Isotopic niche of the catfishes Bagre bagre and Genidens barbus in a coastal area of south-eastern Brazil

Abstract

The isotopic niche of Bagre bagre and Genidens barbus target of commercial fisheries in a marine coastal area from northern Rio de Janeiro State (~21ºS), south-eastern Brazil was compared to evaluate the feeding assimilation and the trophic relationship. The mean isotopic values of the catfishes and their food items in the δ13C-δ15N space were coherent with their respective trophic positions. The relative contributions of the food items highlighted the shrimp Xiphopenaeus kroyeri as the most assimilated item in the diet of B. bagre, while for G. barbus the model highlighted the fish Porichthys porosissimus. The absence of niche overlap together with the trophic evenness point to a reduced feeding overlap between B. bagre and G. barbus in northern Rio de Janeiro State.

The trophic ecology of marine catfishes in south-eastern Brazil

“…The present study corroborated using a stable isotope approach to classify marine catfish trophic guilds as omnivorous, as previously determined by stomach contents and stable isotope studies (Chaves & Vendel, 1996; Denadai et al ., 2012; Tavares & Di Beneditto, 2017; Di Beneditto et al ., 2018; Di Beneditto & Tavares, 2019). In south-eastern Brazil, Denadai et al .…”

“…To reduce the uncertainty in the interpretation of the mixing model, the potential prey were reduced/grouped to a total of five sources, similarly to the previous study of Di Beneditto et al . (2018).…”

“…In this sense, we calculated TEF 15 N and TEF 13 C based on equations from a meta-analysis of isotopic studies that considered muscle of fish species (Caut et al ., 2009) (Δ 15 N = −0.281 δ 15 N + 5.879 and Δ 13 C = −0.248 δ 13 C−3.4770). The calculated values for our data were + 1.8 ± 0.2‰ for TEF 15 N and + 0.5 ± 0.2‰ for TEF 13 C, similar to those of marine catfishes of the same region (Di Beneditto et al ., 2018).…”

“…Along the coast of São Paulo and Rio de Janeiro, their spatial distribution in estuarine systems is governed by salinity (Bizerril, 1999; Denadai et al ., 2012). They usually have wide trophic niches that, in general, overlap with each other's (Bruton, 1996; Denadai et al ., 2012) as many other sympatric fish species (Svanbäck et al ., 2015; Cachera et al ., 2017), and have been classified as generalist opportunistic omnivorous predators, with crustaceans, fishes, molluscs, annelids, detritus and algae commonly observed as the main groups of food items (Chaves & Vendel, 1996; Denadai et al ., 2012; Pinheiro-Sousa et al ., 2015; Tavares & Di Beneditto, 2017; Di Beneditto et al ., 2018; Di Beneditto & Tavares, 2019).…”

“…The amount of information generated by stomach assessments by scientists all over Brazil report the high importance of fishes and invertebrates (mainly crabs) as prey items of ariids (Chaves & Vendel, 1996; Denadai et al ., 2012; Tavares & Di Beneditto, 2017). To date, the trophic ecology of marine catfishes has been intensively studied over the last two decades (Chaves & Vendel, 1996; Bizerril, 1999; Denadai et al ., 2012; Pinheiro-Sousa et al ., 2015; Tavares & Di Beneditto, 2017; Di Beneditto et al ., 2018; Di Beneditto & Tavares, 2019). However, few studies off the Brazilian coast have focused on isotopic tracers (Giarrizzo et al ., 2011; Claudino et al ., 2015; Pereyra et al ., 2016; Di Beneditto et al ., 2018), and no data are available regarding stable isotopes coupled with Hg analyses in marine catfishes.…”