsewhere, and 2) all the designs examined here are variants of the best performing design considered for the 2016 ADP. Of these, the NMFS recommended - and the Council approved - that the 6 strata design with optimal sample allocations based on discarded groundfish catch be used for the 2017 ADP. [doi:10.7289/V5/TM-AFSC-338 (http://dx.doi.org/10.7289/V5/TM-AFSC-338)]

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