is the seasonal time step equal to 0.25 years. Equation is used for determining for all () from (0,2) to (12,4), except for () = (12,1) where Equation applies. This allows for fish aged 12 or older still surviving at the end of season 4 to be included in next season-1’s age-12 cohort for accounting purposes, in addition to the standard flow of fish aged 11 at the end of season 4.
are the corresponding RHS 
for all (
) from (0,2) to (12,4), except for (
.