Inflexibility of vertebral number in chum salmon Oncorhynchus keta

Abstract

Chum salmon Oncorhynchus keta eggs from the Chitose and Shiriuchi rivers in Hokkaido, northern Japan, were incubated under identical conditions with the aim of comparing vertebral number (V N ) to that reported archived data from the 1950s. The comparison revealed that mean V N of salmon from the Shiriuchi River has remained unchanged for 50 years and is higher than that from the Chitose River. The V N in the Chitose River salmon was found to be significantly higher than that recorded in the archival data. The variation in the mean V N of chum salmon fry collected during different seasons and years in the Chitose River falls within a range that has remained constant, suggesting that the difference between the values obtained in our study and the archival data may be due to differences in the timing of egg collection. These results indicate that the mean V N of chum salmon has been stable for a long period. Incubation experiments under identical conditions are a useful tool for examining changes in genetic structure and detecting the essential properties of populations.

Seasonal variations in and effect of incubation water temperature on vertebral number in naturally spawning chum salmon Oncorhynchus keta

“…Differences in meristic characters among seasonal races may have genetic and environmental components, and even an interaction between these components. V N is a heritable trait in Pacific salmon [5][6][7][8], and this character is also conserved under similar conditions in chum salmon [28]. In this study, the V N of chum salmon juveniles changed according to incubation water temperature, and the reaction norm was a V-shaped curve that was lowest at 9°C.…”

“…Tallman and Healey [4] reported that, within a river, a late spawning population had fewer vertebrae than a temporally separated early spawning population. It is suggested that the mean V N of the latespawning population was lower than that of the early spawning population in the Chitose River, Hokkaido Island [28]. Differences in meristic characters among seasonal races may have genetic and environmental components, and even an interaction between these components.…”

Effects of spawning time on the variation of vertebral number in chum salmon Oncorhynchus keta

“…These results suggest that variations of vertebral number in chum salmon adults and fry are aŠected by spawning time, and that the variations are originally caused by genetic factors. Ando et al13) は，千歳川のサケの脊椎骨数を…”