Influence of photoperiod on reproductive performances in Eurasian perch Perca fluviatilis

The aim of the study was to determine the effects of photoperiod regimes under natural temperature conditions on reproductive performances (gametogenesis, spawning quality) in Eurasian perch Perca fluviatilis. During a 10-month experiment, fish were reared in 12 tanks (3000 L, 88 fish/tank, initial mean weight of 300 g, age of 2+) in an outdoor water-recirculating system and subjected to 4 photoperiod regimes in triplicate: continuous lighting (24L:0D), constant photoperiod (16L:8D), simulated natural (SNP) and natural (NP) photoperiods. Gametogenesis, spawning time and egg quality were studied. No gonadal development was observed in males and females under 24L:0D treatment. The 16L:8D treatment resulted in heterogeneous gametogenesis with only 54% of gravid females and less than 30% of maturing males. A normal gametogenesis was observed under NP and SNP conditions with 100% of gravid females and spermiating males during the spawning period. Under SNP and 16L:8D regimes, spawning period was delayed in comparison to NP regime and 45% and 65% of the maturing females did not spawn, respectively. All spawning were released and harvested between dawn and 4 p.m., independently of the photoperiodic regime applied. These results show that daily lighting variations are important in the control of Eurasian perch spawning. Significantly higher fecundities were observed under SNP and NP regimes compared to 16L:8D. The photoperiod regimes and artificial lighting significantly affected egg quality, as fertilization rates in 16L:8D and SNP groups were very low (7.7% and 3.3% respectively) compared to the NP treatment (57.2%). Hatching rates were null in SNP and 16L:8D regimes, whereas a 54% hatching rate was estimated in NP treatment. Finally, high mortality rates were recorded during the spawning period. These mortality rates were significantly higher in 16L:8D and SNP treatments (63-72%) than in NP and 24L:0D treatments (36-40%).(...)