Diets and Trophic Structure of Fish Assemblages in a Large and Unexplored Subtropical River: The Uruguay River

Abstract

The Neotropics represent a hotspot for freshwater biodiversity with vast number of fish species of scarce ecological knowledge. This hold true for the Uruguay River, where fish assemblages and their diets remain unexplored. Fish assemblages were surveyed in 14 sites along its main course, from headwaters to mouth (approximately 1800 km), with the aim to identify the trophic roles of fish and to describe trophic structure of these assemblages. Following standardized samplings, diet was determined to perform a trophic classification of species. One hundred species (2309 gut contents) were analysed and classified into four trophic groups subdivided into eight lower-level groups: Piscivore, piscivore-invertivore, detritivore, omnivore-detritivore, omnivore-invertivore, omnivore-planktivore and omnivore-herbivore. The trophic structure of the assemblages varied along the river, with the relative species richness of fish consuming terrestrial invertebrates increasing towards the middle river section, probably driven by the large floodplains in that areas, supporting global theories such as flood pulse concept. This study describes the feeding habits of fish along the Uruguay River, being the first dietary description for 29 species. This knowledge is essential for management and conservation, serving as baseline in the context of future environmental changes and generates novel evidence about the functioning of ecosystems in this scarcely studied climatic region.

Long‐term study of the reproductive timing of the Neotropical catfish Iheringichthys labrosus (Lütken, 1874): Influence of temperature and river discharge

“…However, limited information about the reproductive behaviour of low dispersal—or even nonmigratory species—such as I. labrosus is available. Iheringichthys labrosus may play a key role in the ecosystem as prey, owe to their high abundances in the studied sites and its trophic role (bentivorous) López‐Rodríguez et al, ). This in addition to the restricted available information about factors triggering reproduction in I. labrosus emphasise the contribution of this study in the largely unstudied Lower Uruguay River.…”

Trophic level and position of Pterygoplichthys pardalis in Ciliwung River (Jakarta, Indonesia) ecosystem based on the gut content analysis

“…However, the availability of food resources is one of the factors that influence the existence of fishes. Previous studies have also established that a correlation exists between the structure of the digestive apparatus and the feeding habits of fishes (Pereira et al 2016;Lopez-Rodriguez et al 2019;Manna et al 2020).…”

“…In addition, it relates to the availability of diet resources and the environmental state of the water. The trophic level of an animal is influenced by the composition of its diet and the trophic level of each food fraction of which data is obtained from analyzing its stomach contents (Zardo and Behr 2016;Carvalho et al 2017;Zainordin and Hamid 2017;Lopez-Rodriguez et al 2019).…”

Short-Term Interactive Effects of Experimental Heat Waves and Turbidity Pulses on the Foraging Success of a Subtropical Invertivorous Fish

“…We used Gymnogeophagus terrapurpura Loureiro, Zarucki, Malabarba and González-Bergonzoni 2016, (Perciformes: Cichlidae) as the predator and Hyalella curvispina Shoemaker 1942 (Crustacea: Amphipoda) as the prey. We choose G. terrapurpura because it is one of the most abundant fish in Uruguayan aquatic systems [37,38]. It has a wide distribution throughout the lower Uruguay River basin (in south-eastern South America, subtropical climate), where it has been recorded in different habitats including shallow lakes, floodplain lakes, rivers, and streams [39].…”

“…This small cichlid is also representative of the most common fishes in the Neotropical region, where fish assemblages are primarily composed of small-sized species, which use vision as their primary source of environmental information [37,41,42]. Also, G. terrapurpura is an omnivore-invertivore, feeding on zooplankton, macroinvertebrates and periphyton [38,43]. Feeding activity is sharply reduced during the autumn and winter when water temperature decreases [43,44].…”