252
12. Kelp, Urchins, and Otters in the California Coastal Region
avgwt_9 = 0 .03287 {kg /urchin}
kg4145eaten = if Biomass_30plus > = Kg_Urchin_consumed
then rel_dens9*Kg_Urchin_consumed else total_wt9 {kg}
number4145eaten = kg4145eaten/avgwt_9 {urchin}
rel_dens9 = if total_wt9 and Biomass_30plus > 0 then
(total_wt9/Biomass_30plus) else 0 {unitless}
total_wt9 = Urchins_4145*avgwt_9 {kg}
tto_9 = 31 {month}
Urchins 4650
Dead_10(t) = Dead_10(t-dt) + (die_10) * dt
INIT Dead_10 = 0 {urchin}
INFLOWS:
die_10 = (nat_death_rate*Urchins_4650) +
number4650eaten {urchin/month}
Urchins_4650(t) = Urchins_4650(t-dt) + (to_4650to_5l55-die_10) * dt
INIT Urchins_4650 = 250000 {urchin}
INFLOWS:
to_4650
OUTFLOWS:
(IN SECTOR: Urchins 4145)
to_5155 = (Urchins_4650-die_10l/tto_10 {urchin/month}
die_10 = (nat_death_rate*Urchins_4650) +
number4650eaten {urchin/month}
avgwt_10 = 0.04502 {kg/urchin}
kg4650eaten = if Biomass_30plus> = Kg_Urchin_consumed
then Kg_Urchin_consumed*rel_denslO else total_wtlO {kg}
number4650eaten = kg4650eaten /avgwt_10 {urchin}
rel_denslO = if Biomass_30plus and total_wtlO >0 then
(total_wtlO/Biomass_30plus) else 0 {unitless}
total_wt10 = avgwt_10*Urchins_4650 {kg}
tto_10 = 63 {month}
Urchins 5155
Dead_ll(t) = Dead_ll(t-dt) + (die_1l) * dt
INIT Dead_ll = 0 {urchin}
INFLOWS:
die_ll = (nat_death_rate*Urchins_5l55) +
number5l55eaten {urchin/month}