Fishes from the coastal basins of the Mid-Northeastern Caatinga ecoregion (MNCE) were first sampled by the Stanford expedition at the beginning of the 20th century, and published by Edwin C. Starks in 1913. This material included specimens from the Papary lake (= Papari lagoon) in the lower portion of the Trairí river basin, draining towards the eastern coast of Rio Grande do Norte State. In 1941, Henry Fowler provided a broad taxonomic study of the freshwater fishes from northeastern Brazil, including material from the Papari lagoon, besides describing four species assigned to this locality. However, these previous surveys focused only in the lower portion of the Trairí river basin and might be incomplete. Given this framework, the present study aimed at perform a wide ichthyofaunal inventory of Trairí river basin and compared with previously surveys performed in the regions. In 2013 and 2014, four expeditions along the whole basin, including the Papari lagoon itself, resulted in 28 species of fishes belonging to 17 families and seven orders. At Papari lagoon area 16 species were registered whereas 26 and 18 species were recorded by Starks and Fowler’s studies, respectively. Considering all records, 50 species were documented in the basin with 14 (28%) new records, including Serrapinnus potiguar, whose distribution was extended to the south. Two species described by Fowler, Pimelodella papariae and Pseudancistrus papariae, were not found in this study or in any fish collection, and are only known from their type-material. These two species can be naturally rare, locally extinct, or there were inaccuracies in their type-locality. However, species of these genera are only found in larger basins of the MNCE, which drains to the north, corroborating the latter assumption. Although not being a definitive list, the recent extensive fish surveys conducted in the MNCE’s coastal basins are helping to elucidate species’ geographic distribution and little knowing taxonomic issues.

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The Rivulidae fish family, which includes Neotropical seasonal killifishes, is one of the most diverse taxonomic groups in the aquatic systems of Caatinga in Brazil. Cynolebias and Hypsolebias genera, with 20 and 35 endemic species, respectively, concentrate the greatest diversity of rivulid species in the semiarid. Sixty-eight years after the first records of annual killifishes in the Mid-Northeastern Caatinga ecoregion (MNCE), only four valid species have been sampled in this area. Here we combined bibliographic surveys and recent samplings to investigate the distribution of seasonal rivulids in MNCE. Twenty-one records were obtained, nine of which are new localities, expanding the distribution of three species: Hypsolebias martinsi, H. antenori and Cynolebias microphthalmus. Hypsolebias longignatus is still only known from its type locality in Ceará, near the Environmental Protection Area in Pacoti River, and has not been sampled ever since its description in 2008. Among the four species present in MNCE, H. antenori is the only species occurring within the limits of a conservation unit in the Furna Feia National Park. Anthropogenic impacts were observed in most temporary habitats visited, which ranged from river channel to small ponds in cave entrances. All records are found in coastal basins that discharge in the northern coast of the MNCE, in Ceará and Rio Grande do Norte states, which are crucial for the conservation of the Caatinga’s killifishes. The results also evidenced the importance of karstic habitats in the Jandaíra Formation as potential biotopes for seasonal fish in MNCE. This information must be used to update the conservation status of these species and highlight the importance of strategies for preserving the Caatinga’s temporary aquatic habitats, which should be considered for environmental licensing purposes.

The Nascentes do Rio Parnaíba National Park (NPNP), located in Brazilian Cerrado, protects portions of three river basins: headwaters of Parnaíba, a small portion in upper Tocantins-Araguaia, and tributaries of the middle section of the São Francisco. This protected area is in the boundaries of the states of Maranhão, Tocantins, Piauí, and Bahia, also known as MATOPIBA, a region that has established rapid agricultural expansion associated to land conflicts between corporate agriculture, family agriculture, protected areas, indigenous territories, and quilombola communities. The knowledge of the ichthyofauna in this region is scarce while the impacts on the aquatic environments are increasing. We made a survey of fishes in the NPNP and its surroundings areas, estimating richness, endemics, introduced and shared species between river basins. During 2014, 54 sampling sites were visited, 19 in the NPNP and 35 in the surrounding area. Ninety-five species, 51 genera, 22 families, and six orders were recorded, of which 38 (40%) are in the NPNP. One introduced species were recorded in the Parnaíba River basin and no endangered species were registered. Our data corroborate the importance of the network of protected areas for the preservation of Cerrado fishes, including some possibly undescribed and restricted-range species that may be threatened due to intense agricultural encroachment in the MATOPIBA region.

Microcambeva bendego, a small psammophilous catfish species, is described from the rio Guapi-Macacu basin at Guanabara Bay in Rio de Janeiro State, an Atlantic Forest remnant. This coastal drainage has been explored by several naturalists and fish researchers since the 19th century. It is a drainage with remarkably high endemism and species richness, and some recently-described and threatened species. The new species is distinguished from all congeners by two distinctive characters: long finger-like projections in the branchial isthmus and a large opercular patch of odontodes with 19 odontodes. Due to the paucity of specimens (n=3) osteological features of the new species were accessed by CT-Scan images of the holotype. Microcambeva bendego shares putative synapomorphies with two congeners, M. ribeirae and M. filamentosa, such as the fusion of supraorbital pore s6, the absence of ossification in the anterior autopalatine cartilage, the presence of an elongated and wide posterior process of the autopalatine, and a concavity on the dorsal process of the opercle. Those characters suggest that M. bendego is more closely related to those two species from the rio Ribeira de Iguape basin than to other congeners. The biogeography and conservation status of M. bendego are also discussed.