Constant darkness negatively affects the outcome of hormonally induced reproduction in cultured Eurasian perch females

This study aimed to assess the effect of constant darkness applied fish during controlled breeding on reproductive traits in domesticated females Eurasian perch. Based assumption that keeping reproduction operation may reduce stress, suspected be responsible for variable spawning effectiveness this species. Two conditions were assessed (16 h light per day [group 16L] and 0L], two tank replicates condition). The protocol involved a 7-day-long adaptation period group 0L where photoperiod was reduced by 2.3 down darkness. After period, hormone injections (salmon gonadoliberin analogue) both groups: priming (10 µg/kg) resolving (25 with 7-day interval between them. During study, morphometric indices recorded blood, brain, pituitary samples collected stress markers determine hypothalamic-pituitary-gonadal axis functioning via measuring blood plasma hormones, as well gonadotropins (luteinising [LH] follicle-stimulating [FSH]) transcript abundance (n = 7 each at sampling point). In addition, kinetics final oocyte maturation (FOM) process, ovulation rate, egg quality monitored 12 group). results indicated there no differences terms morphometry, FOM kinetics, most groups throughout experiment, except haematocrit, which increased immediately following acclimation kept Constant negatively affected levels 17α,20β-dihydroxy-4-pregnen-3-one (DHP) LH expression time second injection. exposure hormonal dose applied, resulted disruption ovulation, rates (50%) 0L, compared 16L (91%). findings clearly indicate have significant deleterious effects out-of-season induced, hormonally supported, reproduction. Therefore, we advise against use when managing broodstock