10 



Fishery Bulletin 94(1), 1996 



The proportion of maturing females increased dur- 

 ing the summer; this group predominated in catches 

 (70%) in August-September. In October, maturing 

 females decreased rapidly in numbers and almost 

 disappeared in November. Their size range gradu- 

 ally narrowed from 170-320 mm in June to 210-280 

 mm in November. The length composition of matur- 

 ing females was unimodal. Their modal classes re- 

 mained constant (240-250 mm) from June to August, 

 then increased slightly to 260 mm in September- 

 October. 



Mature females were predominant among females 

 in June (53%). Subsequently their numbers de- 

 creased constantly until September (20%), then in- 

 creased abruptly in October-November (70%). 

 Length composition of mature females was always 

 unimodal and wide (180-370 mm). Their modal 

 lengths did not change from June to August (250- 

 260 mm), but increased slightly in September-No- 

 vember (260-270 mm). The proportion of mature fe- 

 males that had mated was very high during June- 

 August (86—90%), then diminished considerably by 

 the beginning of October (34% ). The numbers of spent 

 females were low from June to September (<2%). In 

 October, they almost vanished from catches, appear- 

 ing again in November (5%). Their size range was 

 wide (220-330 mm) with an indistinct mode at 240- 

 250 mm. 



Juvenile abundance was greatest in June— July and 

 diminished successively until November. The length 

 composition for this group varied greatly through- 

 out the period of study, with one distinct modal size 

 in June ( 80-90 mm ), two in July ( 30 mm and 70 mm), 

 one in August and September ( 100 mm and 110 mm, 

 respectively), and two in October (60 mm and 

 119 mm). 



Navarin-St. Matthew region In the Navarin-St. 

 Matthew region (Fig. 5), immature and maturing 

 males were most abundant in June (22% and 44%-, 

 respectively). They decreased progressively in num- 

 ber from July to September and almost disappeared 

 in October (about 3% each). The largest immature 

 specimens were 190-200 mm ML. Their size compo- 

 sition was unimodal (160-170 mm) and constant 

 throughout the study. The size range of maturing 

 males was narrow (150-220 mm). Their length dis- 

 tribution was unimodal, the modes shifting slightly 

 from 170-180 mm in June^Iuly to 190-200 mm in 

 September-October. 



The percentage of mature males steadily increased 

 from June (35%) to September (60%). In October, al- 

 most all males were mature (92%). The size range of 

 mature males was wide in June— July ( 160-290 mm ) 

 and narrowed slightly in October (170-260 mm). 



Their length composition was unimodal (200-210 

 mm) throughout the study. Spent males appeared in 

 August and represented about 4% of all males in 

 September. 



Immature females predominated in June-July 

 (70-75%), then decreased abruptly in August (10%) 

 and remained at this level until October. Size of the 

 largest immature females diminished from 280 mm 

 in June to 250 mm in October. Length composition 

 was distinctly unimodal, the modes increasing from 

 June (180-190 mm) to October (220-230 mm). The 

 percentage of maturing females expanded from June 

 (12%) to September (38%), but in October this group 

 almost disappeared. Mantle length of maturing fe- 

 males ranged from 160 mm to 330 mm. Their length 

 composition was unimodal (250-260 mm). 



Numbers of mature females decreased from June 

 (23%) to July (8%), later increased gradually until 

 October (83%). Mantle-length range for mature fe- 

 males was wide in June (200-370 mm) and slightly 

 narrower in October (200-320 mm). Length distri- 

 bution was roughly unimodal at 260-270 mm. The 

 proportion of mature females that had mated was 

 high in summer (70-80%), then decreased abruptly 

 in September (30^10%). A few spent females were 

 encountered in this region, with mantle lengths larg- 

 est in June (250-290 mm) and smallest in October 

 (200-250 mm). 



Juveniles were very abundant in June. In sum- 

 mer, they gradually decreased in numbers and al- 

 most disappeared by October. The minimum length 

 of juveniles increased from 20 mm in June— July to 

 50-60 mm in September. Their length composition 

 was unimodal; modal lengths increased from June 

 (60-70 mm) to September ( 110-120 mm). 



Gladius microstructure 



The gladius of B. magister exhibits the typical 

 oegopsid plane in structure (Arkhipkin and Bizikov, 

 1991; Bizikov, 1991 ) and is composed of three layers: 

 the middle layer, forming the rigid chitinous frame 

 of the gladius; the inner layer, filling the conus in- 

 side and forming a thick cartilaginous layer on the 

 ventral surface in the posterior part of the gladius; 

 and the outer layer, which is reduced to a film-like 

 pellicle covering the conus. 



Microstructure of the inner layer A cross section 

 of the anterior part of the conus has the shape of a 

 broad isosceles triangle, the inner layer filling the 

 entire space between the dorsal and lateral walls of 

 the conus (Fig. 6A). Regular laminae were observed 

 on sections within the inner layer. In contrast to sta- 

 toliths, no distinct growth zones were visible on the 



