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Experimental assessment of the effects of a Neotropical nocturnal piscivore on juvenile native and invasive fishes Santos, Alejandra F. G. N. Alcaraz, Carles Santos, Luciano N. Hayashi, Carmino García-Berthou, Emili Producció Animal Aigües Marines i Continentals 574 We experimentally examined the predator-prey relationships between juvenile spotted sorubim Pseudoplastystoma corruscans and young-of-the-year invasive and native fish species of the Paraná River basin, Brazil. Three invasive (peacock bass Cichla piquiti, Nile tilapia Oreochromis niloticus, and channel catfish Ictalurus punctatus) and two native (yellowtail tetra Astyanax altiparanae and streaked prochilod Prochilodus lineatus) fish species were offered as prey to P. corruscans in 300 L aquaria with three habitat complexity treatments (0%, 50% and 100% structure-covered). Prey survival was variable through time and among species (C. piquiti < O. niloticus < A. altiparanae < P. lineatus < I. punctatus), depending largely on species-specific prey behavior but also on prey size and morphological defenses. Habitat complexity did not directly affect P. corruscans piscivory but some prey species changed their microhabitat use and shoaling behavior among habitat treatments in predator’s presence. Pseudoplatystoma corruscans preyed preferentially on smaller individuals of those invasive species with weak morphological defensive features that persisted in a non-shoaling behavior. Overall, our results contrast with those in a companion experiment using a diurnal predator, suggesting that nocturnal piscivores preferentially prey on different (rather diurnal) fish species and are less affected by habitat complexity. Our findings suggest that recovering the native populations of P. corruscans might help controling some fish species introduced to the Paraná River basin, particularly C. piquiti and O. niloticus, whose parental care is expected to be weak or null at night. This work was funded by CNPq, Conselho Nacional de Desenvolvimento Científico e Tecnológico, Brazil (graduate grant to A. F. G. N. Santos, process nº 142572/2004-7 and process nº 210199/2006-7; Edital Universal, process nº 478541/2004-0), Programme Alßan of the European Union (Programme of High Level Scholarships for Latin America, grant to L. N. Santos), the Spanish Ministry of Science (projects CGL2006-11652-C02- 01/BOS and CGL2009-12877-C02-01), and the Government of Catalonia (Catalan Government Distinction Award for University Research to E. García-Berthou). We especially thank Drs. A.A. Agostinho, A. Bialetzki, and H.F. Júlio Jr, from Núcleo de Pesquisa em Limnologia, Ictiologia e Aquicultura (Nupelia, UEM, Brazil), for providing the infrastructure for the laboratory experiments. This study is part of the first author’s Ph.D thesis. info:eu-repo/semantics/publishedVersion 2012-03-30 info:eu-repo/semantics/article Santos, Alejandra F.G.N., Carles Alcaraz, Luciano Neves Dos Santos, Carmino Hayashi, and Emili García‐Berthou. 2012. “Experimental Assessment of the Effects of a Neotropical Nocturnal Piscivore on Juvenile Native and Invasive Fishes.” Neotropical Ichthyology. 10 (1): 167–76. doi:10.1590/s1679-62252012000100016. 1679-6225 http://hdl.handle.net/20.500.12327/2480 https://doi.org/10.1590/S1679-62252012000100016 eng Neotropical Ichthyology MEC/ /CGL2006-11652-C02-01/ES/EXITO INVASOR DE LA GAMBUSIA (GAMBUSIA HOLBROOKI): PLASTICIDAD ECOLOGICA/BOS MICINN/Programa Nacional de Proyectos de Investigación Fundamental/ CGL2009-12877-C02-01/ES/ / Attribution-NonCommercial 4.0 International http://creativecommons.org/licenses/by-nc/4.0/ info:eu-repo/semantics/openAccess 10 Sociedade Brasileira de Ictiologia