The coexistence of fish species in streams: relationships between assemblage attributes and trophic and environmental variables

Abstract

Diet overlap and niche breadth are wellknown species traits from trophic ecology that can assist in explaining how species interact and coexist as well as the ecological mechanisms that influence biodiversity. In the present study, we analyzed the relationships between these trophic variables and indicators of resource availability with some attributes of fish assemblages (species richness, Shannon diversity index, evenness, density and individual body size). The physical and chemical characteristics of the biotopes (topography, water quality and conservation of slopes) were examined to identify possible patterns. Monthly sampling using electrofishing was conducted in 2003 along five streams located in the Cuiabá River watershed. The relationships between environmental variables and attributes of fish assemblages were evaluated using Spearman correlation. Species richness and abundance varied among streams, with higher values (54 and 82 species) found in low-gradient streams that drained small swampy areas discharging in Cuiabá River. Diet overlap showed significant and negative correlations with species richness, the diversity index, abundance, variation in body size and food availability and positive correlations with evenness and niche breadth. Environments that had greater food availability had a reduced variety of food items (smaller amplitude) and distinct values in terms of dietary overlap. Nevertheless, to explain resource partitioning in a fish assemblage (overlap), it is necessary to consider food availability and niche breadth (degree of trophic specialization) beyond the interaction of these variables with species richness and density. In conclusion, high diversity and abundance values were strongly associated with a high degree of trophic specialization (low amplitude of trophic niche) and a small degree of overlap in the diet.

Prey diversity as a driver of resource partitioning between river‐dwelling fish species

“…The present study reveals that food resource partitioning between salmon and bullhead can vary within a river system, between sites at relatively short distances from each other, and between seasons at a given site, with resource partitioning being strongly dependent on prey diversity at different sites. Studies on other species have given indication that high prey diversity may enhance food resource partitioning (see, e.g., Hillebrand & Shurin, ; Jiang et al., ; Martin & Garnett, ; Zapata et al., ) and that competition for food is high when prey diversity is low (Barili et al., ; Hillebrand & Shurin, ; Targett, ). Our study corroborates these findings and supports the notion that high prey diversity may promote consumer coexistence through food resource partitioning.…”

“…For example, Barili et al. () reported that high fish abundance and diversity can promote trophic specialization in sympatric species, thereby enhancing food resource partitioning, and density‐dependent foraging behavior may occur when resources are limited (Sánchez‐Hernández & Cobo, ). Noteworthy, our interferences regarding the influence of density dependence on the competition for food should be taken with some caution because our analyses included the overall fish density regardless of fish size.…”

“…Alternatively, if prey diversity is low, sympatric species may utilize the same resources, and niche overlap will be high or competitive exclusion could occur (Keddy, ; Schoener, ). The potentially important relationship between prey diversity and dietary overlap between sympatric species has rarely been explored, but the few examples that exist from fish (Barili, Agostinho, Gomes, & Latin, ; Targett, ; Wuellner et al., ) and other vertebrates (Jiang, Feng, Sun, & Wang, ; Martin & Garnett, ; Zapata, Travaini, Delibes, & Martinez‐Peck, ) indicate that increased prey diversity may mitigate competition through enhanced resource partitioning (but see Wuellner et al., ). It should, however, be kept in mind that variables other than prey diversity, such as prey abundance, foraging mode, diel patterns, and habitat segregation for feeding, may also be major determinants of food resource partitioning (e.g., Crow, Closs, Waters, Booker, & Wallis, ; Kronfeld‐Schor & Dayan, ; Nakano, Fausch, & Kitano, ; Sánchez‐Hernández, Vieira‐Lanero, Servia, & Cobo, ).…”

<b>Co-occurrence patterns of fish communities in littorals of three floodplain lakes of the Orinoco River, Venezuela</b>

“…Recent models have assumed that communities are randomly assembled (Hubbell 2001); however, evidence from freshwater fish communities in tropical floodplains highlights the importance in their organization of factors such as biotic interactions (Winemiller 1996;de Mérona & de Mérona 2004;Barili et al 2011), species-habitat associations (Peres-Neto 2004;Rodrigues et al 2013) and environmental filtering (Rondón Suárez et al 2004;de Melo et al 2009). …”

Summer co‐existence of small‐sized cyprinid and percid individuals in natural and impounded stretches of a lowland river: food niche partitioning among fishes

“…The guild structure does not only incorporate food type (prey items), but also foraging habits and foraging habitats. The guild structure of an ecosystem is often more stable in time than its species composition, because the species within a guild can take over each other's functional role, following slight fluctuations in environmental conditions (Aarts & Nienhuis, 2003;Barili et al, 2011).…”