• abdominal vertebrae;
  • caudal vertebrae;
  • genetic correlation;
  • heritability;
  • masu salmon

ABSTRACT:  Ten sibship masu salmon Oncorhynchus masou masou families were produced to estimate the heritability of the number of abdominal vertebrae (AV) and caudal vertebrae (CV), and the genetic correlation between the two traits were calculated. The AV and CV of both the parents and their offspring were counted separately, and the heritability was estimated by performing parent–offspring regression analysis. The mean vertebral number of the offspring differed among families although they were reared under identical water temperature conditions and had the same parental vertebral number type in crossbreeding. The heritabilities were estimated as 0.65 for AV and 0.84 for CV. The genetic correlation between the number of AV and CV was calculated as −0.92. These results suggest that AV and CV are governed by genetic components even when the fish are reared under identical environmental conditions, and the total vertebral number is expected to converge within a certain range. It is necessary to analyze separately the variations in the number of AV and CV when investigating the vertebral number in masu salmon.