Effect of temperature and photoperiod on sexual maturation and spawning of the common carp: I. Under conditions of high temperature

Abstract

Common carp or “Magoi”, Cyprinus carpio (Linnaeus), were reared under constant 24°C and different photoperiod conditions following induced spawning in July. Under a 12L–12D photoperiod, half of the females spawned partially within 6 months, and by the tenth month two of 14 females had spawned totally twice and eight on one occasion. Under a 16L–8D photoperiod, 12 of 15 females spawned totally after 3 months, and six of them spawned again in another 3 months. During the first 10–11 months, the fish were in an “active spawning phase”. Females retained on these regimes for another year did not spawn again although they held matured oocytes. They were in a “passive spawning phase”, because temporary cooling of the tank water to 16°C was effective in inducing immediate spawning. In the “active spawning phase”, gonadal maturation was accelerated when fish were transferred from 12L–12D to 16L–8D, but not when they were transferred from 16L–8D to 22L–2D. In the “passive spawning phase”, lengthening of the photoperiod was not effective.