678 
BULLETIN OF THE BUREAU OF FISHERIES 
Uda and Okamoto (1930), and Uda (1931), give the monthly temperatures at 100 
meters along these shores. The temperatures at 100 meters along the Korean coast 
do not differ appreciably from those at 200 meters and vary no more than 3° C. 
throughout the year. The temperatures at 100 meters along the east shore of Honshu 
Island average from 3° to 4° C. higher than at 200 meters and also vary no more than 
3° throughout the season. In general the subsurface temperatures in this region do 
not fluctuate widely throughout the year. 
Figure 3.— The geographic distribution of the Pacific salmon and the mean annual subsurface ocean temperature at 200 meters depth. 
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 
give the mean annual subsurface temperatures at 200 meters depth. 
The southern distribution of the salmon along the North American continent falls 
well within the region bounded by the mean 8° C. subsurface isotherm. Here again 
the subsurface waters vary only 2° to 3° C. throughout the year. In the Bering Sea 
the mean annual temperature at 200 meters is less than 3°, and in the Arctic Ocean 
it is less than 0° C. Hence, if the salmon frequent the subsurface waters to depths of 
200 meters, they must be tolerant to temperatures ranging from slightly below 0° at 
the minimum to the vicinity of 10° C. at the maximum. 
Donaldson (1936) has shown that the optimum range of temperature for growth 
of the young salmon in fresh water is between 13° and 17° C. Furthermore, he found 
that mortality was excessive at constant temperatures of 20° and 3° C. In view of the 
