Induction of out-of-season
spawning in Eurasian perch Perca fluviatilis: effects of rates of
cooling and cooling durations on female gametogenesis and spawning
H.
Migaud, P. Fontaine, I. Sulistyo, P. Kestemont, J.-N. Gardeur-2002
Aquaculture, 205(3-4): 253-267
Abstract:
This study was designed to determine the influence of
different thermal conditions during an out-of-season reproductive cycle on
gonad recrudescence, plasma steroid levels (testosterone and estradiol),
vitellogenin (VTG) concentrations and spawning in Eurasian perch (Perca
fluviatilis) females. The experiment was performed in 450-l square
polyester indoor tanks located in two rooms equipped with controlled light
and temperature devices. Four thermal regimes were tested with two different
rates of cooling from 21 to 6 °C, 3 weeks (3w) or 6 weeks (6w), and two
different durations at 6 °C, 3 months (3m) or 5 months (5m). The
photoperiod was fixed at LD 12:12. A long cooling period (6w) resulted in
greater gonadosomatic index (GSI) (3.6±0.5%) correlated with a larger
oocyte diameter (787.9±25.1 µm). The plasma levels of testosterone (13.63±1.18
ng ml-1) in the former groups were higher than in the short
cooling period groups (6.82±0.9 ng ml-1). A longer duration at 6
°C (5m) resulted in higher GSI (14.8±1%), plasma testosterone levels (26.2±0.4
ng ml-1) and plasma protein phosphorus (PPP, 1.33±0.3 µg ml-1).
The fish from the 6w 5m batch showed the highest plasma estradiol and
testosterone levels, whereas the 3w 5m group showed the largest GSI. At the
end of the experiment, several spontaneous out-of-season spawnings were
collected in batch 6w 5m. Biopsy showed that most oocytes from groups 3w 5m
and 6w 5m females were mature (migration of the germinal vesicle from
central position), whereas few females showed a beginning of migration in
groups 3w 3m and 6w 3m, suggesting that the gonad development and
reproductive success of Eurasian perch mainly depends on the chilling
duration (long cold period) rather than on the cooling one, in order to
obtain out-of-season spawning.
(Laboratoire de Sciences Animales, INPL-UHP, Nancy 1,
MAN 34 rue Sainte Catherine, 54000 Nancy, France, Tel.: +33-383-302-841;
fax: +33-383-323-016, e-mail: herve.migaud@lsa-man.u-nancy.fr)