22 



Fishery Bulletin 92(1), 1994 



Males 



H3— 

 -B- 



100 



Females 



200 



Mil) 



Females 



200 



did 



Kill 



500 



100 200 300 



MANTLE LENGTH (mm) 



)(i( i 



200 300 

 AGE (days) 



Figure 8 



Relationship between mantle length and number of increments in sta- 

 toliths and male and female maturity stage: western North Pacific (open 

 circles), central North Pacific (closed circles), and eastern North Pacific 

 (open squares). Ranges are represented by horizontal bars. 



active oceanic squids (e.g., Onychoteuthidae, 

 Ommastrephidae) may require substantial mainte- 

 nance facilities to support long-term survival. 



Although the rate of increment deposition derived 

 by the statolith marking experiment should be con- 

 sidered preliminary, indirect evidence was obtained 

 to suggest that increments were formed daily. The 

 hypothesis that the lifespan is 1 year (Murata and 

 Ishii, 1977; Naito et al., 1977b) was supported by the 

 present data where only 4 of the 126 individuals 

 aged had more than 365 increments within the sta- 

 tolith. In addition, back-calculated hatch dates 

 (July-February) of post-recruit individuals exploited 

 in the O. borealijaponica jig and Ommastrephes 

 bartramii squid driftnet fishery were consistent with 

 information on spawning (fall-winter) reported in 

 the literature (Murata et al., 1976; Murata and Ishii, 

 1977; Naito et al., 1977b). This study suggests that 

 spawning for O. borealijaponica occurs year round. 

 While subadult O. borealijaponica are distributed in 

 subarctic waters, evidence from the distribution of 

 paralarvae, juveniles, and sexually mature females 

 suggests that spawning may occur to the south of 

 the subarctic boundary in the North Pacific transi- 

 tion zone (30^42°N, terminology after Roden, 1991). 

 In the central and eastern North Pacific, O. 

 borealijaponica paralarvae and juveniles have been 

 recorded from this study (38°N, 179°30'W°) and the 



coast of California (~33°N, Young, 

 1972), respectively. In the western 

 North Pacific, spawning may oc- 

 cur in waters of the Kuroshio Cur- 

 rent and Kuroshio Countercurrent 

 (Murata and Ishii, 1977; Naito et 

 al., 1977a) or between the Kuro- 

 shio and Oyashio fronts. Onycho- 

 teuthid paralarvae have been cap- 

 tured from both the Kuroshio Cur- 

 rent and Kuroshio Countercurrent 

 (Okutani, 1968, 1969, 1975); how- 

 ever, distributional evidence is in- 

 conclusive because of the taxo- 

 nomic uncertainties of the speci- 

 mens captured. Spawning may 

 occur in the transitional area be- 

 tween the Kuroshio and Oyashio 

 fronts, as sexually mature and 

 copulated females have been cap- 

 tured off Hokkaido, Japan (42°30TSJ, 

 150°40'E and 42°15'N, 144°25'E, 

 Murata et al., 1981). 



The ML-weight relationships 

 obtained in this study for the 

 western, central, and eastern 

 North Pacific were similar to the 

 values previously given for O. borealijaponica cap- 

 tured off Japan (Murata and Ishii, 1977). Slope val- 

 ues obtained for the ML-weight relationships 

 (males=2.596, females=2.915) were similar to other 

 active oceanic squids having thick muscular mantle 

 walls. Paralarval O. borealijaponica had a higher 

 slope value (3.015) than older males and females, 

 consistent with previous results for loliginid squids 

 and benthic octopods (Forsythe and Van Heukelem, 

 1987). 



There is no clear consensus on the type of model 

 which best describes cephalopod growth, although 

 several studies argue against the use of asymptotic 

 models, such as Gompertz or von Bertalanffy 

 (Forsythe and Van Heukelem, 1987; Saville, 1987). 

 Exponential models have been typically used to 

 describe the growth of field caught and laboratory 

 reared paralarval squid (Yang et al., 1986; Balch et 

 al., 1988; Forsythe and Hanlon, 1989; Bigelow, 1992, 

 1993). For growth estimates derived from statolith 

 analysis, a linear model is frequently used because 

 growth is analyzed over a short segment of the 

 cephalopod's life history, such as post recruitment 

 to a fishery (Rosenberg et al., 1980; Radtke, 1983; 

 Rodhouse and Hatfield, 1990b) or habitat (Jackson 

 and Choat, 1992). 



Since the Schnute model encompasses a wide 

 range of growth models, it can be used to system- 



