F. Carlotti et Hj. Hirche, GROWTH AND EGG-PRODUCTION OF FEMALE CALANUS-FINMARCHICUS - AN INDIVIDUAL-BASED PHYSIOLOGICAL MODEL AND EXPERIMENTAL VALIDATION, Marine ecology. Progress series, 149(1-3), 1997, pp. 91-104
A detailed individual-based model of egg production of Calanus finmarc
hicus is proposed. Female growth and egg production are represented by
8 state variables (gut content, nutrient pool, structural body, oil s
ac, and 4 stages of oocyte maturation) which are regulated by physiolo
gical processes. Clutch size is set constant under continuous food con
ditions, but the spawning interval changes with food availability and
temperature depending on the rate of oocyte maturation. Smaller clutch
es can occur when eggs are released under bad external conditions. Thu
s changing conditions can produce different clutch size distributions.
For model validation, egg production experiments were conducted under
different constant and fluctuating food concentrations and compared w
ith model simulations. In the experiments, egg production was strongly
affected by food fluctuation. In experiments with alternating feeding
and starvation cycles integrated egg production was affected by mean
food concentration during the experiment rather than by the frequency
of the cycles. The model reproduces correctly the egg production rates
and final body carbon of females kept in the different food regimes.
It provides a dynamical explanation of physiological responses of the
individual under short term food variation. When food becomes unavaila
ble, the most advanced oocytes are released and egg production continu
es until the nutrient pool decreases below a minimal critical value. T
hereafter, no eggs are laid. When food reappears, somatic growth resum
es until structural body weight is restored, then oogenesis is fuelled
. Experimental results were simulated correctly without using matter f
rom the lipid pool.