ASSESSMENT 



DEVELOPMENT 



MANAGEMENT 



SKIPJACK 

 TUNA 



ABUNDANCE- 



BAIT FISH 



DISTRIBUTION 

 TIME a SPACE 



I I LITTLE DATA 



[ i SOME DATA 



f^]]\ CONSIDERABLE DATA 



-•■ regulations 



♦;PRESENT FISHERIES 



REARING OR HOLDING 

 ANCHOVY 



NEHU 

 OTHERS 



FIELD TRIALS 



Figure 1. — Flow diagram for the development of skipjack fisheries in the central and western Pacific. 



SKIPJACK FISHERY ASSESSMENT 



Abundance 



We will consider those references that attempt 

 to quantify the potential yield of skipjack from 

 the central and western Pacific. These fall 

 generally into three categories: (1) papers and 

 reports coming from Japanese workers, who 

 have concentrated primarily on fisheries near 

 Japan and in the southwestern (south of lat 

 24° N, west of long 160° E) Pacific, (2) papers 

 originating with the Honolulu Laboratory, and 

 (3) papers from the west coast of the United 

 States, chiefly from the Inter-American Tropical 

 Tuna Commission (lATTC). 



The Japanese workers have estimated the 

 potential yield of skipjack in the Pacific in a 

 number of ways based upon current and prewar 

 production and distributional records from their 

 fishing fleet. Estimates for the western Pacific 

 made several years ago include 30,000 metric 

 tons for the Caroline Islands, 15,000 metric tons 

 for Palau (Uchida, 1970), and 150,000-200,000 

 metric tons for the Japanese home island and 

 Ryukyu Islands fishery (based on peak 



landings). No estimates were found for the 

 potential of the New Guinea and Coral Sea 

 grounds, but recently Japanese estimates as high 

 as 1.5-2.0 million tons for the entire Pacific have 

 been made ([U.S.] Bureau of Commercial 

 Fisheries, 1970a; U.S. National Marine Fisheries 

 Service, 1971). 



In the eastern Pacific the lATTC workers 

 (Shimada and Schaefer, 1956; Calkins, 1961; 

 Broadhead and Barrett, 1964; Joseph and 

 Calkins, 1969) have suggested that (1) a 

 considerable tonnage of skipjack are either 

 unexploited or never enter the eastern Pacific 

 fishery, and are located somewhere west of long 

 120° W, and (2) present landings (ca. 50,000 

 metric tons) could safely be increased and 

 perhaps doubled. 



Workers at the Honolulu Laboratory, partic- 

 ularly Rothschild (1966), Silliman (1966), and 

 Rothschild and Uchida (1968), also concluded 

 that there is a large potential yield of skipjack 

 tuna in the central Pacific, their estimates 

 ranging from some 40,000 to over 200,000 

 metric tons on a maximum sustainable yield 

 basis. 



Although all the conclusions are highly 



