Improving the characterization of fish assemblage structure through the use of multiple sampling methods: a case study in a subtropical tidal flat ecosystem

Abstract

The use of multiple sampling gears is indispensible to obtain robust characterizations of fish assemblage structure in species-rich subtropical ecosystems. In this study, such a dependence was demonstrated by characterizing the structure of the high-tide fish assemblage in a subtropical tidal flat ecosystem (the Araçá Bay, southeastern Brazil) using eight different gears along five seasonal surveys and estimating the bay's fish species richness, combining these data with those from local tide pool fish surveys. The high-tide fish assemblage was spatially structured, contained five threatened species, and was dominated by persistent and large populations of Eucinostomus argenteus and of the fisheries species Mugil curema and Diapterus rhombeus that intensively use the bay throughout their life cycles. Large, small-bodied fish populations supported a regular use of the bay by piscivores. The autumn-winter peak in abundance of juvenile fishes caused a subsequent increase in piscivore abundance, and both events explained the bulk of the seasonal variability of the fish assemblage. The estimated richness revealed that the combination of sampling methods was enough for sampling the bulk of the local richness, and the bay may hold a surprisingly high richness compared to other costal ecosystem of the region. This faunal characterization, only viable using multiple gears, will be critical to support the implementation of a future study to monitor the impacts on local fish biodiversity of an imminent port expansion over the tidal flat.

Ecosystem modeling as a framework to convert a multi-disciplinary research approach into a useful model for the Araçá Bay (Brazil)

“…Handling it produced an estimated mean sampled area of 378 ± 153 m 2 . Details about sampling surveys and each gear are explained in Supplementary Material (Table SM1) and Contente and Rossi-Wongtschowski (2017).…”

Optimal fishing samplers to reveal the morphological structure of a fish assemblage in a subtropical tidal flat

“…Worldwide, coastal shallow sandy areas (including tidal flats) are recognized as important nursery and growth grounds for fish (Gillanders et al, 2003;Adams et al, 2006;Favero, Dias, 2015;Le Luheme et al, 2017). The peculiar presence of the small mangrove spots in Araçá Bay, the habitats heterogeneity and the advantageous hydrodynamics, provide shelter and food for juveniles of many species, including important commercial fishes, besides being a natural refuge for some globally considered threatened species, such as the snappers L. analis and L. cyanopterus, and the dusky grouper E. marginatus (Lamas et al, 2016;Contente, Rossi-Wongtschowski, 2017). Gibson (1994), Vasconcelos et al (2013), and Le Pape, Bonhommeau (2015) consider this kind of ecosystem as a nursery ground, and according to Sheaves et al (2014) and Nagelkerken et al (2015), this characteristic renders a substantial importance for its maintenance.…”

“…Details regarding samplings, gear design, and operation are described by Contente, Rossi-Wongtschowski (2017). However, we considered the encircling gillnet as two different gears because the same net was employed in distinct habitats (the inner shallow sublittoral and the marginal shallow sublittoral).…”

“…It acts as a link in coastal food webs, transferring energy from plankton and small organisms to larger fishes and other organisms positioned at higher trophic levels (Ganias, 2014). The higher phytoplankton concentration inside the bay than in adjacent areas (Ciotti et al, 2015) attracts clupeid and engraulid juveniles in high abundances, allowing larger piscivores to feed in the bay (Matsuura, 1998;Contente, Rossi-Wongtschowski, 2017). Also, high concentrations of mature sardine spawners are frequently found in the region surrounding the São Sebastião Island and the São Sebastião Channel (Fig.…”

“…The Araçá Bay (southeastern Brazil) is a tidal flat ecosystem (~ 500,000 m²) with highly diverse habitats occupied by more than 1,364 species, with 56 novel species catalogued, as well as 16 threatened species (Amaral et al, 2015). The latter including ten benthic species (three polychaetas, five echinoderms, and two enteropneustas); one bird, the royal tern (Thalasseus maximus (Boddaert, 1783)), which reproduces on the Brazilian coast exclusively in São Paulo State (Yorio, Efe, 2008); one sea turtle, Chelonia mydas (Linnaeus, 1758); and five marine fishes, including the dusky grouper (Epinephelus marginatus), the mutton snapper (Lutjanus analis), the cubera snapper (Lutjanus cyanopterus (Cuvier, 1828), and two rays, the chola guitarfish valid as Pseudobatos percellens (Walbaum, 1792) and the spiny butterfly ray (Gymnura altavela (Linnaeus, 1758)) (Amaral et al, 2010;Amaral et al, 2015;MMA, 2014;Lamas et al, 2016;Contente, Rossi-Wongtschowski, 2017).…”