experiments of It^SO, It was found from these graphs that during the winter 

 season the most fish are taken when the temperatures at both the surface 

 and at 100m are 18^-1 a^Cj. the greatest number of catches is made at 

 IS^'-SO^Cp and the largest average catch per tiine fished is obtained at 

 17°<=.19**Co A point to be noted herej, however ^ is that in the Zunan area 

 the yearly average temperature at the lOQm level is about 20°C and the 

 yearly average variation is about 9**^^ these values being smaller than 

 the yearly average of 22°C and the yearly variation of 13°C in the sur<= 

 face temperatures o These temperatures are higher than those found in the 

 waters north of Kinkasan (yearly average below lO'^j, yearly variation 10° ■= 

 12° C) and the yearly variation is les6^)o Accordinglyp the belief that 

 the level of favorable temperatures is limited to a narrow range is not an 

 error resulting from concentration on the 100m level as can be seen from 

 the fact that there are rather large seasonal variations in the water 

 temperatures at lOQoo 



An experiment in correcting the surface water temperature to the tempera^ 

 ture favorable^or eatctiing i'iish" The data ar'e~drawn from charts sub- 

 mitted to the Fisheries Experiment Station by the PSlcai Enyo COo showing 

 the fishinc grounds, number of fish takenj, and surface temperatures for 

 the albacore catches for each montho Seeking to find the distribution of 

 the eaten in relation to the surface temperature a mode was obtained at 

 about 2 0*^^ however J, it is thought that there will be a marked variation 

 durir.5 the season when the temperatures oesome stratifiedj as described 

 above, i*^) These data cover only surface temperatureSp and observations 

 for the middle and lower levels are lacking ^ According to Table 1 the 

 depth at which fish are taken in the Zunan area may be thought to be 

 50-lOQm or 100m« In converting the surface temperature to the temperature 

 at the fishing level the most reasonable method is probably to correct it 

 by using the results of vertical observations on the fishing ground in 

 question for the month under consideration^ but this is difficult 

 under present conditions » While it is a method greatly lacking in 

 precision, what has been done has been to adopt the average temperatures 



'' for each month at a point 100 miles southeast of Nojimasaki in Chiba 

 Prefecture as representative of the vicinity of the center of this fishing 

 ground Prom these values I aave subtracted 0o5°C in January^ 0®C in 

 February, Oo5^C ir. '::arch, l^'C in April, 2°C in May^ 3°C in June, 5°C in 

 JulVp and 1*^1; in December, and have taken this as the temperature at the 

 lOOm levelo ■' The correlation between this temperature at iOOm and the 



9^ 

 ' Uda^ Michitaka« Monthly Oceanograpnic ., -l" u:.-:ion of tne f.uroshic and 



Oyaahio Currents in Averap;e Yearso Fisheries Experiment Station Report 



No„ 3. 1933 „ pp. 100=102 o 



^^' Uda, Michitakag An Observation on the Albacore Fishing Situation and 



-.he Oceanographic Conditions in the Zunan Area, Report of the Symposium 



on Fisheries physics, NOo 27 „ July I951<, 



11 ) 



' In doing this the differences from year to year and from place to place 



In the curve of vertical distribution of water temperatures from 0=100m 



within a particular sea area for a given month were ignored and the 



declination in the temperatures at the surface and at the 100m level 



were assumed to be alwv,'8 enualo 



