Figure 1.
Migratory route and scale from Japanese habitats and the distribution of anadromous salmonids in the Pacific region used in the present study.
Chum salmon (blue) have the largest natural range of any Pacific salmon, and undergo the longest migrations within the genus Oncorhynchus. Chum are found around the north Pacific, in the waters of Korea, Japan, and the Okhotsk and Bering seas, British Columbia in Canada, and from Alaska to California in the United States. The native range of pink salmon (green) is from the Arctic and Pacific drainages from Mackenzie River delta, the Northwest Territories, to the Sacramento River drainage, California (occasionally as far south as La Jolla, southern California) and in the west from the Lena River in Siberia to Korea. Populations in Asia occur as far south as Honshu in Japan. Masu (cherry) salmon (red) found in the Western Pacific Ocean along East Asia, range from the Kamchatka, Kuril Islands, Sakhalin and Primorsky Krai south through Korea, Taiwan and Japan.
Table 1.
Information of life history in the salmonids examined between May 2011 and February 2014 in the present study.
Figure 2.
Fluctuations of the radiocesium levels in the total Cs (top) between May 2011 and February 2014, 134Cs (middle) and 137Cs (bottom) between April 2012 and February 2014 after the F1NPP accident.
No significant temporal trends were found for all types of salmon suggesting the continued widespread distribution of these radionuclides with less convergence and indicating that these radionuclides remain in the natural environment for both terrestrial and marine ecosystems. All radiocesium data in the salmonids was from the information published by the Fisheries Agency of the Japanese Government [16] between May 2011 and February 2014. nd: not detectable due to levels below the detection limits.
Figure 3.
Differences in the radiocesium accumulations among the salmon species between May 2011 and February 2014 after the F1NPP accident.
Fluvial salmons exhibited significantly higher concentrations in each radiocesium than those of the anadromous salmon. The detectable rates were also higher in fluvial salmon than in anadromous salmon as presented in Table 2.
Table 2.
Radiocesium data information and radiocesium concentrations (above the detection limit) in the salmonids examined between May 2011 and February 2014 in the present study.