scant to provide any further information about these shifts, but sincS they do occur, it clearly is 

 necessary to plan the scouting to include a considerable area around the islands if our results are 

 to be comparable with those of the local fishing fleet. 



Table 1 1, --Abundance of skipjack schools by area 



— The scouting of the northeast sector during GILBERT cruise 7 was not on 

 the regular arms of Area I (see fig. 2) 



24° 



160° 



158° 



160° 



158° 



156° 



CRUISE II -APRIL 



CRUISE 13- JUNE 



When the cross-like patterns of scouting were laid out for the February, April, and June 

 cruises, it was thought that any concerted movement of schools through the area might be detect- 

 able by a "Doppler effect" and by means of vector analysis the direction of movennent might be 

 determined. The number of schools sighted on certain arms of the areas scouted do indeed sug- 

 gest a Doppler effect (fig. 7). For exannple, in Area I during April we found 8 schools while 



traveling west and only 3 on our 

 return towards the east. On the 

 south arm we found 12 schools 

 while heading south and 7 while 

 proceeding back toward the 

 center. Sinnilar results were 

 obtained in the south and west 

 arms of Area II in April, and 

 during June on the east and west 

 arnns of Area I, on the west arm 

 of Area II, and on the west arm 

 of Area IV. These all show that 

 more schools were sighted on 

 runs toward the south and west 

 than were seen on the reciprocal 

 runs toward the north and east. 

 If this could be ascribed to a 

 Doppler effect, then the schools 

 would have been moving toward 

 the northeast; a vessel meeting 

 the schools would encounter more 

 of them than a vessel proceeding 

 in the same direction as the 

 schools. 



til 



160° 



158° 



160° 



158° 



156° 



Figure 7. --Numbers of schools seen during systematic scout- 

 ing on the April and June cruises of the CHARLES 

 H. GILBERT. 



However, the weather is 

 definitely a factor here because 

 of the prevailing northeasterly 

 winds, which made the scouting 

 conditions poorer on the runs 

 toward the east and, to a lesser 



17 



