GEOGRAPHIC DISTRIBUTION OF THE PACIFIC SALMON 
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surface temperatures tolerated by the salmon during their spawning and seaward 
migrations approximate 0° C. at the minimum and are in the vicinity of 20° C. at the 
maximum. 
Information thus far available indicates that the Pacific salmon, during their 
sojourn in the sea, frequent the subsurface waters to depths of 200 meters. Hence, 
the mean annual temperatures at 200 meters were studied in relation to the distribu- 
tion of the salmon. These mean temperatures for the North Pacific are shown by the 
Figure 2.— The geographic distribution of the Pacific salmon and the mean surface ocean temperatures during the spawning migra- 
tion period of the salmon. The bars indicate the native distribution of the salmon, the solid black areas indicate the regions in 
which the salmon have been transplanted successfully, and the dots indicate the regions in which the transplantations were 
unsuccessful. The isotherms in the North Pacific Ocean give the mean surface temperatures for the period of June, July, August, 
and September. Those in the North Atlantic Ocean give the mean surface temperatures for the period of July, August, and 
September, and those in the South Atlantic and South Pacific Oceans give the mean surface temperatures for the period of 
January, February, and March. 
isotherms in figure 3. Schott (1935) gives a review of the oceanographic studies 
carried on in the North Pacific and describes the subsurface temperatures in this 
region. The isotherms in figure 3 were taken primarily from Schott’s review. 
Along the coasts of Japan and Korea the mean annual 10° and 5° C. isotherms, 
respectively, at 200 meters, describe the subsurface temperatures of the waters at the 
southern distributional boundaries of the salmon. The mean annual temperatures at 
200 meters on the east coast of Honshu Island, Japan, decrease from 10° to 3° C. within 
the comparatively short distance from Cape Inuboye to the north end of the island. 
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