ability of skipjack during the season. The other index has no 

 predictive value because it occurs with the onset of fishing. 



terns, the first present throughout the year. During the year, 

 the trade-wind system changes in intensity, size, and location. 



Although our predictions of relative catch level have proved 

 useful so far, we cannot predict favorable fishing conditions 

 and catch levels with assurance until we better understand 

 the relation between skipjack and the environment. Two major 

 oceanographic problems will be investigated by this program: 



(1) environmental conditions that attract the fish to the Ha- 

 waiian Islands and make them available to the fishermen, and 



(2) the nature of the physical processes causing changes in 

 the environment. To understand these physical processes we 

 need to understand the relation between the wind system and 

 surface water motion in the Hawaiian region and to know the 

 factors that determine changes in subsurface circulation. 



600 

 ?2 5(X) 



§£ 



^,'100 

 |Z300 

 SF200 



1959 



15)54_ 



'»^^ 



1961 i 



1962 



J3.63.?. 



1955i 



"1950" 



1951-1960 MEAN 



1952; 



♦1958 

 1957 



TWO INDICES fwoiubij: 



ONE INDEX EWORABLE 

 ONE INDEX IINEWORABLE 



TWD INDICES UNFAVORABLE 



Figure 8. — Annual skipjack landings per boat In 



Hawaii related Co environmental Indices, 



Over the North Pacific, there are three major types of 

 wind systems: one Is the trade-wind system associated with 

 the pressure gradient between the North Pacific high and the 

 Equatorial pressure trough, the second lies between the North 

 Pacific high and the Aleutian low, the third between the Aleu- 

 tian low and the Asiatic high. The last two are winter sys- 



Figure 9 shows the locations about which the trade-wind 

 system is centered. In the spring months the center moves 

 from a location over the North Pacific Equatorial Water to 

 one over the California Current Extension just east of the 

 Hawaiian Islands. With the onset of fall, the movement is re- 

 versed. Although the center of wind action appears of impor- 

 tance in the seasonal changes in surface water movement, it 

 does not appear to be associated with the time-of-initial- 

 warming index used to predict the availability of skipjack in 

 Hawaiian waters. However, indications are that the time of 

 initial warming is related to the total winter atmospheric 

 circulation pattern of the Northern Hemisphere. This relation 

 is illustrated in the mean sea level pressure charts (fig. 10) 

 for January 1963 and 1964. In 1963 the Asiatic high joined 

 with the North American high, thereby creating a continuous 

 ridge over the polar region and over the eastern Pacific. In 

 1964 the Asiatic, North American, and North Pacific highs 

 appeared as isolated systems separated by pressure troughs. 

 A pattern such as that of 1963 appears to be related to early 

 initial warming of waters around the Hawaiian Islands, while 

 the 1964 pattern appears to be related to late initial warming. 



130° 



ZO" 



NORTH PACIFIC CENTRAL STSTEH^ 



:^± 



170° 



'Vft, 





.JLcl^'si" 



.*^^^ »- . X. 



X XII 



r 8 



NORTH PACIFIC EQUATORIAL SYSTEM 



4 — [___.^a — i — 1_. 4.0- 



150° 



120° 



Figure 9. — Centers of the North Pacific trade- 

 wind system during each month of the year. 



