Trophic ecology of Acestrorhynchus falcirostris Cuvier, 1819 in island lakes on the lower stretch of the Solimões River, Amazon Basin.

F Corrêa,F K Siqueira-Souza,C E C Freitas,J Aguiar-Santos,C Lubich

doi:10.1590/1519-6984.253852

Abstract

The aim objective of this study was to determine the trophic ecology of juvenile and adult Acestrorhynchus falcirostris during the rising and flood (high-water) period in six island lakes adjacent to the Solimões River. As such, we investigated: i) the trophic position, through the fractional trophic niche; ii) the niche breadth; iii) niche overlap and iv) the food strategy of the species. The specimens were collected during the years 2014 to 2017, using gillnets with mesh sizes ranging from 30 to 120mm between opposite knots. Through the analysis of stomach contents, the preference in the consumption of items of animal origin was observed. Juveniles consumed insects in greater proportions (IAi% = 50%), while adults consumed fish (IAi%=99,98%). Despite the large supply of food items available in the high-water period, juveniles were the only ones to consume items of allochthonous origin, such as insects. Juveniles presented a different dietary strategy and dietary composition to adults. Juveniles were omnivores with a generalist strategy, while adults were piscivores with a specialist strategy. Thus, the food composition, niche breadth, trophic position and feeding strategy of Acestrorhynchus falcirostris change due to the stage of development.

Highlights

In lakes of the Amazon floodplain, food items and habitat availability are directly and indirectly influenced by the flood pulse (Junk et al, 1989)
The high-water period provides an increase in the diversity of food items, in which fish species, including those of predatory fish, benefit from the quantity and quality of available items
Due to competition for food, the degree of dietary variation is influenced (Araújo et al, 2011; Svanbäck et al, 2011), and influencing dietary composition, and other trophic aspects, which can be verified by the niche breadth (Krebs, 1998), trophic level (Amezcua et al, 2011), niche overlap (Pianka, 1973) and feeding strategy

Summary

Introduction

In lakes of the Amazon floodplain, food items and habitat availability are directly and indirectly influenced by the flood pulse (Junk et al, 1989). The high-water period provides an increase in the diversity of food items, in which fish species, including those of predatory fish, benefit from the quantity and quality of available items Because of the alterations in the supply of food items caused by the predictable fluvial dynamics, some species present high food plasticity and exploit a wide variety of prey, while others tend to be more specialist and consume only one or a few types of prey These different eating patterns are can occur at the inter-and intra-specific level, in this last relationship, for example, influenced by the stage of development of individuals of the same species (Ward et al, 2006). These changes occur to optimize foraging efficiency and increase individual performances (Bolnick et al, 2003; Svanbäck and Bolnick, 2008)

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