696 



Fishery Bulletin 101(3) 



The highest larval concentrations (>100 larvae/1000 m'') 

 occurred at the southeastern tip of the island and averaged 

 27 ±46 larvae/1000 m'' (Fig. 1). No significant differences 

 were found between day and night larval concentrations 

 (Kruskal-Wallis test=0.047; P>0.05). Around Salas and 

 Gomez Island, larvae were caught only at two stations 

 6 nmi west and south of the island, and in mean concentra- 

 tions <10 larvae lOOO/m-^ (Fig. 2). No larvae were caught in 

 any of the eight stations sampled between the two islands. 

 Body lengths of larvae caught in both islands ranged from 

 8 to 16 mm SL, and over 30% of the larvae were around 12 

 mm SL (Fig. 4). 



Discussion 



Postflexion larvae of D. dimorphicum are likely to be 

 confused with those of four other co-occurring percophid 

 species (see Table 1), and those of the creediid Crystallo- 

 dytes pauciradiatus that occur in the same region (Castro 

 and Landaeta, 2002) and have similar bodies with little or 

 no pigment. In the case of the percophids, the digitiform 

 opercular processes exclusive to D. dimorphicum , together 

 with dorsal and anal-fin meristics, should be sufficient 

 to distinguish between postflexion larvae of all species. 

 Larval C. pauciradiatus can be identified by using myo- 

 mere counts (56-58 vs. 31-35 in D. dimorphicum ) and their 

 small, early forming posterior preopercular spines (Reader 

 et al., 2000). 



Our collection of D. dimorphicum larvae at Easter Island, 

 some 453 km to the southwest of Salas y Gomez Island 

 where it was first described (Parin, 1990), constitutes the 

 first record for Easter Island, thereby extending the known 

 range of this species over the South Pacific plate. Despite 

 numerous past fish surveys around Easter Island (i.e. Ran- 

 dall and Cea-Egaiia, 1984; Mujica, 1993), adults of this dwarf 

 percophid had not been reported there, a fact that could be 

 attributed to factors such as collection methods, depth of 

 surveys, and the very small size of these larvae. However, the 

 presence and abundance of larval D. dimorphicum reported 

 in this study, and the fact that they were among the five most 

 abundant larval taxa caught around Easter Island (Castro 

 and Landaeta, 2002), implies the existence of a well-estab- 

 lished breeding population. Biogeographically, this finding 

 also suggests that larval drift could play an important role in 

 the expansion of this and other fish species that have pelagic 

 larvae in this region of the southeast Pacific. In this context, 

 it is perhaps relevant that expansions offish ranges are not 

 uncommon in this region, even though both Easter and Sa- 

 las y Gomez Islands lie in different biogeographic provinces 

 (Parin et al., 1997). A good example is the pentacerotid Pen- 

 taceros decacanthus, which was regarded as endemic of the 

 Nazca and Salas y Gomez Ridges until it was recorded in 

 Easter Island (Parin and Kotlyar, 1988). 



Acknowledgments 



We would like to thank Paula Rosenborg and all the crew 

 from the AGOR Vi.dal Gormaz for their help with sampling. 



We also thank Muneo Okiyama for his comments on iden- 

 tification of percophid larvae. This research was funded 

 by the Comite Oceanografico Nacional (CONA), Chile, and 

 forms part of a study on distribution patterns and larval 

 accumulation around oceanic islands headed by Leonardo 

 Castro. 



Literature cited 



Belyanina, T. P. 



1989. Ichthyoplankton in the regions of the Nazca and Salas 

 y Gomez submarine ridges. J. Ichthyol. 29(5):84— 90. 



1990. Larvae and fingerlings of little-known benthic and 

 benthopelagic fishes from the Nazca and Salas y Gomez 

 ridges. J. Ichthyol. 30(6):1-11. 



Castro. L. R., and M. F. Landaeta. 



2002. Patrones de distribucion y acumulacibn larval en tomo 

 a islas oceanicas: Isla de Pascua y Salas y Gomez. Cienc. 

 Tecnol. Mar. CONA 25(1):131-145. 

 Mujica, A. 



1993. Zooplancton de las aguas circundantes a la Isla de 

 Pascua (27°08'S-109°26W). Cienc. Tecnol, Mar. CONA 

 16:55-61. 

 Neira, F. J., A. G. Miskiewicz, and T. Tmski. 



1998. Larvae of temperate Australian fishes. Laboratory 

 guide for larval fish identification, 474 p. Univ. Western 

 Australia Press, Nedlands, Australia. 

 Okiyama, M. 



2000. Percophidae (sandfishes, duckbills). //; The larvae of 

 Indo-Pacific coastal fishes: an identification guide to marine 

 fish larvae (J. M. Leis and B. M. Carson-Ewart, eds.), p. 

 554-560. Brill, Leiden, The Netheriands. 

 Parin, N. V. 



1985. A new hemerocoetine fish, Osopsaron karlik ( Percophi- 

 dae, Trachinoidei) from the Nazca submarine ridge. Jpn. 

 J. Ichthyol. 3 1(4 1:358-361. 

 1990. Percophid fishes (Percophidae) from the Salasy Gomez 

 ridge (Southeast Pacific). J. Ichthyol. 30(l):68-79. 

 Parin, N. V., and A. N. Kotlyar 



1988. A new boarfish, Pentaceros quinquespinis (Pentacero- 

 tidae), from the Southeast Pacific. Vopr Ikhtyol. 28(3): 

 355-360. 

 Parin, N. V., A. N. Mironov, and K. N. Nesis. 



1997. Biology of the Nazca and Sala y Gomez submarine 

 ridges, an outpost of the Indo-West Pacific fauna in the 

 Eastern Pacific Ocean: composition and distribution of the 

 fauna, its communities and history. Adv. Mar Biol. 32: 

 147-242. 



PotthofT, T 



1984. Clearing and staining techniques. In Ontogeny and 

 systematics of fishes (H. G. Moser, W. J. Richards. D. M. 

 Cohen, M. P. Fahay A. W. Kendall, and S. L. Richardson, 

 eds.). p. 35-37. Am. Soc. Ichthyol. Herpetol. Special Pub- 

 lication 1. 



Randall, J. E., and A. Cea-Egana. 



1984. Native names of Easter Island fi.shes, with comments 

 on the origin of the Rapanui people. Occas. Pap. Bernice 

 P Bi.shop Mus. 25(12):1-16. 



Reader, S. E., and F J. Neira. 



1998. Percophidae: sandfishes, duckbills. In Larvae of 

 temperate Australian fishes. Laboratory guide for larval 

 fish identification IF J. Neira, A. G. Miskiewicz, and T. 

 Tmski. eds.). p. 358-361. Univ. Western Australia Press; 

 Nedlands, Australia. 



