Duration of chilling phase, but not thermal condition, influence the gonad maturation of male and female domesticated pikeperch ( Sander lucioperca )

Abstract This study was designed to determine the influence of the thermal level and duration of chilling period on the initiation and progress of gonadogenesis and gametogenesis under controlled conditions in pikeperch ( Sander lucioperca ). A set of 120 fish was distributed into eight tanks (15 fish per tank). The effects of two temperatures (6 or 12°C) in combination with two durations of chilling period, either short (S; 75 days at 6°C and 125 days at 12°C) or long (L; 135 days at 6°C and 185 days at 12°C), were investigated for the effect on growth, gonadosomatic index (GSI), hepatosomatic index (HSI), gamete developmental stage and sex‐steroid levels (17 beta‐estradiol‐E2 and testosterone‐T). These zootechnical and physiological parameters were selected as they reflect the progressive advancement of gametogenesis in percids including pikeperch. The results show that the temperature did not affect the reproductive parameters but down‐regulated the HSI and the condition factor in females. In addition, the exposure to a longer chilling period, whatever the temperature, allowed for (1) further advancement of gonadogenesis in females (GSI = 6.5% vs. 11%), (2) further advancement of gametogenesis (0% vs. 60% of oocytes at late vitellogenesis, 15% vs. 80% of spermatozoa in males) and (3) the maintenance or increase of plasma sex steroids in both sexes (e.g. 10 ng/mL vs. 27 ng/mL of T in females). Together with already published data, these results suggest that, depending on the features of fish populations and photothermal programmes, the maintenance of temperature at either 6 or 12°C does not necessarily impact pikeperch gonad maturation. However, the duration of the chilling period is an important factor for the optimization of gonadogenesis and gametogenesis achievement before reproduction.