Research articleNatural and artificial spawning strategies with fresh and cryopreserved semen in Rhamdia quelen: Reproductive parameters and genetic variability of offspring

This study evaluated the reproductive parameters and genetic variability of offspring of Rhamdia quelen from mating by natural spawning and by controlled fertilization with fresh and cryopreserved semen. After hormonal manipulation, three R quelen pairs were used for natural spawning in high-flow tanks, three pairs were used for mating with fresh semen, and another three pairs were used with cryopreserved semen. Matings were performed in triplicate. For matings with fresh and cryopreserved semen, semen from each male was used to individually fertilize oocytes from each female. Pools of semen and oocytes were made, and aliquots of these gametes were taken for fertilization. No differences (P > 0.05) were detected for absolute or relative fecundity, fertilization rate, or egg hatching rate. The use of fresh semen led to a higher (P < 0.01) percentage of normal larvae. The use of fresh semen in pooled mating resulted in a greater effective number of alleles and a higher expected heterozygosity. Offspring from natural spawning presented higher observed heterozygosity and a lower inbreeding coefficient. The highest inbreeding coefficient was found in offspring from individual matings using fresh semen. Regarding paternal contributions, a single male dominated in matings with fresh semen, whereas two males dominated in natural spawning and matings using cryopreserved semen. The use of gamete pools for mating and natural spawning resulted in higher genetic variability of offspring, and mating using cryopreserved semen found no effects on genetic variability of offspring but did reduce the percentage of normal larvae. Other reproductive parameters were not influenced by spawning strategies.