DeMartini et al.: Age and growth of Xiphios glodius 



359 



1 and 2 aged specimens used in the inter-laboratory 

 calibration exercise with negligible (<2%) deviation 

 from the majority agreement standard. The age assign- 

 ments of both readers 1 and 2 were henceforth used for 

 growth analyses. If the readers did not agree, reader 2 

 re-examined the specimen to resolve the discrepancy. 

 Specimens with unresolvable ages were omitted from 

 subsequent analysis. 



Age estimates were adequately precise, as well as 

 accurate. CVs of within- and between-reader age es- 

 timates were generally 10-15 9r (Table IB). CVs of 

 the inter-laboratory and main study readings were 

 similar, as were the within- and between-reader CVs 

 within each series (Kruskal-Wallis 1-way ANOVAs; 

 all P>0.3). 



Verification and validation of annul! 



The results of marginal increment analysis (Fig. 1) 

 provided consistent quantitative support for the con- 

 tention that fin rays form a single pair of opaque and 

 translucent bands per year (Campana, 2001). Forma- 

 tion of the annulus is complete by September in cen- 

 tral North Pacific swordfish; MIRs were wider in June 

 and narrower in September (for fish of both sexes) 

 than during the rest of the year (2-way ANOVA on 



sex and month; interaction effect: F=0.80, df=ll,732, 

 P=0.64; month effect: F=2.05, df=ll,743, P=0.02). The 

 pattern generally applied to fish of all ages through 

 at least age-group 7 of adequate sample sizes (Fig. 1), 

 although considerable variability existed throughout 

 the year. 



Verification and corroboration of annuli (Kalish et 

 al., 1995; Campana, 2001) were further explored using 

 several complementary methods. These consisted of 

 comparisons of ages that were based on otolith sagittae 

 and fin rays from matched (same) fish and on quantita- 

 tive relations among fin ray cross-section dimensions, 

 fish body length, and ages based on sagittal DGIs and 

 fin ray annuli. Measurements of total and incremental 

 radii in fin ray cross-sections were obtained for a total 

 1336 swordfish (733 females, range 46-260 cm EFL; 

 603 males, range 36-229 cm EFL). Numbers of DGIs 

 on sagittae were enumerated for a total 63 larval, 

 older juvenile, and small adult swordfish of the two 

 sexes (range 4-135 cm EFL). The EFL-at-age relation 

 was described for 49 fish (range 4-133 cm EFL) for 

 which there were adequately precise DGI counts. Fin 

 ray preparations were available for 50 specimens with 

 matched DGI counts. 



Total cross-section radius of the second ray of the first 

 anal fin was significantly related to fish age in days for 



