150 EIGHTH PACIFIC SCIENCE CONGRESS 



sardine catch is due to fishing, and how much is to be attributed to 

 changes in the oceanic environment; but there seems to be no question 

 that the populations of this species have no possibility of supporting 

 a much greater catch than has been attained in the past. The herring 

 fisheries of the North Pacific, on both sides of the ocean, seem to be 

 rather fully exploited. The great Japanese trawl fisheries of the East 

 China Sea and adjacent areas have been so heavily fished that they are 

 now subject to regulation to curtail the intensity of fishing. Certainly 

 there are yet demersal and inshore fish stocks that are little utilized, 

 such as the hake and pollock of the Northeastern Pacific. In the main, 

 however, the new frontier of commercial fishing is the exploitation of 

 the oceanic fishes of the high seas. 



The potential food production from fisheries of the high seas is 

 doubtless very large. The cost of harvesting this crop is, however, also 

 large. Under present economic circumstances, therefore, development 

 of high sea fisheries is confined to those species which occur in high 

 local concentration and have a relatively high unit value, so that the 

 catch per unit of fishing effort has sufficient value to offset the high cost 

 of production. Few pelagic oceanic organisms meet these requirements 

 at the present time. The whales are, of course, an outstanding example. 

 Among the fishes, the tunas support one of the few major fisheries of 

 the high seas in the Pacific. The several species of tunas aggregate in 

 sizable schools, occur in relatively large concentrations in certain areas 

 of the sea, and command a high market price. They have, therefore, 

 become the object of increasingly extensive and intensive fisheries. 



Tuna Fisheries of the Pacific 

 Five kinds ot tunas are the objects of important commercial fish- 

 eries in the Pacific. They are: 



Alhacore—Thunnus germo 

 YellowUn—Neothunnus macropterus 

 Skipiack—Katsuwonus pelamis 

 Bigeye—Parathunnus sibi 



"EAuehn—Thunnus thynniis, T. orientalis, T. maccoyi 

 Several other species support fisheries of a local nature and of 

 minor importance, including Kishinoella tonggol, the northern bluefin 

 of Australia, and the several species of Euthynnus. The bonitos, genus 

 Sarda, which support important fisheries, are not usually considered 

 tunas in the strict sense. 



The fisheries for tunas in the Pacific have developed rapidly dur- 

 ing the last three decades, and at present are among the most valuable 

 fisheries of this ocean. In the United States, the tunas rank first in 



