Responses of fish assemblages of sandy beaches to different anthropogenic and hydrodynamic influences

Abstract

This study tested whether some attributes of the diversity, communities and populations of surf-zone fish assemblages varied with different hydrodynamic and anthropogenic influences at four Guanabara Bay sandy beaches: Dentro (sheltered with limited human access), Fora (exposed with limited human access), Urca (sheltered with unlimited human access) and Vermelha (exposed with unlimited human access), between autumn 2011 and summer 2012. Twenty-nine species and 1613 individuals were recorded from 76 trawls. The 10 most abundant species accounted for 94·5% of the total number, but only four species (Diplodus argenteus, Harengula clupeola, Sardinella brasiliensis and Sphoeroides greeleyi) were recorded at all four beaches, revealing a high level of species substitution. Fish assemblages differed not only for diversity attributes, but also at community and population levels, with lower values of the Shannon-Wiener index, richness and total fish abundance and biomass at Vermelha beach, and higher densities of Trachinotus carolinus, Atherinella brasiliensis and S. greeleyi related to beaches with high anthropogenic influence. The findings reveal that fish assemblages of Dentro, Fora, Urca and Vermelha beaches differed not only in response to hydrodynamic influences, but also due to the effects of different degrees of human interference (i.e. presence of solid residues, population density and fishing impacts), emphasizing the importance of the sheltered and less anthropogenically affected beaches, as spawning, nursery and growth areas.

The ecology of fish in the surf zones of ocean beaches: A global review

“…Fishing has changed the abundance, diversity and composition of surf fish assemblages in Australia, Brazil, Portugal and South Africa (Cabral et al., ; Clark et al., ; Franco, Ramos Chaves, Castel‐Branco, & Neves Dos Santos, ; Mualeque & Santos, ; Parker et al., ). Two studies correlate changes in fishing practices with variation in fish abundance over multiple years (7 years, Bennett, , 20 years, Rishworth et al., ).…”

The influence of size on the trophic interactions between juveniles of two syntopic Trachinotus species

“…inner bay) and oceanic (i.e. outer bay) waters (Franco et al ., 2016; Souza et al ., 2018). These beaches are predominantly composed by fine sand (Catanzaro et al ., 2004), differing from each other regarding wave exposure and anthropogenic pressure.…”

“…Seasonal dietary variations were not assessed in this study, as previous authors have reported that seasonality plays a minor role in the feeding of Trachinotus species (Helmer et al ., 1995; Niang et al ., 2010). In addition, no spatial pompano dietary variation was evaluated, as the surveyed beaches are close to each other (<2 km) and under the influence of very similar physical and chemical water conditions (Franco et al ., 2016), thus being considered a single beach system, among which these species would migrate.…”

“…Dentro beach (22°56 ′ 34 ′′ S 43°09 ′ 33 ′′ W) is ∼100 m long, with a smooth slope, and is the most sheltered from wave action, which rarely reaches >0.25 m height (Souza et al, 2018). Fora and Dentro beaches are also located inside the São João Fortress, a military complex with limited access to bathers and fishers, in contrast to Vermelha beach, which is intensively used by the local population (Franco et al, 2016).…”

“…Five species have been recorded in the Brazilian coast, of which Trachinotus cayennensi Cuvier, 1832, occurs exclusively in the north-east shelf, while the other four are found along the entire coast. The Florida pompano Trachinotus carolinus (Linnaeus, 1766) and the great pompano Trachinotus goodei Jordan & Evermann, 1869 are the most abundant species in beaches in south-eastern Brazil, where they benefit from a variety of food resources and protection against predators during most of the annual cycle (Niang et al ., 2010; Palmeira & Monteiro-Neto, 2010; Franco et al ., 2016; Souza et al ., 2018). These morphologically similar species have a strong competitive potential, as a high degree of niche overlap has been reported for their juveniles (Vaske-Junior et al ., 2018).…”