The influence of female body weight class on the effectiveness of controlled reproduction of carp Cyprinus carpio Linnaeus, 1758

The effects of Ovopel treatment and hypophysation on five different size classes (age = 4–16 years) of female carp, Cyprinus carpio L., from 10 breeding lines were assessed (class I: >3≤5 kg; class II: >5≤7 kg; class III: >7≤9 kg; class IV: >9≤11 kg; class V: >11 kg). Ovulation stimulation was done with carp pituitary homogenate i.e. CPH (0.3+2.7 mg kg⁻¹BW) or [(D‐Ala⁶, Pro⁹‐NEt)‐mGnRH+metoclopramide] i.e. Ovopel (1/5+1 pellet kg⁻¹BW). Analysis of variance included the results obtained in controlled spawnings carried out during 15 breeding seasons. The classification according to the body weight classes significantly (P ≤ 0.01) differentiated the weight of eggs (g) obtained both from CPH and Ovopel treated fish, the percentage of viable embryos (36 h) after CPH (P ≤ 0.05), number of eggs after CPH and Ovopel treatment (P ≤ 0.01) and number of living embryos (36 h) calculated per kg⁻¹CPH treated fish. The lowest weight of eggs was obtained after both the CPH and Ovopel application in class I and the highest in class V. The highest mean for the total number of eggs from CPH treated fish was noted for size classes IV and V and the lowest for class I. From Ovopel treated females the highest mean was noted in classes V and IV and the lowest in class I. The highest mean for the number of live embryos (36 h) calculated per kilogram CPH and Ovopel treated fish was recorded in female weight classes I and II. The lowest mean for this trait was found for size class V after both CPH and Ovopel treatment. The group of hypophysed females provided the best results of reproduction when the body weight was over 7 kg but not exceeding 9 kg (class III). Females treated with Ovopel reached such results when body weight was higher than 9 kg but did not exceed 11 kg (class IV). After both CPH and Ovopel treatment the poorest results were noted in females exceeding 11 kg body weight (class V). The predicted regressions for the number of viable embryos (36 h incubation) obtained per 1 kg female BW allows to determine in which weight class which stimulator offered the best predictability for this trait.