Chiang et al.: Age and growth of Istiophorus platypterus in waters off eastern Taiwan 



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 Ring number 



Figure 4 



Mean (±1 SD) ring radius for male and female sailfish (/. platypterus) collected 

 from the waters off eastern Taiwan that had at least the first or second ring 

 present. The numbers above the vertical bars are the sample sizes. 



may also be related to sailfish migration and environmen- 

 tal factors, as suggested by Sun et al. (2002) for swordfish. 

 The MIR analysis provides only a partial age validation; 

 complete validation requires either mark-recapture data 

 or the study of known-age fish (Beamish and McFarlane. 

 1983; Prince et al., 1995; Tserpes and Tsimenides, 1995; 

 Sun et al., 2001, 2002). 



Selection of a growth curve 



Female sailfish are typically larger for similar ages in 

 males and grow faster than males, and the length-weight 

 relationship differs significantly between the sexes. 

 Similar results have been reported for east Pacific Ocean 



sailfish (Hernandez-Herrera and Ramirez-Rodriguez, 

 1998 ). Indian Ocean sailfish (Williams, 1970 ) and Atlantic 

 Ocean sailfish (Beardsley et al., 1975; Jolley. 1974, 1977; 

 Hedgepeth and Jolley, 1983). 



The Richards function appears to fit the data better 

 than the standard VB curve (Fig. 8) and provides a more 

 realistic description of growth for animals of age 0. The 

 standard VB curve is commonly used to describe asymp- 

 totic growth in fish but did not fit the back-calculated 

 lengths for fish younger than three (Table 4, Fig. 8). 



Further discussion of growth curves will likely focus 

 on method 2 (i.e., a power function relationship between 

 spine radius and LJFL) because it provides a better fit to 

 the data than method 1. Ehrhardt (1992), Ehrhardt et al. 



