A trait‐based approach reveals the feeding selectivity of a small endangered Mediterranean fish

Abstract

Functional traits are growing in popularity in modern ecology, but feeding studies remain primarily rooted in a taxonomic-based perspective. However, consumers do not have any reason to select their prey using a taxonomic criterion, and prey assemblages are variable in space and time, which makes taxonbased studies assemblage-specific. To illustrate the benefits of the trait-based approach to assessing food choice, we studied the feeding ecology of the endangered freshwater fish Barbus meridionalis. We hypothesized that B. meridionalis is a selective predator which food choice depends on several prey morphological and behavioral traits, and thus, its top-down pressure may lead to changes in the functional composition of in-stream macroinvertebrate communities. Feeding selectivity was inferred by comparing taxonomic and functional composition (13 traits) between ingested and free-living potential prey using the Jacob's electivity index. Our results showed that the fish diet was influenced by 10 of the 13 traits tested. Barbus meridionalis preferred prey with a potential size of 5-10 mm, with a medium-high drift tendency, and that drift during daylight. Potential prey with no body flexibility, conical shape, concealment traits (presence of nets and/or cases, or patterned coloration), and high aggregation tendency had a low predation risk. Similarly, surface swimmers and interstitial taxa were low vulnerable to predation. Feeding selectivity altered the functional composition of the macroinvertebrate communities. Fish absence favored taxa with weak aggregation tendency, weak flexibility, and a relatively large size (10-20 mm of potential size). Besides, predatory invertebrates may increase in fish absence. In conclusion, our study shows that the incorporation of the trait-based approach in diet studies is a promising avenue to improve our mechanistic understanding of predator-prey interactions and to help predict the ecological outcomes of predator invasions and extinctions.

Dynamic competition and resource partitioning during the early life of two widespread, abundant and ecologically similar fishes

“…Bray-Curtis similarity matrices (Bray & Curtis, 1957) were calculated using the abundance (square-root transformed) of each taxon in the diet of each fish and ordinated (group centroids with trajectories) using non-metric multidimensional scaling (MDS) to investigate trophic niche overlap in roach and bream larvae in allopatry and sympatry (Clarke & Warwick, 2001). The matrices were tested for homogeneity of dispersions using permutational analysis of multivariate dispersions, and then submitted to permutational multivariate analysis of variance (PERMANOVA; 9999 random permutations) with pair-wise comparisons, using a two-way factorial design accounting for treatment (fixed factor, nested in time) and time (random factor), to assess the significance of any competition (differences in the trophic niches of allopatric and sympatric fish; Werner & Hall, 1976;Bolnick et al, 2010), and also differences between sampling occasions (Anderson, 2001;Anderson et al, 2008;Rodríguez-Lozano et al, 2016;Gilby et al, 2017). Mesocosm number was included as a random factor but had no effect, so data were pooled from each treatment for further analysis (Jackson et al, 2013).…”

“…The fish were stocked to coincide with a peak in zooplankton abundance and left to acclimatise for 3 days (cf. Rodríguez-Lozano et al, 2016;Krabbenhoft et al, 2017;Cano-Rocabayera et al, 2020). The stocking density (* 280 fish m -2 ) was within the range observed in the mainstem of a nearby lowland river (0-821 fish m -2 , summer mean 85 fish m -2 ; Nunn et al, 2007a), and the 1:1 ratio in the sympatry treatment was selected to test for asymmetries in the competitive relationship (Young, 2004).…”

A network meta‐analysis of threats to South American fish biodiversity

“…Meanwhile, 268,940 tons of plastic were discarded into the sea (Eriksen et al, 2014), causing the "South Atlantic garbage" drifts in the ocean (Ryan, 2014). However, a complete estimate of the associated pollution is lacking (Rodríguez-Lozano et al, 2016).…”

“…Changes in the environment due to the exploitation of the largest rhodolith bed in the southern Atlantic Ocean extirpated benthic species and associated fish (Brasileiro et al, 2016). Mining increased substantially the fish mortality in South America (Rodríguez-Lozano et al, 2016;Wenger et al, 2017). In freshwaters, it resulted in the worst environmental disaster in Brazilian history when the Bento Rodrigues dam collapsed in the Doce River basin, killing 19 persons and tons of fish, in 2015 (Neves, Nunes, de Carvalho, & Fernandes, 2016).…”

Peer Review #1 of "Trait-based predation suitability offers insight into effects of changing prey communities (v0.1)"

“…Manuscript to be reviewed Usseglio-Polatera, 2002;Rossberg, Brännström & Dieckmann, 2010;Nagelkerke & Rossberg, 2014;Rodríguez-Lozano et al, 2016) through prey vulnerability traits, predator foraging traits, and the interaction of both prey and predator traits (Klecka & Boukal, 2013;Green & Côté, 2014;Spitz, Ridoux & Brind'Amour, 2014).…”