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Fishery Bulletin 103(2) 



62 



Longitude °W 



Figure 1 



Distribution and density (s A ) of Argentine hake iMerluccius hubbsi) estimated from acoustic 

 surveys carried out during December (1988, 1993, 1996, and 2000) in the Isla Escondida area. 

 The size of the symbols is proportional to the percentage of spawning females (with hydrated 

 oocytes). Vertical shaded scale represents scattering coefficient values (sA), where 7.14 s A 

 units = 1 t/nautical mile 2 . 



of the main spawning ground of hake. Thus, to ana- 

 lyze spawning individuals we used only data from 33 

 fish stations located offshore within the spawning area 

 between 43°30' and 46°S (Fig. 2). Trawl station sites 

 were the same during all cruises. In January of 1996 

 and 2001 additional information from catches obtained 

 inshore near Isla Escondida was analyzed (Fig. 2). 



Argentine hake were collected with a bottom net with 

 a mouth width of about 20 m, a height of about 4 m, 

 and with 20-mm mesh at the inner cover of the codend. 

 Total length (TL) in cm, total weight (TW) in g, and 

 sex were recorded for each fish sampled; for females a 

 subsample was randomly selected from different trawl 

 stations (Table 1) and the maturity stage was deter- 

 mined for each individual. A macroscopic maturity key 

 of five stages designed for biological studies was em- 

 ployed: 1) immature; 2) developing and partially spent; 

 3) spawning (gravid and running); 4) spent; and 5) 

 resting (Macchi and Pajaro, 2003). This scale was vali- 

 dated by the histological analysis of ovaries collected 



during December 2000 and January 2001 (Macchi et al., 

 2004). Females were classified as reproductively active 

 or inactive, according to the presence of yolked oocytes 

 and atresia stages following the criteria of Hunter et al. 

 (1992). When we consider the codes used in the visual 

 assessment of maturity, stages 2 and 3 corresponded 

 to active females, which were capable of spawning at 

 the time of capture or in the near future (Hunter et 

 al., 1992). 



Abundance of active females was estimated from data 

 collected during each survey. Information obtained from 

 sampling the trawl catch was expanded to obtain esti- 

 mates of the number of individuals per length class, fol- 

 lowing the method described by Macchi et al. (2004). 



During December, information from acoustic surveys 

 was used to assign a different weight to each trawl 

 station, based on the relative density and size of the 

 school targeted by the trawl. The transect segment 

 that contained a given trawl was determined and the 

 average value of the water column scattering coefficient 



