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Fishery Bulletin 92(4). 1994 



significantly greater than for the shallow group on 

 five of nine cruises (Mann-Whitney U-test, P<0.05) 

 with similar, nonsignificant trends seen on three ad- 

 ditional cruises (Table 2). These differences were 

 greatest in summer. There was no apparent trend in 

 size with depth for females (Table 2). 



Age and growth 



Spine increments were counted for 102 males (20.8- 

 72.2 cm TL) and 105 females (20.6-79.5 cm TL). Incre- 

 ment counts ranged from to 27 for female spines and 

 to 18 for male spines. Mean length at age for each sex 

 was similar up to age 9; thereafter, females grew faster 

 (Fig. 4). For both sexes, the mean length at time was 

 greater than that expected based on the estimated size 

 at parturition for S. mitsukurii (see Reproduction). 



Fitted growth curves for each sex differed consid- 

 erably (Fig. 4). The L m estimate for females exceeded 

 the observed maximum length from the catch data 

 (i.e. 91 cm), although the L^ estimate for males was 

 much lower than the observed value of 82 cm. 



Reproduction 



Reproductive data were collected from a total of 258 

 female S. mitsukurii specimens during 1986-88. 

 Gravid females examined during the four seasons 

 ranged from 61 to 80 cm TL. The estimated size at 

 50% sexual maturity for females was 69 cm (Fig. 5). 

 This size corresponds to an age of about 15 years. 

 The largest infertile or sexually inactive female was 

 88 cm. No differences were found in the depth distri- 

 butions of gravid and nongravid females greater than 



