Fish taxonomic and functional diversity in mesohabitats of the River Kakada, Caura National Park, Venezuela

Abstract

The Caura National Park encompasses the entire basin of the River Caura, one of the most biodiverse hydrographic systems of Venezuela, yet the ichthyofauna, particularly in the upper basin, has been poorly studied. In this study, the taxonomic and functional diversity of fishes in mesohabitats of the River Kakada, a main tributary of the upper River Caura in Southern Venezuela, are described. The fishes were sampled in four mesohabitat types with seines during four different occasions, representing the hydrological seasons of rising waters, high waters, falling waters and low waters. Functional diversity indices were calculated based on four traits: size, trophic guild, mouth orientation and body shape. A total of 56 fish species were registered. There were significant differences in species composition of the fish assemblages and their taxonomic diversities among mesohabitats and across hydrological seasons, and the taxonomic and functional diversities were higher in the mesohabitats with presence of riparian forest. However, there were no seasonal variations in functional composition or functional diversities. The rocky substrates had unique assemblages of habitat specialist species with a particular array of traits. On the other hand, the presence of riparian forest and more structurally complex substrates favors the coexistence of a high diversity of fishes with a variety of trait combinations, whereas the seasonal fluctuations in the water level might propitiate stochastic processes of dispersion and colonisation that generate variations in species composition and taxonomic diversity. Considering the spread of artisanal gold mines in the Caura National Park, the results of this investigation might serve as a reference for future studies that assess the impacts of the gold mining activities on the river integrity and their fish communities.

Keywords

• diversity seasonal patterns
• fish assemblage structure
• fish traits
• Guiana Shield
• riverine flooded forest