Abstract
This study evaluated feeding patterns and ontogenetic variations in a non-native fish species (Plagioscion squamosissimus) in an isolated lake in the Upper Paraná River floodplain. Quarterly samplings were performed from April 2005 to February 2006 using plankton nets to capture larvae, seining nets for juveniles, and gill nets and trammel for adults. Stomach contents (n = 378) were examined according to the volumetric method in which the volume of each food item was estimated using graduated test tubes or a glass counting plate. During early development (larval stage), P. squamosissimus consumed mainly Cladocera and Copepoda. Juveniles showed a more diverse diet, including shrimp (Macrobrachium amazonicum), fish, aquatic insects (Trichoptera, Ephemeroptera, Chironomidae and pupae of Diptera) and plants. It was notable the high proportion of cannibalism (23.3%) in this stage. Adults consumed predominantly shrimp and fish. The use of food resources varied significantly between development stages (ANOSIM; r = 0.458; p<0.005), showing changes in food preferences during ontogeny. The Similarity Percentage Analysis (SIMPER) indicated that Cladocera and Copepoda were responsible for the differences observed between the larval stages of pre-flexion, flexion and post-flexion. M. amazonicum and Chironomidae were responsible for the differences between juvenile and larval stages, while M. amazonicum and other fishes caused the differences between adults and other ontogenetic stages. These results are confirmed by the relationship between standard length and developmental periods (ANCOVA; r2 = 0.94; p<0.0001). In general, there were low values of trophic niche breadth. The essentially carnivorous habit from the early stages of P. squamosissimus and the predominant use of M. amazonicum by adults have important roles in feeding patterns of the species, suggesting a major contribution to its success and establishment, especially in lentic environments.
Highlights
IntroductionPlagioscion squamosissimus, Heckel, 1840, (Sciaenidae, Perciformes), commonly known as curvina, is considered carnivorous in its natural habitat in the Amazon basin
Plagioscion squamosissimus, Heckel, 1840, (Sciaenidae, Perciformes), commonly known as curvina, is considered carnivorous in its natural habitat in the Amazon basin. This species was introduced into northeastern Brazil, and was subsequently released by the Energy Company of São Paulo (CESP) in 1967 in the Pardo River where it spread throughout the Paraná River basin [1, 2, 3]
The rarefaction curve was asymptotic to each ontogenetic stage sampled, suggesting that the number of individuals analyzed was sufficient to represent the diet of each stage (Fig 2)
Summary
Plagioscion squamosissimus, Heckel, 1840, (Sciaenidae, Perciformes), commonly known as curvina, is considered carnivorous in its natural habitat in the Amazon basin. The significance of this species in the Upper Paraná River, given by its high abundance in regions of the Itaipu Reservoir [8, 9] and in several environments of the floodplain upstream, including environmental protection areas like the Parque Nacional de Ilha Grande [10, 11] and the Parque Estadual das Várzeas do Rio Ivinhema [12], places this species in a prominent position, especially because of its economic importance and ecological interactions In this context, it becomes essential to address its biological characteristics, especially its feeding habits in all stages of the life cycle. Studies on the biology of non-native species in protected areas became relevant, mainly when considering biological invasions with consequent fauna homogenization as one of the main threats and causes of biodiversity loss [14, 15]
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