Jackknife recruitment
A new recruitment options has been added (for use initially in the north sea model).
Equations used
if SSB < B then R = jack_a * SSB
if SSB >= B then R = jack_a * jack_B
with R = recruitment in numbers of individuals
SSB = total biomass of spawners in [g] wet weight
jack_a is the slope (usually set as initial biomass of recruits / SSB)
jack_B is an empirical proxy for a relationship with the carrying capacity (in the north sea they used 0.3 * long term average total biomass).
Using the new option
In the biol.prm files you will need to add the following parameters for each age structured group (zero entries fine if the option is off). To turn the option on set flagrecruit to 15
Jack-Knife recruitment
jack_a_XX 0 Slope in Jack-knife for XX
jack_b_FPL 0 Carrying capacity proxy in Jack-knife for XX