lehrádek temperature functions (Fig.4.15b) fitted to full-nutrition stage-duration data
(Campbell et al. 2001). At each hourly time step, 1/24th of the inverse of the stage
duration in days is added to the molt cycle fraction (MC). When MC reaches 1, it is
zeroed and stage is incremented by one. Finally, the physical submodel moves each
individual at each hourly time step by changing the location elements of its vector. All
females and developing young are consistently advected at the mean velocity for a 25
m mixed layer taken from the Quoddy model. Numbers of vectors in G 1 approach
200,000 per 100 G 0 females.
(^) When a winter- or spring-generation individual completes its C5 development, it
either matures or enters diapause by a random process. The fractional rates are 50 : 50
:: mature : diapause for winter and 10 : 90 for spring, values based on rough estimates
from a seasonal jaw development study (Crain & Miller 2001). Half of maturing
individuals are assigned as male (random process) and simply counted; half are
female and are stored with maturation date and location. Resting C5s are stored with
rest initiation dates and locations for mapping. The mature females of the G 1
generation are assigned to female vectors, and the model continues.
Population Dynamics
(^) Biological aspects of the model output (Fig. 4.16), without advection, show
substantial similarity to the GLOBEC Broad Scale Survey data on C. finmarchicus
development in the southern Gulf of Maine and over Georges Bank.
Fig. 4.16 Output of individual-based model of C. finmarchicus life-stage abundances
in the Gulf of Maine and Georges Bank area. Fifth copepodites moving to diapause
are not shown; equal numbers of the first generation matured and entered diapause.
Female abundances were quite low and represented by a line at 50 times their
numbers.