Abstract
Abstract: Amazonian floodplain lakes host a high diversity of predatory fish which coexist and exploit the high diversity of available prey. Morphology could be the characteristic most closely associated with their preferred feeding sources (prey). However, it is unclear whether this association is direct or indirect. If it is indirect, swimming performance or preferential position in the water column could be the most evident characteristic. To examine the degree to which fish morphology of predator fish species is correlated to their dietary inputs, we compared the existence of morphological and feeding dissimilarity among eight predator species with the association between predator morphologies and preferred prey. We collected, measured, and sampled the stomach contents of fish from two lowland floodplain lakes associated with the Solimões River, Brazil, in May, August, and November of 2014. Of 187 collected fish across eight species, five species showed fish to be the most important item in their diets and three preferentially ate shrimp. Principal components analyses of ecomorphological attributes divided the species according to their ability to find the prey, swimming performance of the predator, and prey size. While there was significant distinction between the varying morphologies of predators, we were unable to distinguish between the specific diet of these species and did not find a correlation between morphology and feeding. These results are likely due to the fact that there is great abundance and diversity of available prey in the Amazonian floodplain lakes, so opportunistic feeding may be the primary foraging strategy of predator fish species living in these environments.
Highlights
The Amazon basin displays strong spatial heterogeneity (LoweMcConnell 1999) coupled to marked seasonal changes associated with the hydrological cycle (Junk et al 1989)
The environmental changes of the Amazonian floodplain areas are dictated by variations in water level, have been associated with the life history strategies of fishes living in these areas (Sanchez-Botero et al 2003, Anjos et al 2008, Correa et al 2008, Duarte et al 2010)
We aim to fill these research gaps by addressing the following questions: Is there a correlation between morphology and diet of Amazonian predator fish? Do predatory fish uniformly share the feeding items? Are the ecomorphological characteristics similar among predator fish species? There are two opposing processes that potentially mediating the coexistence of these predatory species which could be identified with the answer to these questions: (i) the availability of prey is limited and predators need to develop strategies to avoid a over-predation of some specific preys, where in turn we would expect a high correlation between morphology and diet; and (ii) the availability of prey is high and fish morphologies are determined by phylogenetic process
Summary
The Amazon basin displays strong spatial heterogeneity (LoweMcConnell 1999) coupled to marked seasonal changes associated with the hydrological cycle (Junk et al 1989). Amazonian fish evolved to display several morphological, behavioral, and physiological adaptations to successfully exploit the habitats of floodplain areas (Val & Almeida-Val 1995, Freitas et al 2010), including areas of open-water, macrophyte meadows, and flooded forests. Each of these habitats change greatly over the year as a consequence of the flood pulse (Junk et al 1989) and subsequently show perceptible effects on fish assemblages (Siqueira-Souza et al 2016a). These environmental changes determine food availability (Soares et al 1986, Winemiller 1989, Mérona & Rankin-de-Mérona 2004, Carvalho et al 2017)
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