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OPC California MPA project

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biomass calculation

brunj7 opened this issue · comments

commented

Goal: Compute biomass estimates from fish length

Data conversion

We have several main cases:

  • We have the total length (TL):
    • We have the right unit for a and b: g and cm => done
    • We have the wrong units for a and b => need to transform using formulas
  • We have another type of length:
    • We need to first transform the length into the total one using the formula in column "LL_Equation_for_WL"

Main formula: W = a * L^b

Unit transformation (source: Fishbase)

a'(cm, g) = a (mm, g)*10^b
a'(cm, g) = a (cm, kg)*1000
a'(cm, g) = a (mm, mg)*10^b/1000
a'(cm, g) = a (mm, kg)10^b1000

Relationship reference: https://www.fishbase.de/manual/fishbasethe_length_weight_table.htm

code: https://github.com/NCEAS/ca-mpa/blob/main/analyses/1performance_eco/code/biomass_reference_file_prep.R