DeMartini et al : Age and growth of Xiphios glodius 



363 



Selection of growth model 



Unlike swordfish caught in waters near Taiwan (Sun 

 et al., 2002), swordfish of exploitable size in the central 

 North Pacific near Hawaii grow in length at rates best 

 described by the standard, rather than generalized, 

 VBGF. We suggest that this model primarily reflects the 

 different size structure of catches from the two regions. 

 By truncating the application of our growth model at 

 the approximate minimum size of fish caught by the 

 Hawaii-based longline fishery (60-cm EFL), we eliminate 

 the markedly allometric growth effects that half-year- 

 old and younger fish have on the ascending limb of the 

 VBGF curve. The disproportionately low body mass of 



young juveniles reflects the fact that swordfish, perhaps 

 like most pelagic fishes that are reliant on swimming 

 speed as their primary antipredator adaptation (and 

 unlike typical nonpelagic fish with less pronounced 

 allometric growth), must experience intense selection 

 for growth in length (swimming speed) at the expense 

 of growth in mass during the juvenile stage. A related 

 issue is the fact that swordfish >180-200 cm EFL are 

 more abundant in the Hawaiian than in Taiwanese fish- 

 eries, and these larger fish provide an extended scope 

 for resolving the asymptote of VBGF models, especially 

 the standard VBGF which lacks a fourth parameter 

 (shape function) to help resolve curvature of the ascend- 

 ing limb. Not surprisingly, growth of swordfish caught 



