10 



Fishery Bulletin 98(1) 



Females 



Mar. Ill 



100 160 2O0 2»0 300 9ftO 400 



Apr. I 



100 «0 200 2aO 300 380 400 



Apr. II 



100 ISO 200 2SO 9O0 360 400 



Apr.  



no ISO 200 250 300 350 



Mantle length (mm) 



Males 



Age structure 



Mar, 



Mar. M 



^ • 74 I4at 



lOO MO 200 260 300 360 400 



A M J J A 8 O 



10 

 IS 



Apr, 



160 200 aso aoo 3»o 



Apr. II 



100 160 200 250 300 S«0 400 



Apr, II 



A 8 O 



Apr. M 



ISO 200 250 300 360 4O0 



Mantle length (mm) 



Hatching month 



Figure 8 



Length-frequency and hatching month compositions (age structures) of Illex argentmus of the fishery' region of 51-52°S within the 

 EEZA in March-April 1991. Symbols are the same as in Figure 4. 



(Arkhipkin, 1990; Rodhouse and Hatfield, 1990). 

 Taking into account the rather stable hatching month 

 compositions during February-April, the squid were 

 not performing any active spatial migrations after 

 their arrival into the region of 45-49°S. Therefore, 

 growth curves that were constructed on the basis of 

 the increase in modal lengths of squid during Feb- 

 ruary-April are valid, and growth rates calculated 

 from these curves are probably close to actual growth 

 rates (Koronkiewicz, 1986; Hatanaka, 1988). During 

 feeding, some redistribution of the /. argentmus pop- 



ulation was observed; large maturing and mature 

 squid (mainly females) tended to shift from the shelf 

 ( 130-150 m depth) in a northeast direction and to con- 

 centrate over the shelf edge (160-170 m depth). This 

 shift resulted in an increase in their proportion in 

 catches in the region outside the EEZA (45-47°S) and 

 a simultaneous decrease in their proportion within 

 the EEZA (47^9°S). A similar shift of maturing squid 

 from the shelf to the shelf edge has been noted by 

 Brunetti et al. ( 1998). Probably, this shift of maturing 

 and mature females was also a reason for the consid- 



