12.5. Questions and Tasks
251
Urchins 313 5
dead7(t) = dead7(t-dt) + (die7) * dt
INIT dead7 = 0 {urchin}
INFLOWS:
die7 = (Urchins_3135*nat_death_rate) + number3135eaten
{urchin /month}
Urchins_3135(t) = Urchins_3135 (t-dt) + (to_3135-die7to_3640) * dt
INIT Urchins_3135 = 150000 {urchin}
INFLOWS:
to_3135
OUTFLOWS:
(IN SECTOR: Urchins 2630)
die7 = (Urchins_3135*nat_death_rate) + number3135eaten
{urchin /month}
to_3640 = (Urchins_3135-die7) /tto_7 {urchin /month}
avewt7 = 0.01542 {kg /urchin}
kg3135eaten = if Biomass_30p1us > = Kg_Urchin_consumed
then rel_dens7*Kg_Urchin_consumed else total_wt7 {kg}
number3135eaten = kg3135eaten /avewt7 {urchin}
rel_dens7 = if total_wt7 and Biomass_30plus >0 then
(total_wt7/Biomass_30plus) else 0 {unitless}
total_wt7 = avewt7*Urchins 3135 {kg}
tto_7 = 18 {month}
Urchins 4145
Dead_9(t) = Dead_9(t-dt) + (die_9) * dt
INIT Dead_9 = 0 {urchin}
INFLOWS:
die_9 = (nat_death_rate*Urchins_4145) + number4145eaten
{urchin /month}
Urchins_4145(t) = Urchins_4145 (t-dt) + (to_4145to_4650-die_9) * dt
INIT Urchins_4145 = 150000 {urchin}
INFLOWS:
to_4145
OUTFLOWS:
(IN SECTOR: Urchin3640)
to_4650 = (Urchins_4145-die_9) /tto_9 {urchin /month}
die_9 = (nat_death_rate*Urchins_4145) + number4145eaten
{urchin /month}