A Comparison of the Ubiquinone Contents Between Two Groups of Adult Chum Salmon, Oncorhynchus keta, Caught both in the Bay and the River

Ubiquinone is a natural benzoquinone, which is now recognized as an essential component in the electron transfer chain of mitochondria for many forms of life. In order to get some insight into the biochemical basis underlying the physiological adaptation of the chum salmon during its return to spawn in the river, tissue levels of ubiquinone in the salmon were examined. The dominant ubiquinone in chum salmon was identified as ubiquinone-10 by chromatographic comparison with standard ubiquinone-9 and ubiquinone-10. The concentrations of ubiquinone in the tissue of salmon captured by a trap at a designated sea spot (Otsuchi Bay) were 82.7, 36.2, 27.3 and 12.4 μg per gram of wet tissue in heart, liver, kidney and gills respectively, while the values obtained from the salmon captured in the river (Otsuchi river) were 81.2, 49.9, 28.7 and 18.0 μg respectively. Of the tissues examined, a significant increment in the ubiquinone concentration (ca. 45%) was observed only in the gills of the salmon captured in the river, suggesting the biochemical significance of gills in sea water-fresh water transition of the chum salmon.