200 



Fishery Bulletin 103(1) 



Individuals became more thick bodied as they devel- 

 oped. The body was elongate and relative body depth 

 remained fairly constant throughout development. The 

 snout was longer and rounded, and relative head length 

 was moderate. The mouth was terminal, reaching to 

 the middle of the eye, and had fleshy lips. Both jaws 

 presented only caniniform teeth. Two opercular spines 

 were also present in all specimens studied. Relative 

 head depth decreased slightly during development, but 

 not relative eye diameter. Gut length was moderate 

 (PAL/BL 0.38-0.48), and the anus was situated near 

 the midpoint of the body (Fig. 3D). Relative predorsal 

 length (0.26-0.30) diminished during development. 



The scales were ctenoid. Smaller posttransition juve- 

 niles (BL s33 mm) retained some of the larval pigmen- 

 tation pattern. Larger juveniles showed several dark 

 vertical bars, not completely defined at this stage of de- 

 velopment, and three horizontal stripes along the body 

 (Fig. 3D). Vertical bars developed progressively from the 

 caudal peduncle to the head. Two lateral stripes formed 

 continuous bands along each side of the body, almost 

 entirely above the midline. The upper stripe developed 

 from the tip of the snout and the lower one began below 

 the eye, both extending to the anterior caudal peduncle. 

 Another stripe developed from the dorsal region of the 

 head between the eyes and extended along the dorsal 

 fin, joining the upper lateral stripe at the posterior 

 third part of the body. In large posttransition juveniles 

 (a47 mm BL), the membrane of the dorsal fin was pig- 

 mented more densely between the spines than between 

 the rays; there were also dark blotches on the mem- 

 brane between the rays. Anal-fin membranes were more 

 pigmented than those of the dorsal fin. The membranes 

 of the pectoral, pelvic, and caudal fins, and the external 

 border of the membranes of the dorsal fin, were yellow 

 in frozen individuals. By 22 mm BL, the conspicuous 



50 -i 



~ 40 



30  



20 



10  



t 



r 



BD/TLx100 HL/TLx100 PAL/TLx100 PDL/TLx100 

 Body proportions 



Figure 4 



Comparisons between body proportions in posttransition 

 juveniles (white bars) and adults (gray bars) of Pseudopercis 

 semifasciata. Relative measures were taken with respect 

 to total length (TL). Body depth (BD), head length (HLi, 

 preanal length (PAL), predorsal length (PDL). Proportions 

 for adults were estimated from 99 individuals between <30 

 cm and 90 cm TL (Gonzalez, 1998). 



dark blotch observed in adult P. semifasciata on the 

 base of the caudal fin upper lobe (Herrera and Cous- 

 seau, 1996) was already present (Fig. 3D). The pelvic 

 fin was large and slightly shorter than the pectoral fin, 

 whose margin was rounded. 



Abundance and distribution 



Larvae Larvae of Argentine sandperch occurred between 

 36°42'S and 46°30'S, mainly in coastal waters, in the 

 vicinity of the 50-m isobath (Fig. 5). The southernmost 

 limit where larvae were collected was within San Jorge 

 Gulf, which was surveyed in late March (fall). Larvae 

 were present in only 3.55% of the stations in densities 

 that varied between two and 74 larvae/10 m 2 of sea 

 surface (Table 4). Greater densities (>20 larvae/10 m 2 

 of sea surface) were obtained in December 1986, 1996, 

 and 1999, off the coast between Engano Bay and Isla 

 Escondida. Positive stations formed scattered clumps 

 along the whole distributional area of the species. Min- 

 imum and maximum depths sampled were 20 and 71 m, 

 respectively. Water temperature at 10 m depth at posi- 

 tive stations varied between 12.3°C (March 1985) and 

 18.7°C (December 1999) (mean temperature [±SE]: 

 15.2°C [±2.1°C]). 



Posttransition juveniles Posttransition pinguipedid 

 juveniles were found between 42°27'S and 43°37'S in 

 February and March, and between 43°17'S and 44°58'S 

 from April to June, primarily in the vicinity of the 50-m 

 isobath (Fig. 6, A and B). The percentages of positive 

 stations were 5.9% and 7.7% in summer and fall surveys, 

 respectively. Maximum juvenile densities were 4410 

 individuals/nmi- in summer and 27,027 individuals/nmi 2 

 in fall (Table 5). 



The grid of stations used during the summer and 

 fall cruises overlapped (Fig. 6, A and B), cover- 

 ing the main area of concentration of P. semifas- 

 ciata (Otero et al., 1982). Minimum and maximum 

 depths were 54 and 74 m in summer surveys (mean 

 depth [±SE]: 64.5 [±10.0] m), and 34 and 79 m in 

 fall surveys (mean depth [±SEJ: 60.4 [+13.7] m). 

 The distributional ellipses calculated for summer 

 and fall from the positive stations were small and 

 widely separated. Maximum summer densities of 

 posttransition pinguipedids were found southeast 

 of Peninsula Valdes, whereas greatest fall densities 

 were detected northeast of Camarones Bay (Fig. 6, 

 A and B). 



Discussion 



Literature describing the early stages of species 

 belonging to the family Pinguipedidae (formerly 

 Mugiloididae) is scarce. The few available studies 

 refer to the larval development of Parapercis spp. 

 (Leis and Rennis, 1983; Watson et al., 1984; Houde 

 et al., 1986; Neira, 1998; Leis and Rennis, 2000) 



