Hi Giancarlo,
Thanks for the question. One way I think you could try is to create a model with multiple growth patterns (also called growth morphs) or possibly platoons.
Here is the definition of growth morphs from the SS user manual:
Number (N) of growth patterns (GP), also referred to as morphs:
These are collections of fish with unique biological characteristics (growth,
mortality,weight-length, reproduction). The GP x Sex x Settlement Events
constitute unique growth patterns that are tracked in SS. They are assigned
these characteristics at birth and retain them throughout their lifetime. At
recruitment, growth pattern members are distributed across areas (if any)
and they retain their biological characteristics even if they move to another
area in which a different cohort with different biological characteristics
might predominate. For example, one could assign a fast-growing growth
pattern to recruit predominately in a southern areas and a slow-growing
growth pattern to a northern area. The natural mortality and growth
parameters are specified for each growth pattern in the mortality-growth
parameter section in the order of females growth pattern 1 to growth
pattern N followed by males growth pattern 1 to growth pattern N in a
two sex model.
However, I can see how this approach could get too complex if you wanted to do this for each cohort in the model. Perhaps there is a simpler way that I am not aware of?
Hope this helps get you started, at least.
Cheers,
Kathryn
