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NOAA Technical Memorandum NMFS-AFSC-281

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Deployment performance review of the 2013 North Pacific Groundfish and Halibut Observer Program

Abstract

As part of a new annual review process implemented by the North Pacific Fishery Management Council for the North Pacific Groundfish and Halibut Observer Program, the Observer Science Committee used a set of performance metrics to assess the efficiency and effectiveness of observer deployment into the trip- and vessel-selection categories of the partially observed fleet. These included deployment rate metrics that evaluated whether achieved sample rates were consistent with intended sample rates, sample frame metrics that quantify differences between the population for which estimates are being made and the sample from which those estimates are derived, and sample size analysis to determine whether sample rates were high enough to ensure adequate spatial and temporal coverage. Evaluation of the deployment performance was conducted at the stratum level. Each stratum is defined by the sampling unit (i.e., vessels or trips) and/or the rate of sampling.

There was a marked different in the relative performance of the two deployment methods in 2013. In trip-selection, sample rates were adjusted from 0.15 to 0.11 during a part of the year to avoid cost overages and then returned to the original rate. This created three temporal strata within the trip-selection stratum. Realized rates of coverage for 2013 met the anticipated coverage goals for all trip-selection strata, the Observer Declare and Deploy System performed as expected throughout the year and was unaffected by the government shutdown in October. Excepting small deviations at the start and end of the year, there was no evidence of bias present in the temporal or spatial analyses conducted in trip-selection, and observed and unobserved trips had similar characteristics.

In the vessel-selection stratum, coverage levels were less than expected during the first five selection periods (January - October). The random selection of vessels for observer coverage was abandoned during the last selection period (November-December). During this selection period coverage levels achieved the anticipated number of vessels specified in the 2013 Annual Deployment Plan. Coverage shortages in vessel-selection were due to a lack of a proper sampling frame and a substantial non-response (17-71% among selection periods). The small number of observed trips in each selection period made distinguishing differences in trip attributes between observed and unobserved portions of the fleet difficult. With this caveat in mind, large differences in trip duration or landed catch weight were not evident. Observed trips did tend to have landings with higher diversity in landed catch than unobserved trips.

Some expected patterns were found in both deployment methods; Reporting Areas and gear types that had more fishing effort had higher probabilities of having observer data in that gear/area/stratum combination. There were differences in the probability of an observed trip between gear types, with trawl generally having a higher probability of observation due to concentrated fishing in fewer areas (e.g., more trips in any given area) whereas hook-and-line was more disperse (e.g., fewer trips in an area) and more areas/stratum combinations had a higher probability of zero observer coverage.

An examination of observed and unobserved tender and non-tender trips did not yield meaningful differences, but the number of observed tender trips was too low to examine on a fine temporal or spatial scale.
Coverage rates for dockside sampling did not meet the objective of deploying observers to complete salmon sampling during all pollock offloads in the Gulf of Alaska for the purpose of obtaining genetic tissues used to identify stock of origin (91% were observed).


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