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Fishery Bulletin 94(4). 1996 



Materials and methods 



Albacore were sampled from the catches of two 

 longline vessels: a Japanese-New Caledonia joint- 

 venture with longliners fishing in New Caledonia 

 waters (21°-23°S, 164°-166°E) and unloading in 

 Noumea, and 2) the Tonga government-owned 

 longliner, MV Lofa, operating in Tonga waters (16°- 

 29°S, 171°-177°W) (Fig.l). These sampling arrange- 

 ments were selected because these vessels fished 

 throughout the year in known spawning areas. Fish- 

 ing operations took place during daylight and stan- 

 dard commercial longline gear was used. 



Sampling was designed to cause minimum distur- 

 bance to commercial operations while providing ad- 

 equate samples and data. For both sampling opera- 

 tions, sex, fork length (to the nearest centimeter), 

 and gonad weight (to the nearest g, New Caledonia 

 [females]; or to the nearest 5 g, Tonga [females and 

 males]) were measured. In waters near New 

 Caledonia, ovaries from each 10-cm size class (70- 

 79 cm, 80-89 cm, 90-99 cm, and 100-110 cm) were 

 collected each collection day, but actual quantities 

 were dependent on the landings from the commer- 

 cial operation. However, in waters near Tonga, ova- 

 ries were collected only from albacore in the 80-89 

 cm size class because of sampling limitations. Sam- 

 pling in waters near New Caledonia was done once a 



week, May 1990 to February 1992, whereas sampling 

 near Tonga occurred on every second set of the 

 longline during January 1990 to February 1992. 



In New Caledonia and aboard Lofa, gonads were 

 removed from the gut cavity of albacore and identi- 

 fied as male or female. Each pair was separated into 

 a left and right section and weighed fresh to the near- 

 est 1 g in New Caledonia and to the nearest 5 g on 

 Lofa for size comparison. Weights of fresh gonads 

 included the weight of the associated fatbody. 



A total of 1,105 albacore were examined and mea- 

 sured (300 females, 799 males, 6 undetermined); of 

 this number, 246 pairs of ovaries and 444 pairs of 

 testes were weighed fresh (Table 1). A subset of 150 

 ovaries were collected from female albacore in vari- 

 ous stages of development for histology. A greater 

 percentage of the ovaries collected came from New 

 Caledonia because ovary collections from waters near 

 Tonga were limited to ovaries from albacore in the SO- 

 SO cm FL size range. In the laboratory, the ovary was 

 removed from a formalin fixative, patted dry, and 

 weighed to the nearest 0.1 g. The associated fatbody 

 was then removed and the ovary reweighed without 

 the fatbody; these values were then used to calculate 

 the gonadosomatic index (GSI). Male albacore testes 

 were not collected for histological study from either site. 



Histological processing was done by staff at the 

 Maas Diagnostic Laboratories who followed the 



Figure 1 



Sampling areas for albacore, Thunnus alalunga, in the South Pacific Ocean 

 near New Caledonia and Tonga from 1990 to 1992. 



