In NOAA-EDAB/neusCatch: Multispecies length expansion of commercial catch

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The following set of rules are the basis for mscatch.

In many stock assessments each year may result in a different level of aggregation (i.e quarters, semesters or different gear types).

Note: minimum number of length samples ~ 1 per 200 metric tonnes landed. (unwritten rule of thumb, check )

(Within each year, t)

Combine:

• Are there gear types with total landings greater than 0 but total sample sizes less than X?

    + if YES: Combine gear types (explore to see if combined lengths similar) 
    to increase sample size or Ignore and continue (add to total at the end).
    + if NO: Count your blessings and continue.  

• Are there market categories (they are not on ordinal scale) with total landings greater than 0 but sample sizes less than X? (after combining gears).

      + if YES: combine market categories with similar length distributions. 
      + if NO : Count your blessings and continue.  

• Are there quarters with landings but sample sizes less than X?

    + if YES: Create semesters?  (Currently semesters are skipped and jump straight to annual)
      + if NO: Count your blessings and continue.  

• Are there strata with landings but sample sizes less than X?

      + If YES: define groups of similar strata  
      + If NO: Count your blessings and continue.  

• Interpolate remaining holes.

      + Select length within year/market category from adjacent strata or strata group
      (after determining if appropriate).  
      + Select length within year/market category from adjacent quarter or semester
      (after determining if appropriate).  
      + Select length within year/market category from adjacent year
      (after determining if appropriate).  

• If unclassified market category and no other information available:

      + Combine market category samples to create an unclassified  
      + Use appropriate observer length samples to apply to unclassified. 

• If holes remain

      + Calculate ratio of sampled to un-sampled landings and expand
      total length frequency such that expanded sample weight equals
      total landings weight for year t.

Interpolate only:

If examination of sample matrix shows only sporadic missing cells with landings but sample sizes less than X:

• Samples by year/gear/quarter/stat area/market category

  • Nearest stat area within market category/quarter/gear/year
    • Keeping year/market category constant:
      • Adjacent quarter/ same stat area
        • Adjacent quarter/ any stat area within ecoregion
          • Adjacent semester/matching stat area
            • Adjacent semester/ any stat area within ecoregion
              • If lengths by gear are similar: Alternative gear/same quarter/stat area
                • Alternative gear/same quarter/any stat area
                  • Alternative gear/semester/same stat area
                    • Alternative gear/semester/any stat area
                      • No options- extrapolate to total

Or combination of both approaches

NOAA-EDAB/neusCatch documentation built on Jan. 23, 2025, 3:29 a.m.