Initialisation Relative biomass

Relative biomass

Another method to initialise Osmose is to use relative biomass. This method is called if population.initialization.relativebiomass.enabled is enabled. With this method, the user specifies, for each species:

• population.initialization.biomass.sp#: the initialisation biomass for each species ($B_s$, float)
• population.initialization.size.sp#: the size-boundaries (float[]). Size is $N_{class} + 1$
• population.initialization.tl.sp#: the trophic level for each size-class (float[], size $N_{class}$)
• population.initialization.relativebiomass.sp#: the proportion of total biomass to attribute to each size-class ($P_{s, k}$, float[], size $N_{class}$, $\in[0, 1]$)
• population.initialization.age.sp#: the age to attribute to each size-class (float[], size $N_{class}$)
• population.initialization.nschool.sp#: the number of schools to create for each size-class ($N_{s, k}``int[]$)

Using all these parameters, schools for a given species are initialised as follows.

• For each size-class, biomass to release is computed by multiplying the input biomass by the relative proportion: $B_{s, k} = B_s \times P_{s, k}$.
• Loop over the number of schools to create.....
• Randomly select a length between the lower and upper size-bounds of the given class. If age is 0, force length to be equal to species eggSize.
• Using length, weight is compued using an allometric relationship. If age is 0, force weight to be equal to species eggWeight.
• Compute the number of individuals to put in school $i$: $A_{s, k, i} = \dfrac{B_{s, k} \times 10^6}{N_{s, k} \times W_{s, k, i}}$

The steps are summarised below:

graph TD;

    id0("Reading parameters") --> id1
    id1("Loop over species") --> id2("Loop over size-class")
    id2 --> id3("Compute relative biomass")
    id3 --> id4("Loop over number of schools")
    id4 --> id5("Random draft of length")
    id5 --> id6("Create school")
    id6 --> id4
    id6 --> id2
    id6 --> id1

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