Questions concerning back-calculated abundance apportionment

[brandynlucca]

When back-calculating abundance from the apportioned kriged biomass, it is unclear whether the unaged abundance estimates should be redistributed over the age-bins similar to biomass.

[leewujung]

From meeting with @rebeccathomas-NOAA and @ElizabethMPhillips on 2024/04/16:

For abundance derived from kriged biomass, in the reporting:

• Need global aged and unaged abundance, that is not spatially explicit
• Also need spatially explicit aged + unaged but proportioned to aged summed together

[leewujung]

Some additional digging around in the matlab code:

• These lines get the aged and unaged abundance calculated:
  In get_kriged_biomass.m
  https://github.com/uw-echospace/EchoPro_matlab/blob/main/general/processing/biomass/get_kriged_biomass.m#L342-L352
  No apportioning afterwards to apply the aged proportion to the unaged samples.

• The data matrix is then saved to a different variable name: kriged_Num_Len_Age_Matrix_AcoustM/kriged_Num_Len_Age_Matrix_AcoustF
  https://github.com/uw-echospace/EchoPro_matlab/blob/main/general/processing/biomass/get_kriged_biomass.m#L392-L396

• Then in generate_report.m these variables are used to written to the excel files
  https://github.com/uw-echospace/EchoPro_matlab/blob/main/general/report/generate_reports.m#L106-L116

[leewujung]

Check #219 (comment) for related discussion, for the google slide with flow diagram.

[rebeccathomas-NOAA]

As an FYI, I was investigating some weird abundance results in the full age estimates (age1+ method), and I am pretty sure that the abundance reports are not correct for the age-2+ total number (when age-1's are being included)
If you look at lines
https://github.com/uw-echospace/EchoPro_matlab/blob/553b46b6a8a4c0dae6831727ef9a59a6a0f97b57/general/report/generate_reports.m#L169C1-L170C138
note that the age-2+ total sums all the unaged fish into the age-2+ total, without the age-'1s being apportioned out of the unaged fish.
However, this doesn't throw into question the main matrix, so it is probably a relatively small detail except that these are the exact numbers stock assessors might use in an age-1+ estimate, so I wanted to flag it in case it shows up in EchoPop.