Entering the sampling of landings from a haul in SS and SA table: 2 alternatives possible?

[nmprista]

In an onboard trip, one samples landings and discards. Landings are sampled by size category. Discards sampled by taking 3 baskets. Baskets are pooled together before sorting.

The way I interpret the design is that the haul is stratified into landings and discards. Then:

• landings are stratified into species. And species further stratified into size categories. Samples are then taken from each size category.
• discards are sampled (baskets). Then baskets are stratified by species. And a sample taken from each species.

I see two possibilities to declare this design with regards to the landings component and wonder which one is better

• declare a landings row only in the SS table -- SA table starts directly with species landed with stratification ==Y --- size categories are children of species rows, with stratification == Y

• declare a landings row in SS table and in the SA table -- SA table starts with a landings row with stratification == N --- species are children of that landings row, with stratification==Y --- size categories are children of species rows, with stratification == Y

Seems to me that alternative 2 is more explicit and also allows the entering of total weight of landings while alternative 1 does not. But it is also more complex involving similar work to the discard case.

a FAQ might be needed if one of the alternatives is found to allow for correct estimation. Specific code for estimating both alternatives might need to be considered if both are considered to work and choice is left to the user.

[HenrikK-N]

This will be discussed at the WKRDB-EST2.

[davidcurrie2001]

The other alternative is that you declare a landings row in the SS table, and then just have an SA row for each combination of species and size category, with no sub-samples e.g. if you have sampled unsorted cod, and 3 size categories of haddock then you would just have 4 SA rows (COD unsorted, HAD size 1, HAD size 2, HAD size 3).

[HenrikK-N]

WKRDB-EST2 conclude that for now all 3 options (2 options and an alternative) are valid, option 1 is preferred. Declare a landings row only in the SS table -- SA table starts directly with species landed with stratification ==Y --- size categories are children of species rows, with stratification == Y

[nmprista]

Analysis done at WKRDB-EST2: WKRDBEST2_Annex5_Issue5_SA_Table.docx

[lizclarke]

The Estimation subgroup concluded on 07/09/2021 that we agree with the WKRDB-EST2 analysis that alternative 1 is the best option for the most common sampling situation. We propose to add alternative 1 to the guidance and explain the situation when it applies, and reference WKRDB-EST report for a more detailed explanation. We will remove the "unsampled other" category from the example.

[lizclarke]

The Estimation subgroup revisited on 16/03/2022. We think the documentation requires a longer section on the SA table, also as a result of including bycatch data. To be discussed in plenary.