lie to the northwest and west of Australia; no 

 bluefin occur in peripheral areas and few on the 

 grounds outside of the September-April season. 

 The catches differ in that there are two catch 

 peaks on the Old Ground and one on the New, 

 and the Old Ground fish are large through the 

 season whereas the New Ground fish are small 

 at the season's peak. The fish on both grounds 

 are thought to be spawning groups. 



Greatest food consumption occurred at the first 

 feedings early in the day, and smaller amounts 

 were eaten through the remainder of the day. 

 Shrimp exoskeletons begin to occur in the feces 

 about 1. 5 hours after a meal at 74° F. They ate 

 little or nothing after dark and would not take 

 food particles from the bottom of the pool. The 

 size of food particles they would eat decreased 

 as they became satiated. 



Nakamura, Eugene L. 



Nakamura, Hiroshi 



The establishment and behavior of skip- 

 jack tuna (Katsuwonus pelamis) in 

 captivity. /Conference Paper IV - 2.J 



Skipjack tuna (2-6 pounds) were success- 

 fully maintained in an outdoor pool for 5-1/2 

 months at the Kewalo Basin docksite laboratory 

 of the Bureau of Commercial Fisheries Biolog- 

 ical Laboratory at Honolulu. The circular pool, 

 4 feetdeep and23 feet in diameter, was supplied 

 with 50 gallons of oxygenated salt water per min- 

 ute. Successful establishment was achieved by 

 transferring the fish from the place of capture 

 to the shore pool in a portable tank. The port- 

 able tank contained 620 gallons of water and, 

 while on the vessel, was supplied with 100 gallons 

 of new water per minute. Skipjack were caught 

 by pole-and-line , lowered into the portable tank 

 and allowed to shake out the barbless hook. On 

 shore the portable tank was lowered into the pool, 

 and the skipjack were allowed to swim out. The 

 fish fed in captivity, and recovered from minor 

 wounds received at capture. After 4 months one 

 fish had sunken eyes, but could still feed. 



Skipjack swim with their mouths agape, 

 and erect their first dorsal and pectoral fins 

 when turning. All fins are erected to maximum 

 extension when the fish decelerate s u d d e n 1 y. 

 They demonstrate no rheotaxis. They schoolin 

 captivity, but schooling is disrupted when food 

 is presented. While the tuna are feeding or when 

 they are presented with a food stimulus, verti- 

 cal bands appear ontheir dor sal lateral surface. 

 When the fish were trained to associate a slap 

 on the water surface with food, the appearance 

 of vertical bars could also be elicted by the slap 

 alone. After the tuna had fed to satiation these 

 responses did not occur. When not in a feeding 

 state, the tuna is marked with horizontal bars 

 on the latero-ventral surfaces. Other noticeable 

 colorations are the silvery tongue and the lead- 

 ing white spine in the first dorsal fin. 



When fed to satiation once a day they 

 ate 1.6 ounces of squid and shrimp per pound of 

 skipjack per day, but when fed 13 times per day 

 this increased to 3.2 ounces per pound per day. 



An outline of the tuna longline grounds 

 in the Pacific. /Conference Paper 



I - 17 



The Pacific Ocean is characterized by a 

 series of current systems extending in an east- 

 west direction. These systems are distinct en- 

 vironments and have distinctive fisheries, for 

 example, the North Pacific Current north of 28° 

 is noted for its albacore, while part of the South 

 Equatorial Current is conspicuous for yellowfin. 

 In addition to stratification by current systems, 

 the fisheries show east-west gradients in length 

 composition, as well as variations in amount of 

 catch per unit of fishing effort. There is an over- 

 all tendency for tuna and marlin catches to be 

 heavier in the Southern Hemisphere than in the 

 Northern Hemisphere. 



Otsu, Tamio, and Richard J. Hansen 



Sexual maturity and spawning of albacore 

 in the central South Pacific Ocean. 

 /Conference Paper VII -Z.J (In press 

 as U. S. Fish and Wildlife Service, 

 Fishery Bulletin 204, vol. 62.) 



Developmental stages of gonads of the 

 albacore, Thunnus germo (Lacepede), taken in the 

 central South Pacific Ocean by Japanese and 

 South Korean longline vessels based in American 

 Samoa were studied. The samples comprised 

 782 pairs of ovaries and 990pairs of testes col- 

 lected from 256 landings between August 1957 and 

 September 1958. 



Occurrence of ova in late stages of de - 

 velopment indicates that the South Pacific alba- 

 core spawn during the southern summer, between 

 September and March, as opposed to the northern 

 summer spawning of the North Pacific albacore. 

 This difference in spawning periods is believed 

 to constitute evidence that the stocks of albacore 

 in the South Pacific and the North Pacific are 

 independent of each other. The data suggest that 

 the bulk of the spawning activity is confined to 

 the area between the Equator and latitude 20° S. 



32 



