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Fishery Bulletin 103(2) 



batch-fecundity-size relationship, and spawning fre- 

 quency. The batch fecundity-total-length relationship 

 and the spawning frequency values used for December 

 (1988-2000) and for January (1996-2001) were those 

 estimated in December 2000 and January 2001, re- 

 spectively (Macchi et al., 2004). We assumed that these 

 values were applicable to all previous years, because in 

 general, annual differences of these variables were not 

 significant for hake females of the same length range 

 (Macchi et al., 2004). 



Egg production by length for each month was esti- 

 mated by multiplying the number of active females in 

 each length class by the batch fecundity corresponding 

 to that length class and by the number of spawnings es- 

 timated for each month. The sum of the egg production 

 values estimated across the size range was the total 

 number of eggs produced in the sampled area during 

 each month (December or January) in different years. 



To analyze the relationship between egg production 

 and recruitment, estimates of the relative abundance at 

 age 1 (number of individuals per trawl hour) of Argen- 

 tine hake were used as a recruitment index. These data 

 were obtained from samples to assess hake juveniles 

 collected from the whole area covered during the cruises 

 carried out in January 1997-2001. In 2002, this index 

 was estimated with samples collected in the same area, 

 but in a different month (March) (GEM, unpubl. data 2 ). 

 The number of age-1 individuals in year t+1 was the 

 recruitment index corresponding to the year t. 



Results 



(with hydrated oocytes) in the Isla Escondida area during 

 December 1988, 1993, 1996, and 2000. A decline in hake 

 abundance from 1988 to 2000 was observed — in particu- 

 lar, a drastic decrease in 2000, when the mean density 

 value (14.6 t/nautical mile 2 ) was thirty times less than 

 that estimated in 1988 (469.2 t/nautical mile 2 ). During 

 December 1988-96, spawning females were mainly 

 located in the northern area (between 43° and 44°S) 

 inshore at depths lower than 50 m. In 2000 reproduc- 

 tive activity was concentrated at the same latitude as 

 in previous years, but offshore (Fig. 1). 



In January 1996 the highest densities of M. hubbsi 

 and the spawning females of this species were located 

 in the Isla Escondida area (Fig. 2). Between 1997 and 

 2000 we did not obtain data from this zone, but the 

 increase in the proportion of spawning hake in deep 

 waters observed since 1998 indicates a spatial change 

 in the reproductive area. During January 2000 and 

 2001, in addition to the increase of reproductive females 

 offshore, the abundance of hake was higher than that 

 estimated previously for the same area (Fig. 2). In Jan- 

 uary 2001, trawl stations located near Isla Escondida 

 showed very low values of hake density, in contrast to 

 that observed offshore. This contrast could be attributed 

 to the movement of individuals from the traditional 

 spawning area near the coast to deeper water. 



Egg production 



Egg production estimated for December in the Isla 

 Escondida area showed a considerable decrease from 

 1988 to 2000 (Fig. 3). The number of eggs produced 



Abundance of hake and location of spawning females 



Figure 1 shows the acoustic densities estimated for 

 Argentine hake and the distribution of spawning females 



- GEM (Grupo de Evaluacibn Merluza). 2002. Evaluacion 

 del estado del recurso merluza (Merluccius hubbsi) al sur de 

 41° S, ano 2002. Unpubl report. INIDEP, CC. 175, Mar 

 del Plata (7600), Argentina. 



