228
11. Horseshoe Crabs and Shorebirds
HORSESHOE CRAB AND SHOREBIRD DYNAMICS
ADULT HORSESHOE CRAB MODULE
ADULT_CRABS [GENDER] (t) = ADULT_CRABS [GENDER] (t-dt) +
(PROMOTION[GENDER]-NATURAL_DEATH[GENDER]STRANDING[GENDER]-EXPLOITATION[GENDER]) * dt
INIT ADULT_CRABS [GENDER] = 1851823
INFLOWS:
PROMOTION [MALE] = 0.5*JUVENILES_TO_ADULTS {CRABS PER
SEASON}
PROMOTION [FEMALE] = 0 .5*JUVENILES_TO_ADULTS {CRABS PER
SEASON}
OUTFLOWS:
NATURAL_DEATH [MALE] = ADULT_CRABS[MALE] /ADULT_YEARS
{CRABS PER SEASON}
NATURAL_DEATH [FEMALE] = ADULT_CRABS[FEMALE] /ADULT_YEARS
{CRABS PER SEASON}
STRANDING [MALE] = ADULT_CRABS [MALE] *STRANDING_RATE
{CRABS PER SEASON}
STRANDING [FEMALE] = ADULT_CRABS [FEMALE] *STRANDING_RATE
{CRABS PER SEASON}
EXPLOITATION [MALE] =
ADULT_CRABS[MALE]*CONCH_RATE+(O*EEL_RATE) {CRABS PER
SEASON}
EXPLOITATION [FEMALE] =
ADULT_CRABS [FEMALE] *EEL_RATE+ADULT_CRABS[FEMALE] *CONCH_
RATE {CRABS PER SEASON}
ADULT_YEARS = 8 {SEASONS}
CONCH_RATE = 0 {0.3 CRABS PER CRABS PER SEASON}
EEL_RATE = 0 {.15 CRABS PER CRABS PER SEASON}
STRANDING_RATE = .1 {CRABS PER CRABS PER SEASON}
BIRD MODULE
BIRDS(t) = BIRDS(t-dt) + (BIRD_MATINGBIRD_NATURAL_DEATH) * dt
INIT BIRDS = 1312000 {BIRDS}
INFLOWS :
BIRD_MATING = BIRDS*FITNESS*0.5 {BIRDS PER SEASON}
OUTFLOWS:
BIRD_NATURAL_DEATH = BIRD_DEATH_RATE*BIRDS {BIRDS PER
SEASON}