248
12. Kelp, Urchins, and Otters in the California Coastal Region
INFLOWS:
to_3640
OUTFLOWS:
(IN SECTOR: Urchins 3135)
to_4145 = (Urchin_3640-die_8) /tto_8 {urchin/month}
die_8 = (nat_death_rate*Urchin_3640) + number3640eaten
{urchin/month}
avgwt_8 = 0.02308 {kg /urchin}
kg3640eaten = if Biomass_30plus > = Kg_Urchin_consumed
then re l_dens_8*Kg_Urchin_consumed else total_wt8 {kg}
number3640eaten = kg3640eaten /avgwt_8 {urchin}
rel_dens_8 = if total_wt8 and Biomass_30plus > 0 then
(total_wt8 /Biomass_30plus) else 0 {unitless}
total_wt8 = Urchin_3640*avgwt_8 {kg}
tto_8 = 25 {month}
Urchins 1115
Dead3{t) = Dead3{t-dt) + (die3) * dt
INIT Dead3 = 0 {urchins}
INFLOWS:
die3 = (Urchin_1115*nat_death_rate) + numberll15eaten
{urchin/month}
Urchin_1115{t) = Urchin_1115 (t-dt) + (to_1115-die3to_1620) * dt
INIT Urchin_1115 = 600000 {ur ch i n s 2029 per 4 sq. kID.}
INFLOWS:
to_1115
(IN SECTOR: Urchins 610)
OUTFLOWS:
die3 = {Urchin_1115*nat_death_ratel + numberll15eaten
{urchin/month}
to_1620 = {Urchin_1115-die3) /tto3 {urchin/month}
ave_wt_3 = 0.00107 {kg /urchin}
Biomass_1029 = total_Wt2 + total_wt3
kgl115eaten = if Biomass_30plus < Kg_Urchin_consumed
and Biomass_1029 > = Kg_Urchin_consumed then
Kg_Urchin_consumed*rel_dens3 {kg urchin}
else if Biomass_30plus < Kg_urchin_consumed and
Biomass_1029 < Kg_Urchin_consumed then total_wt3 else 0
{kilograms of urchins2029 eaten per month}
numberll15eaten = kgll15eaten /ave_wt_3 {urchins}