[Feature]: Movement is fxn of mean length-at-age

[k-doering-NOAA]

Imported from redmine, Issue #68519
Opened by @RickMethot on 2019-09-12
Status when imported: New

Consider making a new movement option that is a fxn of mean length-at-age. Then with platoons, the larger platoon would have advanced movement.

[Rick-Methot-NOAA]

current code is in get_migration(), a copy of this has already been created as get_migration2(), so let's experiment there.

code does a linear interpolation based on age:
// SS_Label_Info_20.1.1 #age-specific movement strength based on parameters for selected area pairs
temp = 1. / (move_def2(k, 6) - move_def2(k, 5));
temp1 = temp * (move2 - move1);
migrrate(yz, k) = move1 + (r_ages - move_def2(k, 5)) * temp1;
migrrate(yz, k)(0, move_def2(k, 5)) = move1;
migrrate(yz, k)(move_def2(k, 5), nages) = move2;
migrrate(yz, k) = mfexp(migrrate(yz, k));
Ip += 2;

to create the new option, replace move_def2(k, 6) and move_def2(k, 5), which have units of integer age, with the mean fish length at that age.

PROBLEM:
we also want to have sex-specific movement per #60 , which will affect how migrrate is indexed and stored.

Also if we want movement to be responsive to growth, then it need to be stored according to each "g" platoon.