NOTE Macchi et al.: Effect of the spawning pattern of Merlucaus hubbsi on recruitment 



449 



1600 



2 1200 



800 



400 - 



XZL 



2000 



1600 



1200 



800 



400 



1988 



1993 



1996 



2000 



Figure 3 



Egg production of Argentine hake (Merluccius. hubbsi) 

 estimated for December (1988. 1993, 1996, and 2000) 

 in the Isla Escondida area (bars), and production by 

 unit-weight of reproductively active female (line) for 

 the same month. 



per unit of weight (kg of active females) declined from 

 1988 to 1996, and to a value of around 1700 eggs/kg in 

 the last year (Fig. 3). During December 2000, however, 

 relative egg production increased to 2000 eggs/kg, which 

 can be attributed to the effect of a higher proportion of 

 larger females in reproductive activity. In fact, when 

 the percentage of eggs produced by length class was 

 analyzed, the distribution obtained for December 2000 

 was different from that for 1988, 1993, and 1996 (Fig. 4). 

 During the earlier years, production mainly depended on 

 young females (<50 cm TL), whereas in December 2000 

 most of the eggs produced (about 70%) where spawned 

 by females larger than 50 cm TL. 



Egg production estimated for the offshore area in Jan- 

 uary increased from 1996 to 2001 (Fig. 5), in contrast to 

 that observed during December in shallow water near 

 Isla Escondida. The number of eggs produced per unit 

 of weight of active females was similar in 1996 and 

 1997 (about 1600 eggs/kg), but increased in 1998-2001 

 to about 1800 eggs/kg. This increase was similar to 

 that observed for December 2000, which was attributed 

 to the higher proportion of larger females within the 

 spawning fraction of hake. In fact, percentage-distribu- 

 tion of eggs produced by length class showed a change 

 beginning in 1998 (Fig. 6). In 1996 and 1997, 70% of 

 the eggs were produced by young females (<50 cm TL), 

 but subsequent production of old females increased to 

 60% in 1998-99 and to 70% in 2000-01. 



from the offshore area was used; thus, the number of 

 eggs estimated was a fraction of that produced by all 

 spawning females in January. However, the increase in 

 egg production observed offshore for the parental stock 

 in 2000 and 2001 was coincident with higher values of 

 age-1 recruitment estimated one year later during 2001 

 and 2002, respectively (Table 2). 



Recruitment 



Relative abundance data for hake at age 1 (year t+1) 

 in the north Patagonian area were contrasted with the 

 egg production obtained in January from the previous 

 year (t). To estimate egg production, only information 



Discussion 



The spatial pattern of M. hubbsi spawning aggrega- 

 tions inshore and offshore of the north Patagonian area 

 between 1988 and 2001 has changed since 1998. This 



