Marine Biology (2006) 149: 1519–1537 DOI 10.1007/s00227-006-0319-z RESEARCH ARTICLE Rodolfo Cornejo · Rolf Koppelmann Distribution patterns of mesopelagic fishes with special reference to Vinciguerria lucetia Garman 1899 (Phosichthyidae: Pisces) in the Humboldt Current Region off Peru Received: 29 November 2005 / Accepted: 24 March 2006 / Published online: 28 April 2006  Springer-Verlag 2006 Abstract The horizontal and vertical distributions of adult mesopelagic Wshes are described from acoustic and trawl surveys over the full-depth of 500 m at 169 sta- tions on a longitudinal transect crossing the Humboldt Current (03°45'S, 81°76'W and 18°23'S, 71°13'W) at 50–200 nautical miles oV Peru during austral spring (October–November) of 2001, 2002 and 2003. A total of 2,952 kg of Wshes was collected, which included 13 fami- lies, 23 genera and 28 species. The mesopelagic commu- nity is dominated by the families Phosichthyidae (Vinciguerria lucetia), Myctophidae (Diogenichthys lat- ernatus and Lampanyctus idostigma) and Bathylagidae (Leuroglossus urotranus), accounting for 60.4, 12.8 and 3.7%, respectively, of the total catch. Based on horizon- tal distribution patterns these species were categorized into three groups, i.e. northern-central upwelling front group (L. urotranus, Nemichthys fronto and Scopelar- choides nicholsi), Southern upwelling front group (Hygophum reinhardti, Myctophum nitidulum, Paralepis sp and Scopeloberyx sp.) and pan-Humboldt Current group (V. lucetia, D. laternatus, L. (Nannobrachium) idostigma, L. omostigma, M. aurolaternatum, Triphotu- rus oculeus, Bathylagus (Melanolagus) berycoides, Leu- roglossus stilbius, Argyropelecus aVinis, Sternoptyx obscura, Melamphaes sp., Stomias sp. and Scopelosaurus sp.). Nighttime vertical distribution was characterized by a single abundance peak in the upper 50 m. Daytime patterns showed three peaks of abundance: an upper peak, in the upper 100 m, a midwater peak between 200 and 400 m, coinciding with an oxygen minimum zone, and a deeper peak between 400 and 500 m. V. lucetia was dominant in the upper and midwater peaks while myctophids, other planctivorous and piscivorous Wshes were distributed in the midwater. Acoustic back-scat- tered energy (S a ) was ubiquitous in the region. Maxi- mum S a was mainly located between 11° and 18°S during day and night. V. lucetia is a signiWcant compo- nent of the sound-scattering layers in the Humboldt Current Region oV Peru. Introduction Mesopelagic Wshes are important components of oceanic ecosystems because of their common and abundant dis- tribution in the world oceans except for the Arctic (Ahl- strom et al. 1976; Sassa et al. 2002; McClatchie and Dunford 2003). They are main consumers of zooplankton and larval and juvenile Wshes and are important prey for the higher producers such as tunas, squids and dolphins in the oceanic food web, thus providing a link between top predators and zooplankton (Kinzer and Schulz 1985; Williams et al. 2001). The remarkable features of mesope- lagic Wshes is that dominant Wshes such as myctophids undergo extensive diel vertical migration (DVM) and form dense patches, which can be observed by acoustic means as sound-scattering layers (SSLs) (Lapko and Iva- nov 1994; Luo et al. 2000). The DVM is one of the most widespread patterns of animal behavior in the mesope- lagic zone (Frank and Widder 2002) which inXuences the life history of nonmigrating and migrating Wshes directly and indirectly (Willis and Pearcy 1982). Thus, the migrat- ing animals inXuence the feeding behavior and spatial distribution patterns of predators (Konchina 1981; Benoit-Bird and Au 2002; Bertrand et al. 2002). DVM of mesopelagic Wshes has been shown to contribute sig- niWcantly to the rapid vertical modiWcation and transport of organic matter from epipelagic to mesopelagic zones, Communicated by O. Kinne, Oldendorf/Luhe R. Cornejo (&) Departamento de OceanograWa, Universidad de Concepcion, Chile Cabina 9, Concepcion , Chile E-mail: rocornejo@udec.cl Tel.: +56-41-204239 R. Koppelmann (&) Institute of Hydrobiology and Fishery Science, University of Hamburg, Zeiseweg 9, 22765 Hamburg, Germany E-mail: koppelmann@uni-hamburg.de Tel.: +49-40-428386679