Population structure of the seahorse Hippocampus reidi (Syngnathiformes: Syngnathidae) in a Brazilian semi-arid estuary

Abstract The longsnout seahorse (Hippocampus reidi) is a vulnerable species found along most of the Brazilian coastline, such as semi-arid estuaries with strong rainfall seasonality, hypersalinity, and low depth. To evaluate the population structure of H. reidi over time, we monitored the seahorse population in the Pacoti estuary (Brazil) for one year, based on 248 registered specimens. Salinity, water transparency, sex, pregnancy, body height, and holdfast use were registered. Mixed linear models revealed that sampling month, salinity, and transparency had no influence on population density in the lower zone of the estuary. Pregnant individuals were more frequent in the dry season and at higher salinities. Mean body height (12.7 cm) increased in the dry season. Bright colors were predominant. The seahorses employed nine types of holdfasts, most often mangrove roots, and were found to reproduce throughout the year, peaking in the dry season. Salinity and transparency did not impact population density. In Brazilian semi-arid estuaries, the longsnout seahorse is strongly associated with mangrove vegetation, used as holdfast. Therefore, the conservation of seahorse populations depends on the conservation of the local mangrove forests

Ichthyofauna of two reservoirs in the middle Acaraú river basin, Ceará, Northeastern Brazil

Few studies have been published on the taxonomy, biology and ecology of the fish fauna of the rivers and reservoirs from the Brazilian Caatinga. Considering the importance of fish surveys as subsidies for future studies and fishing resources management, the purpose of the present study was to assess the fish assemblage of the two largest reservoirs in the middle Acaraú river basin, the Paulo Sarasate and the Edson Queiroz reservoirs, state of Ceará, Northeastern Brazil. Eight nycthemeral samplings were performed with gillnets (mesh size ranging from 3 to 12 cm between opposite knots) during rainy and dry season between 2010 and 2012. We captured 1,626 specimens belonging to three orders, nine families and 17 species, six of which are endemic to the Caatinga. Approximately 30% of the species observed were non-native and had been introduced for stocking purposes

Length-weight relationships for freshwater fish species from humid forest enclaves at the Brazilian semiarid

We report the length-weight relationships (LWR) for 11 fish species inhabiting headwater streams in the Araripe and Ibiapaba plateaus, Brazilian semiarid. Values of r2, a and b ranged respectively from.953 to.998, 0.010 to 0.043 and 2.81 to 3.69. Our reports on LWR are pioneer in humid forest enclaves at the Caatinga biome. Such enclaves of forest can be a checkpoint to climate change, but are under strong human pressure and remain under low investigation. © 2017 Blackwell Verlag GmbH

What governs the functional diversity patterns of fishes in the headwater streams of the humid forest enclaves: environmental conditions, taxonomic diversity or biotic interactions?

The relationship between functional and taxonomic diversity is a major issue in ecology. Biodiversity in aquatic environments is strongly influenced by environmental gradients that act as dispersion and niche barriers. Environmental conditions act as filters to select functional traits, but biotic interactions also play a role in assemblage structure. In headwater streams, the relationship between functional and taxonomic diversity remains unclear. In this study we investigated how environmental conditions, taxonomic diversity and biotic interactions influence the spatial distribution of traits and functional diversity in stream fish species. Standardized sampling of fish species was carried out in 50 m sections of 16 streams located in rainforest enclaves in a semiarid region of Brazil (Caatinga biome). The functional diversity indices displayed different responses to the predictor variables used. Functional richness was mainly influenced by environmental conditions, while functional evenness was mostly determined by taxonomic diversity. On the other hand, functional dispersion was explained by a combination of environmental conditions and taxonomic diversity. The spatial distribution of fish species with the same functional traits was random, indicating that biotic interactions are not a strong predictor in these ecosystems. Channel width, pH and substrate were the most important variables in the spatial distribution of the functional traits of the fish species. Our results suggest that the functional structure of fish assemblages in headwater streams depends mainly on environmental conditions and taxonomic diversity. © 2017, Springer Science+Business Media Dordrecht

Fish fauna from the estuaries of Ceará state, Brazil: a checklist in support of conservation of the Brazilian semiarid coast

We provide extensive surveys in eight estuaries along the coast of Ceará State in Northeastern Brazil, including local samples and data compiled from online data bases and literature. Samplings resulted in a checklist of the estuarine fish fauna, which recorded 126 fish species, and provides original information of some estuaries. Most of the sampled marine species are widely distributed and many are important commercial species for the artisanal fisheries. The addition of records from existing inventories and online collections increases the number of species to 245, of which 11 are threatened (critically endangered or vulnerable) and six are introduced. Our study provides an updated list of fish species of the estuaries along the semiarid coast of Brazil and is intended as a subsidy for further research, conservation and management efforts