Bigelow Age and growth of Onychoteuthis borealijaponica 



of western North Pacific males or eastern North Pa- 

 cific males and females. 



Results 



Statolith analysis 



Statolith microstructural analysis was applied to 

 131 squid from the western, central, and eastern 

 North Pacific. Five statoliths (3.8%) were broken or 

 poorly sectioned and excluded from further analy- 

 sis. The coefficient of variation about the mean for 

 the aged samples (n = 126) averaged 3.7% based on 

 2-3 increment counts for each statolith. No obvious 

 trend existed in the coefficient of variation with the 

 increment count or body size. 



Periodicity of increment formation 



A fluorescent OTC band was evident in the sta- 

 toliths of the three squid exposed to oxytetracycline. 

 While increments peripheral to the inner edge of the 

 OTC band could not be reliably counted, the rela- 

 tion between the growth of the statolith, rearing 

 period, and the width of increments prior to the OTC 

 band suggested that increments were deposited 

 daily (Table 2). Statolith growth in the dorsal dome 

 region ranged from 1.4 to 4.3 urn over the rearing 

 period (26-61.5 hr). The average number of incre- 

 ments deposited per day after oxytetracycline expo- 

 sure was 1.30 (range 1.08-1.52) for the three squid. 



Mantle length-weight relationships 



The ML-weight relationship for paralarval O. 

 borealijaponica from the central North Pacific is 

 represented by the equation 



WT = 2.484 x 10" 5 ML 3015 ;fl 2 = 0.99(n = 36). 



(4) 



The ML-weight relationships for juvenile-adult O. 

 borealijaponica from the western, central, and east- 

 ern North Pacific are represented by the following 

 equations: 



males: 



WT = 1 .873 x lO^ 4 ML 2596 ;J? 2 = 0.96(n = 43) (5) 

 females: 



WT = 3.521 x \0- ML 2SX5 ;R 2 = 0.99(n = 68) (6) 



The slopes of the ML-weight regressions for male 

 and female O. borealijaponica were significantly 

 different (P<0.001). 



Growth 



A good relationship existed between the number of 

 increments within statoliths and squid size for in- 

 dividuals in the central North Pacific (Fig. 5). An 

 exponential model (Table 3, Equation 7) was appro- 

 priate to describe the ML-at-age relationship 

 (f-1.82, F=2A9) for females (paralarvae-subadult) in 

 the central North Pacific. A logistic model was ap- 

 propriate to describe the ML-at-age relationship 

 (f=1.85, f=2.93) for males (paralarvae-adult) in the 

 central North Pacific. However, the oldest individual 

 (394 days, 245 mm ML) was a mature male (stage 

 V) which influenced the type of model selected. 

 Omitting that individual resulted in the selection of 

 an exponential model (f=2A9, F=2.55) over a logis- 

 tic model (/"=4.73, F=2.94) to describe paralarval- 

 subadult growth (Table 3, Equation 8). Exponential 

 models were also fit to weight-at-age data for 

 paralarval-subadult males and females (Table 3, 

 Equations 9 and 10). 



Growth in length (% increase in length per day) 

 was similar for males and females (0.80% ML/day) 

 in the central North Pacific, while growth in weight 

 was faster for females (1.90% WT/day) than males 

 (1.40% WT/day). By using the exponential models, 

 mantle length, weight-at-age, and absolute growth 



