12.5. Questions and Tasks
253
Urchins_5155(t) = Urchins_5155 (t-dt) + (to_5155to_5660-die_ll) * dt
INIT Urchins_5155 = 550000 {urchin}
INFLOWS :
to_5155
OUTFLOWS:
(IN SECTOR : Urchins 4650)
to_5660 = (Urchins_5155-die_ll) /tto_ll {urchin/month}
die_II = (nat_death_rate*Urchins_5155) +
number5155eaten {urchin /month}
avgwt_ll = 0.05978 {kg /urchin}
kg5155eaten = if Biomass_30plus > = Kg_Urchin_consumed
then Kg_Urchin_consumed*rel_densll else total_wtll {kg}
number5155eaten = kg5155eaten /avgwt_ll {urchin}
rel_densll = if total_wtll and Biomass_30plus > 0 then
(total_wtll /Biomass_30plus) else O{unitless}
total_wtll = Urchins_5155*avgwt_11 {kg}
tto_11 = 31 {urchin}
Urchins 5660
Dead_12(t) = Dead_12 (t-dt) + (die_12) * dt
INIT Dead_12 = 0 {urchin}
INFLOWS :
die_12 = (nat_death_rate*Urchins_5660) +
number5660eaten {urchin/month}
Urchins_5660(t) = Urchins_5660(t -dt) + (to_5660to_60p1us-die_12) * dt
INIT Urchins_5660 = 250000 {urchin}
INFLOWS :
to_5660
OUTFLOWS :
to_60plus
(IN SECTOR: Urchins 5155)
(Urchins_5660-die_12) /tto_12 {urchin/month}
die_12 = (nat_death_rate*Urchins_5660) +
number5660eaten {urchin/month}
avgwt_12 = 0 .07736 {kg /urchin}
kg5660eaten = if Biomass_30plus > = Kg_Urchin_consumed
then rel_dens12*Kg_Urchin_consumed else total_wt12 {kg}
number5660eaten = kg5660eaten /avgwt_12 {urchins}
rel_dens12 = if total_wt12 and Biomass_30plus > 0 then
(total_wt12 /Biomass_30plus) else 0 {unitless}
total_wt12 = Urchins_5660*avgwt_12 {kg}