THE TUNAS OF THE CENTRAL PACIFIC 



Three fisheries at present harvest the tunas of the central 

 Pacific, that part of the great ocean lying west of about 

 lat. 130° W. and east of the date line. By far the largest 

 catches are made by the Japanese longline fleet, which has 

 operated in the area since the mid-li)50's. The other two 

 fisheries are the Hawaiian pole-and-line fishery for the skip- 

 jack tuna and the Hawaiian longline fishery for the larger, 

 older tunas of the ocean depths (fig. 2). 



On the eastern edge of the Pacific Basin is still another 

 tuna fishery, that conducted along the shores of the Americas 

 by the fleet based in California. This is the richest of 

 American tuna fisheries and one of the largest in the world. 

 Biologists have shown that some of the skipjack tuna caught 

 off the Americas are closely linked to those of Hawaii: the 

 relation between the two fisheries may be very close. 



The Hawaiian fishery is small. Eager that it should con- 

 tribute more strongly to the Hawaiian economy, the State 

 has enthusiastically supported the eff'ort of the BCF Lab- 

 oratory in Honolulu to estimate the true potential of the 

 central Pacific. This reporting period has brought the first 

 numerical estimates of the resources. 



The State of the Hawaiian Fisheries 



Hawaiian skipjack tuna landings reached record heights 

 in 196.5. More than 8,000 tons were taken, more tuna than 

 the combined pole-and-line and longline fleets usually take in 

 an average year. Fishermen who in ordinary years had to 

 content themselves with an income of about $5,000 made 

 $10,000 and upward in 1965. The bonanza ended in January 

 1966, as abruptly as if a door had slammed; skipjack tuna 

 landings reached only 68 percent of those in January of the 

 previous year. The summer season of 1966 was disappoint- 

 ing, and the .vear as a whole was barely average. 



On the basis of the change in the rate of warming of the 

 .sea surface at Koko Head (fig. .3), southernmost point of 

 the island of Oahu, on which Honolulu is situated, Gunter 

 R. Seckel of the BCF Laboratory in Honolulu was able to 

 warn in April that catches for 1966 would remain at or below 

 average. When the surface water begins its seasonal warm- 

 ing early in the year and when "favorable" water of low 

 .salinity bathes the islands during the summer, the aku catch 

 soars. Neither condition prevailed in 1966. 



Seckel says, "We have found that two environmental 

 indicators can be related to fishing that is better than aver- 

 age. The first is when the change of winter cooling of the 

 surface water to spring warming occurs in February rather 

 than in March. The second is when waters bathing the 

 islands during the fishing season have a salinity of less than 

 34.8'-- . The first index, since it occur:; in February or 

 March, is of predictive value with respect to the main aku 

 season during the summer. 



"In 1966 the initial warming took place in March and 

 therefore indicated a fishing season with below average 

 availability of skipjack tuna." This prediction was borne 

 out by the catch. 



Some evidence suggests that the island of Hawaii lay in 

 the path of the "favorable" waters during the summer of 

 1966 and that catches there were above average, but the 

 bulk of the fleet is based to the northwest on the island of 

 Oahu. 



Although the skipjack tuna fishery boomed in 1965, and 

 had at least an average year in 1966, Hawaii's other large 

 fishery, that based on the longline, demonstrated no such 

 striking alternations in fortune. In 1965, the longline 

 ves.sels took about 630 tons of tunas; their catch of billfishes 

 brought their total landings to about 925 tons. 



