AbStTclCt.— Length-frequency 

 data, vertebral-ring-counts, and 

 length measurements of tagged fish 

 were analyzed to independently es- 

 timate von Bertalanffy growth pa- 

 rameters for south Pacific albacore 

 {Thunnus alalunga). As a working 

 hypothesis, we assumed that the 

 length-frequency modes and verte- 

 bral-rings are annual features. The 

 MULTIFAN model fitted to length- 

 frequency data provided estimates 

 of L and K of 97.1cm and 0.239 

 year 1 , respectively. Nine age classes 

 were detected in the data. Growth 

 varied seasonally: growth rate de- 

 creased to almost zero during Au- 

 gust and peaked during February. 

 Two to thirteen rings were visible in 

 the vertebrae, and estimates of L 

 and A' of 121.0 cm and 0.134 year 1 , 

 respectively, were obtained. No sig- 

 nificant differences in growth param- 

 eters were detected between males 

 and females. The growth rates pre- 

 dicted by the length-frequency and 

 vertebral-ring-count models were 

 very similar throughout the range 

 of presumed age classes present in 

 both data sets. These growth rates 

 were consistent with length incre- 

 ment observations from 28 tag re- 

 turns, which lends support to our 

 assumptions of annual vertebral- 

 rings and length-frequency modes. 



Determination of age and growth 

 of South Pacific albacore 

 (Thunnus alalunga) using three 

 methodologies 



Marc Labelle 

 John Hampton 



Tuna and Billfish Assessment Program 



South Pacific Commission. Noumea, New Caledonia 



Kevin Bailey 

 Talbot Murray 



Ministry of Agriculture and Fisheries 

 Fisheries Research Center, PO. Box 297 

 Wellington, New Zealand 



David A. Fournier 

 John R. Sibert 



Otter Research Ltd , Box 265, Station A 

 Nanaimo. B C, Canada 



Manuscript accepted 5 July 1993. 

 Fishery Bulletin 91: 649-663 (19931. 



Albacore (Thunnus alalunga) have 

 been fished in the south Pacific by 

 Japanese longliners since 1952, and 

 by Korean and Taiwanese longliners 

 since 1958 and 1963, respectively 

 (Wang, 1988). Japanese longliners 

 ceased targeting albacore in the mid- 

 1960's, but longline fishing for alba- 

 core by Korean and Taiwanese fleets 

 has continued. Since 1960, annual 

 longline catches have fluctuated be- 

 tween 25,000 metric tons (t) and 

 40.000 1 (Anonymous, 1991). In the 

 1980s, a surface fishery for juvenile 

 albacore developed, comprising drift 

 gillnet vessels from Japan and Tai- 

 wan and troll vessels mainly from 

 the United States, New Zealand, Fiji, 

 and French Polynesia. By 1989, the 

 annual surface-fishery catches of al- 

 bacore had reached about 30,000 t 

 (Anonymous, 1991). The rapid expan- 

 sion of the surface fishery catalyzed 

 concerns over potential overfishing 

 and possible effects on longline catch 

 rates of larger albacore. This in turn 

 highlighted the need for detailed in- 

 formation on the fisheries and on the 

 dynamics of the albacore population. 



Investigations of albacore biology 

 have been conducted since 1985 by 

 scientists from the United States, 

 France, New Zealand, and the South 

 Pacific Commission. The goal of this 

 research has been to obtain informa- 

 tion on a range of biological and 

 fishery-related processes, including 

 growth, catch age structure, stock 

 structure, and mortality. Albacore 

 catch rates and size composition in 

 the troll and drift gillnet fisheries 

 have been monitored through a 

 fishery observer program since 1988 

 (Hampton et al., 1989, 1991; Sharpies 

 et al., 1991; Labelle, 1993a). Alba- 

 core tagging programs were estab- 

 lished in 1986 to provide information 

 on movement, mortality, growth and 

 approximate stock boundaries (Anon., 

 1986; Pianet et al., 1990; Labelle, 

 1993b). Catch sampling at major 

 landing sites has been carried out to 

 monitor catch size composition, to col- 

 lect logbook data, and to obtain 

 samples of bony structures and go- 

 nads for estimation of growth rates 

 and spawning periodicity. Estimates 

 of growth rates, and, in particular, 



649 



