Northwest Fisheries Science Center

Fisheries Observation Science Topics

Staff

Jon McVeigh
Program Manager
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Data Processing

WCGOP data processing includes these steps:

  1. Expand the subsample of species composition to the tow/set-level.
  2. Translate observer species codes to the appropriate fish ticket data codes used in the Pacific Fisheries Information Network (PacFIN) database.
  3. Identify and select observer data records to match to fish tickets.
  4. Query and process all PacFIN fish ticket data.
  5. Merge observer data and fish ticket data.
  6. Remove data deemed inappropriate for subsequent use.

A tow/set-level expansion is needed to estimate the total retained and discarded weight for each spe-cies because the sampling procedure used to collect species composition data allows for subsampling. The following equation is used to calculate the weight of the subsample by summing across the observed weights of the individual species:

where:

xks= observed weight of the species s in catch category k in the subsample

wk = weight of the subsample from catch category k

The sampling ratio (Rk) used to scale the subsample weights to the amount in the catch category is calculated by dividing the weight of the subsample by the total weight of the catch category using the equation:

where:

yk = the total weight of catch category k

The tow/set-level expanded weight of species s in category k is calculated by dividing the species weight in the subsample by the sampling ratio in the following equation:

where:

Xks= the weight of species s in catch category k

Tallying the weight (Xks) of the species (s) across all categories (k) within a tow/set provides the total weight of the species retained or discarded.

The retained catch records from the observer data are merged with fish ticket data to provide more accurate estimates of retained catch. WCGOP data are linked to fish tickets by direct fish ticket number(s) obtained by the observer and/or by comparing the return date recorded by the observer with the dates of fish tickets from the vessel. For trips with multiple fish tickets, the fish ticket data are combined for analysis purposes. For trips with missing fish tickets, the observer retained catch data are not adjusted. The translation of WCGOP to PacFIN species codes allows a more seamless match of observer data with fish ticket data and provides consistent information for calculations.

For the fish ticket matching process, observer data that meet the following criteria are removed:

Next, the translation step adds coding to the WCGOP observer data that allows for the appropriate match to the The next link/button will exit from NWFSC web site coding system used in PacFIN.

The WCGOP data are adjusted so that the total trip pounds of retained fish in a catch category matches the total trip pounds on the fish ticket because the fish ticket weight is often more accurate and fish tickets are legally binding documents. To match the total trip pounds, the weights within each observer retained catch category are scaled up or down by the ratio of fish ticket and observer trip weights for that category, using the following equation to calculate the adjustment factor:

where:

xmtk = lbs in catch category k in tow/set t in trip m

Amtk = adjustment factor used for catch category k in tow/set t in trip m

The equation used to adjust the WCGOP data is:

where:

C mk = lbs in catch category k for trip m recorded on the fish ticket

When a catch category in the WCGOP data cannot be matched to a fish ticket catch category, the WCGOP data are not adjusted. Catch categories found only on the fish tickets are distributed across the observed tows/sets using the proportion of the observed catch per tow/set divided by the total observed catch per trip using the following equation:

where:

Bmt= the proportion of observed catch in tow/set t in trip m

Cmtk = lbs in catch category k for tow/set t in trip m recorded on the fish ticket

After the observer data are merged and adjusted to fish ticket data, any data removed during the matching process are then incorporated back into the matched data file.

Prior to subsequent use of the observer data, data that meet the following criteria are removed:

WCGOP Data Processing Appendix and Links

This appendix table provides species identification codes used in the Pacific Fisheries Information Network (PacFIN) database and assigned to WCGOP observer data, with identification of aggregated species groups used in reporting of the groundfish fishery.

Year of data Year of release Format
20162017 tables (excel)
20152016 tables (excel)
20142015 tables (excel)
20132014 tables (excel)
20122013 tables (excel)
20112012 tables (excel)
20102011 tables (excel)

PacFIN (Pacific Coast Fisheries Information Network) Data Processing Appendix and Links

This appendix outlines the protocol through which PacFin data is processed in order for fishery scientists to estimate annual catch by sector and total groundfish mortality.

Year of release Format
2017 PDF

For a description of the Pacific Fisheries Information Network (PacFIN) database, visit the The next link/button will exit from NWFSC web site Pacific States Marine Fisheries Commission’s website.

For a list of all species managed under the Pacific Coast Groundfish Fishery Management Plan (FMP), visit the The next link/button will exit from NWFSC web site Pacific Fishery Mangement Council’s website.