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Fishery Bulletin 103(1) 



The modal number of myomeres (36-38; n = 47) in P. 

 semifasciata larvae matched the number of vertebrae 

 reported for adults (36-37; ?? = 50) by Gonzalez (1998). 

 The dorsal and anal fin elements reached their full 

 complement by 9-10 mm BL, whereas the caudal-, pel- 

 vic-, and pectoral-fin elements were still incomplete in 

 the size range analyzed in this study (3.3 to 11.7 mm 

 BL). Pseudopereis semifasciata and P. brasilianus post- 

 transition juveniles differ in their head shape, pigmen- 

 tation pattern, and in the number of spines of the dorsal 

 fin. The snout is larger in the Brazilian sandperch and 

 the dorsal profile of the head is less convexly shaped 

 than in P. semifasciata. These head shape differences 

 increased with size. In P. brasilianus, the lateral stripes 

 were less conspicuous than in P. semifasciata, and the 

 vertical bars appeared earlier in the development (seven 

 vertical bars were present in ca. 50 mm BL individu- 

 als). Furthermore, vertical bars in P. semifasciata were 

 more defined at the base of the dorsal fin, whereas they 

 extended below the midline in P. brasilianus. Pseu- 

 dopereis semifasciata had five dorsal-fin spines, and P. 

 brasilianus had seven spines, both in the range reported 

 by Herrera and Cousseau (1996). 



Both the epibenthic sampler and the "Piloto" trawl 

 used to collect juveniles sample the fauna from the bot- 

 tom to approximately one meter above the bottom. The 



fact that juveniles were caught in the lowest strata of 

 the water column indicates that juveniles had settled to 

 benthic habitat, even though the P. semifasciata post- 

 transition juveniles still conserved some larval pigmen- 

 tation, had not completely developed adult pigmentation 

 pattern, and had already acquired morphological pro- 

 portions similar to adults. 



Even though the abundance and distribution data 

 used in our study came from cruises that targeted other 

 species, they provide satisfactory spatiotemporal cover- 

 age. This was particularly true for the ichthyoplancton 

 surveys, which covered a great portion of the distribu- 

 tional area of P. semifasciata in the northern Patago- 

 nian shelf, mainly during the peak of the reproductive 

 season (November-December). Among the Piloto posi- 

 tive stations (« = 20), P. brasilianus was found by itself 

 only at three stations. Also, P. brasilianus was far less 

 abundant than P. semifasciata posttransition juveniles 

 in the trawl samples. As a consequence, we consider 

 that the abundance and distribution patterns of post- 

 transition pinguipedid juveniles adequately reflect the 

 abundance and distribution of P. semifasciata posttran- 

 sition juveniles in the Argentine shelf. 



The abundance and distribution of P. semifasciata 

 larvae and posttransition juveniles indicate the pres- 

 ence of at least three main reproductive grounds, one 



