SECKEL: SKIPJACK AND ENVIRONMENT 



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6- 



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HI 



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 o 



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 z 2 



FF 



FU 



UU 



FF 



FU 



UU 



Figure 2. — Annual skipjack landings in Hawaii grouped 

 according to the temperature and salinity indices being 

 both favorable, FF, one favorable and the other unfa- 

 vorable, FU, and both unfavorable, UU. Panel A: Sa- 

 linity index is favorable with July salinity less than 

 M.^foc. Panel B: Salinity index is favorable with July 

 salinity less than 34.8%c but spring salinity higher than 

 34.6%,. 



tons. The other group comprises the landings 

 in the ¥¥ category that average 5,800 tons and 

 range from 4,940 to 7,330 tons. Landings in 

 the first group occur two-thirds of the time and 

 are normal for Hawaii. Landings in the latter 

 group are clearly exceptional. 



Into which of the two groups landings will 

 fall is in part predictable. The temperature in- 

 dex is determined in April, well before the be- 

 ginning of the summer fishing season. The sa- 

 linity, however, is monitored during spring and 

 has little predictive value. During the 19 years 

 under consideration there have been 4 years 

 when the temperature index was favorable but 

 the salinity was unfavorable. Two of these years 

 were 1968 and 1969, when the spring salinity 

 was the lowest recorded at Koko Head. Thus, 



the temperature index can be used to predict the 

 exceptional fishing years in four out of five cases. 

 This predictability can be improved by subjective 

 interpretation of the salinity trends prior to the 

 fishing season. 



SKIPJACK AND THE TRADE WIND ZONE 

 OCEANOGRAPHY RESULTS 



In the Trade Wind Zone Oceanography (TW- 

 ZO) investigation, oceanographic stations were 

 occupied at fixed locations between lat 10° and 

 26.5°N along long 148°, 151°, 154°, and 157°W 

 at approximately monthly intervals from Feb- 

 ruary 1964 to June 1965 (Figure 3). Although 



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18° 



16' 



14' 



152° 



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150° 



148° W 



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 ''31 



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 -29 



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24" 



22° 



20' 



18" 



16' 



I4< 



150° 148° W 



Figure 3. — Track of the Trade Wind Zone Oceanography 

 cruises. Numbered circles indicate oceanographic sta- 

 tions. 



767 



