Influence des variations de la température et de la photopériode sur le cycle de reproduction et la qualité des pontes de la perche commune "perca fluviatilis"

Abstract : The aim of these experimental studies was to improve our knowledge on the environmental control of Eurasian perch reproduction. Under a constant photoperiod (12L : 12D), thermal variations (6 weeks of cooling from 22 to 6?C, 5 months of chilling at 6?C and 1 month of warming from 6 à 14?C) have shown some limits on the control of the reproductive cycle. Even if aIl the males were spermiating after a such regime, only few females have developed their gonads (31 %) and only 6 % have spawned. Moreover, the spawning quality was low. Thus, the influence of photoperiodic variations in the control of female gametogenesis was suggested and studied. A 24 hours photophase inhibits the initiation of perch male and female reproductive cycle. Some low sex steroids levels were measured. A constant photoperiod (16L: 8D) results in a very heterogeneous gonad development, lots of atresia, and few spawnings (30 %). Under a natural photoperiod, results, in terms of plasma sex steroids variations, gonad development and eggs and larvae quality, were similar to those observed in natural habitat. In simulated photoperiod conditions, although all the broodstocks have developed their gonads, only 55 % of the mature females have spawned and low fertilization rates were observed. Spawning seems to be triggered off by seasonal temperature and daily light intensity variations. Most of the spawnings occurred at dawn. In artificial light conditions, the sudden switch from darkness to daylight could disturb the oviposition process. The light-darkness cycle would be an important factor, but not sufficient to induce a normal gonadal development. Daylength variations are also involved in the initiation and the gonadal development during gametogenesis. Photoperiodic and temperature variations both play a crucial roIe in the success of perch reproduction. Finally, in April, while the water temperature rises, a high mortality increase was observed. It seems to be not linked to the reproductive cycle.
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Hervé Migaud. Influence des variations de la température et de la photopériode sur le cycle de reproduction et la qualité des pontes de la perche commune "perca fluviatilis". Sciences agricoles. Université Henri Poincaré - Nancy 1, 2002. Français. ⟨NNT : 2002NAN10030⟩. ⟨tel-01747409⟩

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