they were at about the same position in both year*, and from January on 



they seem to have moved south faster than in 1949. In 1949 and in 1951 



(November 1951 to March 1952) the main schools are seen to have reached 



o o 



29 N. around March of both years, but in 1950 they were already at 29 N, 



ir Jauiuary, In 1951 the southward movement is thought to have been slow 



in the first part of the fishing season, but from December on it moved at 



about the same speed as in 1949. It is difficult to make any judgments 



about the waters east of 150 E. because of the scarcity of data, but the 



trend of southward movennent of the schools there does not necessarily 



coincide with that in the area of 140 E. to 150 E. If it can be assumed 



that the catch rates are proportional to the quantity of schools present, 



throughout the sea areas as a whole it can be said that the quantity of 



fish was greatest in 1951. 



With regard to figure 1, it was stated that from November to 

 January north of the area of accumulation (or main group of schools) 

 where catch rates are high the catch rate curve trails out to a great 

 length, and if we consider this trailing portion to be a group of schools 

 which replenishes the main concentration, we can detect importeint dif- 

 ferences in the variations of the catch rates as between these two groups 

 of schools. The coefficient of variation in the catch rate is small for the 

 main group or accumulated group and shows large values for the replen- 

 ishment group. In other words, on the fishing grounds for the main group 

 or accumulated group, the fishing conditions are stable, but on the fishing 

 grounds for the replenishment group fishing conditions are unstable and 

 fluctuate widely. 



In the east-west direction, too, there appear to be variations from 

 year to year in the positions at which the fishing grounds develop. The 

 data used herein are almost entirely derived from connmercial fishing and 

 do not represent a deliberate disposition of vessels with the objective of 

 investigating changes in the locations of the fishing grounds, so what they 

 actually show is the pattern of operations of the commercial fleet. This 

 fact nnust be fully taken into consideration. But if we take it that the grounds 

 where the fishing vessels concentrate are the main grounds, then the follow- 

 ing conclusions can be drawn from table la, b, and c. In 1949 the fishing 

 grounds developed on about an average year's pattern, but in 1950 the grounds 

 east of 140 E. were, on the whole, pushed to the eastward, while in 1951, in 

 general, they were pushed to the westward. 



It has already been stated that between 150 E. and 160 E. the catch 

 rates at the beginning of the fishing season are lower than they are in the 

 areas to the east and west. In the following discussion we will divide the 

 fishing grounds of the North Pacific into those west of 150 E. , those between 

 150 E. and 160°E., and those east of 160°E. 



31 



