360 



Fishery Bulletin 105(3) 



older juveniles and small adults (Fig. 2). The best fitted 

 power equation relationship: 



i?j„, = 0.0197 DGI o™77^ 



0.877, 



predicted an R^^^ of 2.055 ±0.069 (mean ±SE) mm at an 

 age of 365 days. For a larger sample of fish aged to be 1 

 yr old by using fin rays, the radius i?j (the just-completed 

 first annulus) was 2.23 ±0.091 mm from the focus on 

 cross sections cut as described and was unrelated to sex 

 offish (Students <=0.88; «=71 fish; P=0.38). 



Cross sections taken at the suture terminus were 

 located about 14% of the conforming total length (distal 

 surface) of the ray above the condyle. In a comparison 

 between cross sections from matched (same) fish, where 

 the cross sections were taken at our suture terminus 

 and the d/2 position for 115 specimens (sexes pooled) 

 ranging from 82-241 cm EFL, the conventional cross- 

 section radius was located at a shorter average distance 

 (about 10%) above the condyle. Total radii of cross sec- 

 tions produced by the two different types of cuts nec- 



0.6 



0.5 



0.4 



!? 0.3 



A Males 

 30 41 



23 



34 

 O 



I I 29 IZ 



33 



36 



32 



19 



25 



22 



^ 0.7 



0.6 



05 



0.4 



- B Females 26 



3 4 



6 7 

 Month 



9 10 11 12 



Figure 1 



Monthly means of the marginal increment ratio (MIR) 

 for (A) male and (B) female swordfish iXiphias gla- 

 dius) caught in the region of the Hawaii-based pelagic 

 longline fishery during 1993-97. Vertical lines indi- 

 cate ±1 standard error (SE). Number offish specimens 

 is noted above each monthly estimate. Code to months: 

 1 = January, 2 = February, ... 12 = December. 



essarily differed slightly (by 3%; ANCOVA; P<0.001) 

 but were independent of fish size and sex (ANCOVA; 

 P=0.6 and 0.3, respectively). Despite these numeric 

 differences, there was no discernible average differ- 

 ence in annuli counts with sections cut at the suture 

 terminus and dl2 positions. Core regions of basal cut 

 sections were obscure in 77% of the specimens whose 

 ages ranged from 1 to 11 years (ages estimated by using 

 suture terminus sections). Either the first annulus was 

 missing or the section could not be aged for 21% of the 

 basal cut specimens. Ages averaged 0.8 yr younger with 

 basal sections (matched-pairs signed-ranks test; P<0.01) 

 for 25 of the specimens whose age estimates differed 

 between basal and distal sections, and averaged 0.2 yr 

 younger overall. For basal cuts only, mean back-calcu- 

 lated body lengths at age 1 yr, based on the presumed 

 "first annulus," differed in predicted fashion among age 

 groups (i.e., they were greater for older fish in which the 

 real first annulus was more apt to be missing with age 

 (2-way ANOVA on age-group and type of section; age- 

 group effect: P<0.0001; Penha et al., 2004). 



Daily growth of young swordfish based on counts of 

 DGIs on otoliths strongly corroborated our estimates of 

 size-at-age for age-group (age O-i-) and yearling fish 

 based on fin ray cross sections (Fig. 3). Body length 

 was nonlinearly related to presumed age in days and 

 the most parsimonious, best fit was the hyperbolic, two- 

 parameter relation: 



EFL = (136.6 DGI) / (140.8 -i- DGI), ^2 = 0.937, n = 49. 



This best fit relation indicated a body length of 98.6 ±3.0 

 (95 % CI) cm EFL at an age of 365 days (Fig. 3). 



Development of growth model 



The relations between EFL and cross-section fin ray 

 radius were strongly curvilinear, and doubly log-trans- 

 formed data differed in elevation for females and males 

 (ANCOVA: F^ 1333 = 6.41; P=0.01) but shared a common 

 slope (ANCOVA; Fj 1332=0.84; P=0.36). For R^^^ measured 

 in mm and EFL (in cm), the best fit relations were 



Females EFL = 64.3725 R^^^ « 5539^ ^2^o.939; 

 Males EFL = 66.3090 R^^^ ".^its^ ^2=0.936. 



/fjQj regressed on EFL indicated that Pi should be 

 about 2.16 mm, using the independent length-at-age 1- 

 yr estimate of 98.6 cm EFL. An Pj of 2.055 mm would 

 be equivalent to a length of about 96 cm EFL (Figs. 2 

 and 3). 



Table 2 lists our sex-specific, back-calculated EFL-at- 

 age estimates. Summary statistics for the corresponding 

 estimates of ray radii are provided in Table 3 for males 

 and females, respectively, by age group and averaged 

 over all age groups. We estimated an age of 0.58 yr (213 

 days) at an observed mean EFL of 82.2 cm from the oto- 

 lith-based length-at-age relation (Fig. 3) and used this 

 estimate to represent the mean length of age-group-0 

 fish 2:60 cm EFL in the aged population. 



