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12. Kelp, Urchins, and Otters in the California Coastal Region
tto_1 2 = 24 {month}
Urchins 60plus
Dead_13 (t ) = Dead_l 3 (t - d t) + (Di e_13) * d t
I NIT Dead_1 3 = 0 {u r ch i n }
I NFLOWS:
Die_13 = number60pluseaten+(Urchins_60plus *1) {urchin}
Urchins_60plus(t) = Ur ch i ns _ 60p l us (t - d t ) + (to_60plusDie_l3) * dt
INIT Urchins_60plus = 1 00000 {u r chi n }
INFLOWS:
to_60plus
OUTFLOWS:
(IN SECTOR: Urchins 5660)
Die_1 3 = number60pluseaten+(Urchins_60plus*1) {urchin}
avgwt_13 = 0 .098 {kg /urchin}
kg60p luseaten = if Biomass_30plus > =
Kg_ Ur ch i n_ co ns umed then Kg_ Ur ch i n_ co ns umed* r e l _d ens1 3
else total_wt 13 {kg}
number60pluseaten = kg 60p l u s e a t en / avgwt _ 13 {urchin}
rel_dens 13 = if t otal_wt 13 and Biomass_30plus > 0 then
(t o t a l _wt13 / Bi oma s s _3 0p l us ) else 0 {uni t l e s s}
to t a l_wt 13 = avgwt_13 *Urchins_60p lus {kg}
Urchins 61 0
dead2(t) = dead2( t -dt ) + (d i e2 ) * d t
I NIT dead2 = 0 {urchin}
INFLOWS :
die2 = (Ur ch i n_ 61 0*na t _d e a t h_ r a t e ) + numbe r610eaten
{urchin/month}
Urchin_610(t) = Urchin_610 (t-dt) + (to_610-t o_111 5die2) * dt
INIT Urchin_610 = 200000 {urchinsl019 per 4 sq.km}
INFLOWS:
to_610 (IN SECTOR: Urchins05)
OUTFLOWS:
t o_1115 = (Urchin_6 10-die2) /tto_2 {urchin /month}
di e 2 = (Ur ch i n_6 10* na t _de a t h_ r a t e ) + number610eaten
{urch i n/mon t h}
Ave_Wt2 = 0. 000 27 {kg /urchin }