Influence
of photoperiod on the onset of gonadogenesis in Eurasian perch Perca
fluviatilis
H.
Migaud, P. Fontaine, P. Kestemont, N. Wang, J. Brun-Bellut-2004
Aquaculture, 241(1-4): 561-574
Abstract:
The
aim of the study was to improve our knowledge on the environmental control
of Eurasian perch, Perca fluviatilis, reproductive cycle and
determine the effects of photoperiod regimes on the onset of gonadogenesis.
Under ambient thermal conditions, three photoperiodic regimes were tested in
triplicate: a continuous photophase (24L/0D), a constant photoperiod
(16L/8D) and a natural photoperiod. The gonadosomatic index (IG)
was calculated and plasma estradiol (E2) and testosterone (T)
levels were measured. This study showed that a 24-h photophase, applied to
fish from mid-July to the beginning of October, inhibits the initiation of
gametogenesis (IG below 2% and 1% in females and males,
respectively). A constant photoperiod (16L/8D) resulted in a very
heterogeneous gonadal development. Twenty percent of females and 40% of
males developed their gonads and mean IG reached lower
values than in females and males from the natural photoperiod. In the
natural photoperiod treatment, gonadal development in all fish was
comparable to that of fish observed in natural habitat at the same period of
the year (IG above 3%). Seasonal variations in daylength
seem to be involved in the initiation of gametogenesis in perch, whereas
continuous photophase inhibits gonadal development. Photoperiodic variations
play a crucial role in the initiation of perch reproduction.
(aLaboratoire
de Sciences Animales, INRA-INPL-UHP, Nancy 1, MAN, 34 rue Sainte Catherine,
54000 Nancy, France, e-mail of H. Migaud: herve.migaud@stir.ac.uk,
e-mail of P. Fontaine: pascal.fontaine@lsa-man.uhp-nancy.fr,
e-mail of P. Kestemont: patrick.kestemont@fundp.ac.be,
e-mail of J. Brun-Bellut: Jean.brun-bellut@iutnb.uhp-nancy)