Comparative study of male brood stock populations of rainbow trout (Oncorhynchus mykiss) in Iran

Abstract:Rainbow trout, Oncorhynchus mykiss, is one of the cultured fishes in the cold and fresh waters of the world. In this project, the main objective is the evaluation of samples of all male brood stock populations of rainbow trout in Iran. Phenotype of male brood stocks was identified in three categories, namely unclear, clear and clear with orange bands. The results indicated that there were significant differences amongst the three different phenotypes, in terms of gonad weight, GSI, sperm volume and concentra-tion. Seemingly, phenotype 1 was inferior (P < 0.05). Sperm motility of phenotypes 3 and 2 were placed in the same group, while phenotype 1 and 2 were positioned in another cat-egory. Furthermore, there was a positive significant correlation between gonad weight and body weight, testis weight and GSI, total sperm volume and GSI, along with total sperm concentration and volume. This proved that there was a significant relation between the biological characteristics of rainbow trout sperms and its phenotype in Iran. It can be concluded that phenotypes 1, 3 and 2, respectively, were the most suitable phenotypes for mating and also promoting its percentage.