Larval growth of two species of lanternfish at nearshore waters from an upwelling zone based on otolith microstructure analyses By M. F. Landaeta 1 , J. E. Contreras 1 , C. A. Bustos 1,2 and G. Mu~ noz 3 1 Laboratorio de Ictioplancton (LABITI), Facultad de Ciencias del Mar y de Recursos Naturales, Universidad de Valparaı´so, Vi ~ na del Mar, Chile; 2 Programa Doctorado en Acuicultura, Universidad Cat  olica del Norte campus Guayaca ´n, Coquimbo, Chile; 3 Laboratorio de Parasitolog ıa Marina, Facultad de Ciencias del Mar y de Recursos Naturales, Universidad de Valparaı´so, Vin ˜a del Mar, Chile Summary Larval growth and hatching days of lanternfishes Diogenich- thys laternatus and Myctophum nitidulum (Myctophidae) col- lected in September 2012 in nearshore waters (<1 km offshore) at Mejillones Bay, northern Chile, were estimated on the basis of microstructure analyses of sagitta otoliths, to establish potential differences in early traits of both species from the productive coastal waters of the Humboldt Ecosystem. Growth increments were well defined, and no accessory pri- mordia were observed in the analyses of the largest individuals in either species (8.61 and 9.17 mm BL, respectively). Both lar- val species displayed slow and similar growth rates: 0.057 Æ 0.016 mm day À1 for D. laternatus, and 0.061 Æ 0.005 mm day À1 for M. nitidulum. A large variability in the size-at- age in larvae of both species was detected. However, a recent otolith growth index showed all M. nitidulum in similar condi- tion 5 days before capture, but with three D. laternatus in bet- ter condition and only one in a poorer condition than the other D. laternatus individuals. Growth trajectories estimated by the microincrement width of sagitta otoliths, indicated the presence of fast- and slow-growing larvae for both species. Also, the back-calculated ‘birth’ days suggest a large hatching pulse for D. laternatus near the third-quarter moon. The small sampling size of M. nitidulum precluded a robust conclusion on hatching patterns, although most individuals were hatched between the third quarter and the new moon. It is suggested that the slow growth rates estimated for both larval species might be caused by cold waters from upwelling events and/or allometric growth during early development of these lanternfish. Introduction Myctophid larvae are the most abundant and speciose group and an important part of oceanic larval fish assemblages (Sassa et al., 2002; Olivar et al., 2012). The morphology of myctophid larvae is quite diverse, with almost all typical body forms of teleost fishes represented among the larval myctophids. This diversity is related to the high variety of feeding habits among the myctophid larvae, allowing the co-existence of many different species (Conley and Hopkins, 2004; Sassa and Kawaguchi, 2005). However, few studies deal with larval growth strategies among myctophids (Lin- kowski, 1991, 1996; Linkowski et al., 1993; Conley and Gartner, 2009; Bystydzie nska et al., 2010). In the Humboldt Current, the most abundant and recur- rent larval species are Diogenichthys laternatus and D. atlan- ticus (Evseenko, 2006; Acu~ na and Cabrera, 2007). Larval D. laternatus occurs in shallower waters (0–20 m layer) dur- ing non-upwelling conditions, whereas in upwelling condi- tions the larvae are found below 20 m depth (Rojas et al., 2002). These larvae are opportunistic diel feeders and predate upon invertebrate eggs, nauplii, ostracods, copepods, copepo- dites, larval mollusks and polychaetes, juvenile Nemertea and tintinnids (Rodriguez-Gra~ na et al., 2005). Another important species in the Humboldt Current is Myctophum nitidulum, the second most important fish prey in the diet of the jumbo squid (Rosas-Luis et al., 2011). The larval period including metamorphosis is approximately 65 days, and the relationship between fish growth and oto- liths changes as a function of the lunar phases (Giragosov and Ovcharov, 1992). In the Kuroshio Current, larval M. nitidulum occurs mainly in the 75–100 m layer (Sassa et al., 2002), and appears frequently off northern Chile but at low abundance during the austral spring season (Loeb and Rojas, 1988; Rojas et al., 2002). The microstructure of larval Diogenichthys laternatus otoliths has not been examined previously. The daily char- acter of growth increments in lanternfish otoliths (sagittae) has been observed and verified in tropical, subtropical and tropical-temperate myctophids during juvenile and adult stages (Gartner, 1991a,b; Suthers, 1996; Hayashi et al., 2001; Moku et al., 2001), as well as larval stages (Moku et al., 2005). A lunar periodicity in the deposition of the increments in Myctophum asperum has also been described (Hayashi et al., 2001). The ‘larval zone’ of the myctophid otoliths is formed during the presence of larvae in highly dynamic epipelagic layers (Greely et al., 1999) where they perform restricted diel vertical migrations (Sassa et al., 2007). The goal of this research was to compare the early life his- tories of these two myctophid fish found in the coastal waters of an upwelling zone, on the basis of the sagittal otolith microstructure of the larvae. J. Appl. Ichthyol. (2014), 1–8 © 2014 Blackwell Verlag GmbH ISSN 0175–8659 Received: April 27, 2014 Accepted: June 5, 2014 doi: 10.1111/jai.12639 Applied Ichthyology Journal of