Changes of fish trophic guilds in Araruama Lagoon, Brazil: What can be inferred about functioning and structure of hypersaline lagoons?

Use of stable isotopes in the evaluation of fish trophic guilds from a tropical hypersaline lagoon

“…(2015) concluded that hypersalinity was not a predominant factor influencing the trophic ecology of fish in this lagoon, Saad (2003) and Cruz et al . (2018) suggested that species composition, biomass and, consequently, food web structure across the ecosystem were under influence of a gradient that separated species according to their tolerances to salinity variation. In hypersaline lagoons, salinity is considered to be the main abiotic factor known to influence fish composition (Vegas-Sandejas & Santillana, 2004; Deegan et al ., 2010), and changes in species and guild composition will influence the food web structure, leading to feeding (stomach contents) and isotopic variation (O'Farrell et al ., 2014; Houssain et al ., 2016; Rosa et al ., 2016).…”

“…A lower salinity year-round had been observed at site 1 (closer to the sea), with more constant, higher values at site 2 (Kjerfve et al ., 1996, Cruz et al ., 2018). These spatial trends regarding salinity were also observed herein, leading to a significant difference between sites (41.1 ± 3.3, 45.0 ± 1.7, Mann–Whitney U test, U = 186.5, Z = −4.37, P < 0.001, Table 1).…”

“…and the planktivorous O. glinum . The same was observed regarding polychaetes, suggested as the main food item for E. gula , and rare but still present for M. furnieri and O. glinum (Almeida-Silva et al ., 2015; Cruz et al ., 2018). Further analyses regarding prey assimilation by the fish species are necessary in order to properly correlate stomach contents and isotopic signatures.…”

“…Due to a low catch during summer, a temporal analysis was not possible and only a spatial data analysis was performed. Fish species were grouped in trophic guilds following previous work developed in the same area (Saad, 2003, Almeida-Silva et al ., 2015, Cruz et al ., 2018). For logistical reasons, it was not possible to collect other components of the food web.…”

“…These results are in agreement with analyses of stomach content data from previous studies from AL that showed the same prey items with varying relative importance among the most abundant species. For example, while crustaceans and molluscs were the main prey categories observed for M. furnieri (Cruz et al, 2018), they were less important but still present in the stomachs of the detritivorous Eucinostomus spp. and the planktivorous O. glinum.…”