Controlled reproduction of the crucian carp Carassius carassius (L.) combining temperature and hormonal treatment in spawners

Summary Five separate experiments were carried out on selected aspects of wild crucian carp controlled reproduction including: (a) spawner handling time after catching, (b) water temperature, (c) type of hormonal stimulation and (d) hormonal treatment procedures. The highest ovulation rates and embryo survival rates were obtained when fish were subjected to hormonal preparations within one to 3 days after capture. Administering the ovulation‐inducing injections at 17, 21 and 25°C, a temperature regime around 21°C can be regarded as the optimum for controlled reproduction of the crucian carp (80% of ovulated females; 87.5% embryonic survival rate; 159 eggs per g of female body weight). Much better results were achieved when injections were applied in two‐stages: 12‐h interval application of the dosing scheme as compared to 6 and 24 h intervals. The highest ovulation rate (~90%) was obtained in the groups stimulated with commercial preparations containing a LHRH analogue and dopamine inhibitor: Ovopel (dose 1.2–2.0 pellet kg−1 BW) and Ovaprim (dose 0.5–0.6 ml kg−1 BW). From the control group (treated with a 0.9% solution of NaCl), no females ovulated. These results are considered significant for aquaculturists engaged in controlled reproduction of crucian carp and other cyprinids.