28 



Fishery Bulletin 94(1), 1996 



ters (Fedorets and Kozlova, 1988; Shevtsov, 1990). 

 However, because B. magister adults occur mainly 

 at and over the slope, the first route seems more 

 likely. Taking into account the similarity of body 

 shape of B. magister and /. argentinus, as well as 

 the depths and water temperatures of their spawn- 

 ing migrations, we assume that migratory swimming 

 rates of B. magister may resemble those of/, argen- 

 tinus: 0.46 of absolute length (including mantle 

 length, length of head and arms, AL) per sec 

 (Arkhipkin, 1993). As the modal AL values in B. 

 magister are 350-390 mm for mature males and 440- 

 490 mm for mature females (our data), their aver- 

 age migratory rates may be estimated as 0.1-0.18 

 msec" 1 and 0.20-0.23 msec -1 , respectively. At this 

 speed B. magister females may reach spawning 

 grounds near the Commander Islands in 66-73 days 

 and males in 80-92 days. But, in fact, B. magister 

 cannot migrate at this speed, because its mantle is 

 more watery and less muscular than that of om- 

 mastrephids: the protein content of B. magister 

 mantle muscles is 13.5% compared with 20% which 

 is typical for ommastrephids (Shevtsov and Dolbnina, 

 1975). Nevertheless, the data of Fedorets (1986a), 

 who found dense aggregations of B. magister near 

 the Commander Islands in November-January, sup- 

 port our suggestion of a squid migration to the Com- 

 mander Islands. During this period, aggregations of 

 B. magister near the Commander Islands consisted 

 entirely of mature males and females of quite con- 

 stant sizes (210-220 mm and 270-280 mm ML, re- 

 spectively). However, these aggregations were ob- 

 served at depths of 150-250 m, whereas B. magister 

 migrates to much greater depths to spawn (1,000- 

 1,100 m [Okiyama, 1993]). Thus, it is possible that 

 mature squid of the fall-hatched group spawned one- 

 two months later (in January-March) at mean ages 

 around 18 months. It is hardly possible thatB. mag- 

 ister from the western Bering Sea should reach even 

 the Near Islands, the westernmost of the Aleutian 

 Islands, because the northward current in the deep and 

 wide Near Strait is very strong and may cross the squid 

 migratory route. Kovalev ( 1990) has shown by the sub- 

 strate-specific properties of cholinesterases that squid 

 from the Pribilov-Alaska region (eastern Bering Sea) 

 are different from those of the Navarin-Olyutorsky 

 region, suggesting some degree of genetic isolation. 



To estimate the total longevity of cold-water squid, it 

 is important to consider the duration of their embry- 

 onic phase. Recently, Laptikhovsky ( 1991 ) modeled lon- 

 gevity of the embryonic phase in squid by using two 

 independent variables: water temperature and aver- 

 age egg diameter. Taking into account the large egg 

 size of B. magister (3.5 mm [Fedorets and Kozlova, 

 19861; our data) and the extremely cold water over its 



spawning grounds ( 1.5-2. 5°C [Fedorets, 1986a]), we 

 believe the duration of the embryonic phase for B. 

 magister could be from 4 to 6 months. This estimation 

 corresponds well with data of von Boletzky ( 1994 ), who 

 considered the duration of embryonic development in 

 decapods as ranging from 6 to 12 months at water tem- 

 perature 2-5°C. Thus, the life cycle of the fall-hatched 

 group of B. magister could last about two years (6 

 months of embryonic phase and 18 months of postem- 

 bryonic development). The life cycles of other seasonal 

 groups require further investigations. 



Acknowledgments 



We gratefully acknowledge the generous help of the 

 officers and crew of the Japanese trawlers Tenyu- 

 Maru N 57, Kaiyo-Maru N 28, and Kashima-Maru 

 N 8. We would like to thank A. N. Golub and Zh. N. 

 Scherbich who kindly helped in statolith processing 

 and reading in the Laboratory of Commercial Inver- 

 tebrates of AtlantNIRO. We extend thanks to A. V. 

 Pavlov for his assistance in data processing. We 

 thank three anonymous referees for their criticisms, 

 comments, and for improving the English of the 

 manuscript. This research was funded by the Rus- 

 sian Federal Committee of Fisheries. 



Literature cited 



Alexeev, D. O., and V. A. Bizikov. 



1986. Some biological and ecological features of schoolmas- 

 ter gonate squid Berryteuthis magister (Gonatidae) off 

 Symushir Island. In Resources and fishery perspectives 

 of squid of the World ocean, p. 50-57. VNIRO Press, Mos- 

 cow, Russia. (In Russian with English abstract.] 

 Alexeev, D. O., V. A. Bizikov, D. N. Khromov, and 

 A. A. Pomozov. 



1989. Underwater observations on the behavior and dis- 

 tribution of a gonate squid Berryteuthis magister and other 

 cephalopods in the northwestern Pacific ocean. In Un- 

 derwater explorations for fisheries and biooceanological stud- 

 ies, p. 66-77. VNIRO Press, Moscow, Russia. [In Russian.] 



Arkhipkin, A. I. 



1990. Edad y crecimiento del calamar Illex argentinus. 

 Frente Maritimo 6A:25-35. 



1993. Age, growth, stock structure and migratory rate of pre- 

 spawning short-finned squid lllex argentinus based on sta- 

 tolith ageing investigations. Fish. Res. (Amst. ) 16:313-338. 

 Arkhipkin, A. I., and S. A. Murzov. 



1985. Methods of statolith processing for age and growth 

 studies in squid. Zool. Zh. 64(11 ):1721-1726. [In Russian 

 with English abstract.] 

 Arkhipkin, A. I., and V. A. Bizikov. 



1991. Comparative analysis of age growth estimates using 

 statolith and gladius in squid. In P. Jereb, S. Ragonese, 

 and S. von Boletzky (eds.i, Squid age determination using 

 statoliths, p. 19-33. N.T.R. -Institute di Tecnologia della 

 Pesca e del Pescato Spec. Publ. 1, Mazara del Vallo, Italy 



