366 



Fishery Bulletin 105(3) 



finding was confirmed by readers from other laborato- 

 ries during the inter-laboratory exercise. Faster growth 

 in the central North Pacific (versus the western North 

 Pacific) may reflect the high planktonic productivity 

 of swordfish feeding grounds in the Subtropical Con- 

 vergence Zone (Seki et al., 2002), perhaps similar to 

 that in the productive upwelling region off Chile in the 

 eastern South Pacific. Consistent with this observation, 

 data on body condition (weight-at-length) indicate that 

 central North Pacific swordfish are heavier at a given 

 length than swordfish from the western North Pacific 

 (Uchiyama et al., 1999; Sun et al., 2002). Regional dif- 

 ferences in growth rates are also apparent for swordfish 



200 

 180 

 160 

 140 

 120 

 100 

 80 

 60 



240 

 220 

 200 

 180 

 160 

 140 

 120 

 100 

 80 

 60 



1 2 3 4 5 6 7 8 9 10 11 12 13 14 



-T 1 1 



-T 1 1 1 1 r- 



-1 1 r- 



B Females 



Chile (Cerna') 



Pacific Mexico (Castro-Longoria, 1995) 



Taw/an (Sun et al., 2002) 



Hawaii (this study) 



_i 1 I L_ 



1 2 3 4 5 6 7 8 9 10 11 12 13 14 

 Age (yr) 



Figure 6 



Fitted curves describing body length-at-age relationships for 

 (A) male and (B) female swordfish iXiphias gladius) captured 

 by three other regional Pacific fisheries; length-at-age curves 

 for swordfish caught in the region of the Hawaii-based fishery 

 are provided for comparison. To facilitate the comparison, lower 

 jaw-to-fork lengths were converted to eye-to-fork lengths (EFL). 

 EFL-at-age relationships were fitted by using parameters of the 

 standard von Bertalanffy growth formula (VBGF) in all cases 

 except that of Taiwan, for which the generalized VBGF was used, 

 as recommended by Sun et al. (2002). 



throughout the Atlantic and Mediterranean (Tserpes 

 and Tsimenides, 1995; Ehrhardt et al., 1996; Alicli and 

 Gray, 2001). 



Stock structure is still incompletely understood for 

 Pacific swordfish and regional variations in growth 

 rates complicate rather than resolve the issue. Pres- 

 ent understanding of the population genetics of sword- 

 fish indicates that separate stocks exist in the North 

 and South Pacific and that there likely is some stock 

 structuring between east and west in the North Pacific 

 (Reeb et al., 2000). Detailed comparisons among the 

 nuclear (microsatellite) DNAs and mtDNAs of plank- 

 tonic spawning products (eggs and larvae) and fish of 

 exploitable sizes, coupled with analyses of phe- 

 notypic traits like growth and environmental 

 markers, such as trace element signatures in 

 otoliths (Humphreys et al., 2005), are needed 

 for swordfish collected from all regional fisher- 

 ies in order to fully resolve the stock issue for 

 swordfish in the Pacific. 



Acknowledgments 



We gratefully acknowledge C.-L. Sun (National 

 Taiwan University), K. Yokawa (National 

 Research Institute of Far Seas Fisheries), O. 

 Sosa-Nishizaki (Centro de Investigacion Cien- 

 tifica y de Educacion Superior de Ensenada), 

 and F. Cerna (Instituto de Fomento Pesquero) 

 for their cooperation in implementing the inter- 

 laboratory calibration exercise mandated at 

 the Second Meeting of the Interim Scientific 

 Committee for Tuna and Tuna-like Fishes in 

 the North Pacific (ISC2) held January 15-23, 

 1999, in Honolulu, Hawaii. We also thank M. 

 McCracken for statistical advice, D. Yamaguchi 

 for assistance with preparing all of the final 

 figures, and P. Kleiber, D. Kobayashi, R. Nishi- 

 moto, C. Boggs, and three anonymous review- 

 ers for constructive criticisms of a draft of the 

 manuscript. 



Literature cited 



Alicli. T. Z., and I. K. Gray. 



2001. Age and growth of swordfish (Xiphias 



gladius L., 1758) in the eastern Mediterranean 



Sea. Int. Comm. Conserv. Atl. Tunas, Coll. 



Vol. Sci. Pap. 52:698-707. 



Arocha, F., C. Moreno, L. Beerkircher. D. W. Lee, and 



L. Marcano. 



2003. Update on growth estimates for sword- 

 fish, Xiphias gladius, in the northwestern 

 Atlantic. Int. Comm. Conserv. Atl. Tunas, 

 Coll. Vol. Sci. Pap. 55(4):1416-1429. 

 Berkeley, S. A., and E. D. Houde. 



1983. Age determination of broadbill swordfish, 

 Xiphias gladius, from the Straits of Florida, 

 using anal fin spine sections. NOAA Tech. 

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