Feeding strategy of the introduced Astronotus crassipinnis (Cichlidae) in upper Paraná river floodplain

Abstract

The cichlid Astronotus crassipinnis (Heckel, 1840) known as “oscar” or “apaiari” is native to the Amazon basin and presents an omnivorous feeding habit, with a tendency to carnivory. The species was introduced in the upper Paraná River floodplain, where the trophic strategies adopted by the species are not well-known. The objective of this study was to characterize the diet of A. crassipinnis in different size classes to identify ontogenetic differences in diet composition and to determine its feeding behavior in the invaded floodplain. In addition, we experimentally compared the feeding behavior of A. crassipinnis with Hoplias sp. 2, a native piscivorous. We evaluated the predation rate of the two species with different prey (fish and shrimp). Astronotus crassipinnis consumed items from several trophic levels in the juvenile stage, characterizing an omnivore feeding. In the adult stage, A. crassipinnis displayed a specialist strategy in which fish and mollusks dominated the diet. Under controlled conditions, A. crassipinnis consumed more shrimp than Hoplias sp. 2. The preference for shrimp during the experiment contrasted to its feeding in natural environments, showing the potential trophic plasticity of A. crassipinnis. The piscivorous habit in the invaded environment can be considered a trophic strategy of A. crassipinnis, which feeds on an abundant resource in the upper Paraná River floodplain. In conclusion, the ontogenetic diet shifts and the trophic opportunism of the carnivore adults can be the strategies used by the species to invade and settle the floodplain. The piscivorous strategy of A. crassipinnis may impact fish biodiversity, altering ecosystem functioning.

Dynamic of fish trophic guilds in the plateau-plain gradient in the Paraguay River, Northern Pantanal

“…The guilds were attributed according to the most expressive behaviour reported by the specialized bibliographies (Sazima & Machado, 1983;Lolis & Andrian, 1996;Resende et al, 1996;Resende, 2000;Hahn et al, 2002;Lonardoni et al, 2006;Ibañez et al, 2007;Corrêa et al, 2009;Brandão-Gonçalves et al, 2010;Sampaio & Goulart, 2011;Prado, 2015;Resende et al, 2016;Polaz et al, 2017;Lopes et al, 2022). The invertivores' guild was composed by invertivorous, insectivorous, invertivorous/insectivorous and zooplanktophagous species.…”

A new species of Astronotus (Teleostei, Cichlidae) from the Orinoco River and Gulf of Paria basins, northern South America

“…Singapore (Ng et al 1993), Canada (Coker et al 2001), China (Ma et al 2003), Hawaii (Mundy 2005), Poland (Solarz 2005), Australia (Hammer et al 2012;ACTFR 2014), USA (Robins et al 1991;Fuller et al 1999;Nico et al 2019;Rodríguez-Barrera et al 2020), and Italy (Lorenzoni et al 2019) and (2) Astronotus crassipinnis (Heckel, 1840). Type locality Rio Paraguay, distributed naturally in southern parts of the Amazon (upper Madeira River) and the upper Paraguay basins (Kullander 1986;Lasso et al 2001;Kullander 2003;Fricke et al 2019;Dos Reis et al 2020) and introduced in Bahia and São Paulo States, and the upper Paraná River in Brazil (Kullander 1981;García et al 2018;Lopes et al 2022). Kullander (1986) reviewed the taxonomy of Astronotus species based on morphometric and meristic data from 68 specimens from the Paraguay River basin (Paraná River basin in Paraguay), 18 specimens from several tributaries of the Amazon River basin (Brazil), six specimens from the Orinoco River Basin (Venezuela and Colombia), and 50 from the Peruvian Amazon (Ucayalí and Amazon basins); with this work he redescribed A. ocellatus and revalidated A. crassipinnis.…”

“…Singapore ( Ng et al 1993 ), Canada ( Coker et al 2001 ), China ( Ma et al 2003 ), Hawaii ( Mundy 2005 ), Poland ( Solarz 2005 ), Australia ( Hammer et al 2012 ; ACTFR 2014 ), USA ( Robins et al 1991 ; Fuller et al 1999 ; Nico et al 2019 ; Rodríguez-Barrera et al 2020 ), and Italy ( Lorenzoni et al 2019 ) and (2) Astronotus crassipinnis (Heckel, 1840). Type locality Rio Paraguay, distributed naturally in southern parts of the Amazon (upper Madeira River) and the upper Paraguay basins ( Kullander 1986 ; Lasso et al 2001 ; Kullander 2003 ; Fricke et al 2019 ; Dos Reis et al 2020 ) and introduced in Bahia and São Paulo States, and the upper Paraná River in Brazil ( Kullander 1981 ; García et al 2018 ; Lopes et al 2022 ).…”