250
12. Kelp, Urchins, and Otters in the California Coastal Region
INIT Urchins_2125
600000 {urchin}
INFLOWS :
to_2125
OUTFLOWS :
(IN SECTOR: Urchins 1620)
die5 = (Urchins_2125*nat_death_rate) +number2125eaten
{urchin/month}
to_2630 = (Urchins_2125- die5) /tto5 {urchin/month}
ave_wt5 = 0.00549 {kg /urchin}
kg2125eaten = if Biomass_30p1us > = Kg_Urchin_consumed
then re1_dens5*Kg_Urchin_consumed else total_wt5 {kg}
number2125eaten = kg2125eaten /ave_wt5 {urchin}
rel_dens5 = if total_wt5 and Biomass_30plus >0 then
(total_wt5 /Biomass_30plus) else 0 {unitless}
total_wt5 = ave_wt5*Urchins_2125 {kg}
tto5 = 12 {month}
Urchins 2630
dead6{t) = dead6{t-dt) + (die6) * dt
INIT dead6 = 0 {urchin}
INFLOWS:
die6 = (Urchins_2630*nat_death_rate) +
number2630eaten{urchin /month}
Urchins_2630{t) = Urchins_2630{t-dt) + (to_2630-die6to_3135) * dt
INIT Urchins_2630 = 250000 {urchin}
INFLOWS :
to_2630
OUTFLOWS:
(IN SECTOR: Urchins 2125)
die6 = (Urchins_2630*nat_death_rate) +
number2630eaten{urchin /month}
to_3135 = (Urchins_2630-die6) /tto6 {urchin/month}
ave_wt6 = 0 .00964 {kg /urchin}
kg2630eaten = if Biomass_30plus > = Kg_Urchin_consumed
then rel_dens6*Kg_Urchin_consumed else total_wt6 {kg}
number2630eaten = kg2630eaten /ave_wt6 {urchin}
rel_dens6 = if total_wt6 and Biomass_30plus >0 then
(total_wt6 /Biomass_30plus) else 0 {unitless}
total_wt6 = ave_wt6*Urchins_2630 {kg}
tto6 = 11 {month}