02/08/2026
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Researchers presents an inventory of the ichthyofauna from the blackwater habitats of the Coastal Plain in northern Santa Catarina, southern Brazil. In total, 30 species were recorded, representing 13 families and five orders. The authors found the entire study area is highly fragmented, with restinga remnants surrounded by urban zones and industrial infrastructure. This pattern of fragmentation reduces population connectivity, impairs gene flow, and increases the risk of local extinctions.
"The continued degradation of riparian vegetation, combined with climate change, poses an additional threat to the persistence of these communities. These findings underscore the urgent need to expand conservation actions targeting blackwater ecosystems along the southern Brazilian coastal plain."
Ichthyofauna checklists and rapid assessments are important tools for biologists, researchers, conservationists, and government bodies/NGOs. They provide critical baselines for the conservation and management of regional fish fauna. Our understanding of species composition in a territory evolves due to species movements across borders, extinctions, introductions, and new taxonomic evidence.
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Fish assemblages and endemism in blackwater aquatic habitats of the Coastal Plain in northern Santa Catarina, southern Brazil
Open-access - https://www.scielo.br/j/bn/a/hCWmq8GcxYnGmtQLbpNBHfJ/
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Dalcin, R. H., Lima, A. O. de S., Laaf, Y. de O., Ossa-Guerra, L. E. D. la ., Dallabona, J. A., Costa, V. S. C. da ., Abilhoa, V., Pinheiro, P. C., Feltrin, C. R., & Cionek, V. de M.. (2026). Fish assemblages and endemism in blackwater aquatic habitats of the Coastal Plain in northern Santa Catarina, southern Brazil. Biota Neotropica, 26(3), e20251834. https://doi.org/10.1590/1676-0611-BN-2025-1834
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Blackwater streams are unique environments characterized by dark, acidic, and nutrient-poor waters, supporting highly specialized aquatic communities.
This study presents an inventory of the ichthyofauna of such systems in the northern region of Santa Catarina state, based on surveys conducted between 2020 and 2024. A total of 22 sites were sampled, including perennial rivers, intermittent streams, and temporary pools, located both within and outside protected areas. In total, 30 fish species were recorded, representing 13 families and five orders. The order Characiformes showed the highest richness and was represented mainly by small-characins of the family Acestrorhamphidae. Nine species were identified as endemic to blackwater environments of the Atlantic Forest, five of which officially listed as threatened. The guppy ๐๐๐๐๐๐๐๐ ๐๐๐ก๐๐๐ข๐๐๐ก๐ was recorded for the first time in blackwater environments of the region, as well as ๐ต๐๐๐โ๐ฆโ๐ฆ๐๐๐๐๐๐ข๐ ๐๐. ๐๐๐๐๐, representing the first record of Hypopomidae (knifefish) in the region. DNA barcoding (using COI) provided molecular information, in addition to the morphological identification of 12 species, providing new local sequences for them. Results indicated a high similarity between the ichthyofauna of this region and that of blackwater streams in the southern coast of Sรฃo Paulo. Endemic and threatened species were recorded both inside and outside legally protected areas, highlighting gaps in current conservation efforts. Furthermore, intermittent streams and temporary pools proved to be critical habitats for maintaining species with extremely restricted distributions.
The continued degradation of riparian vegetation, combined with climate change, poses an additional threat to the persistence of these communities. These findings underscore the urgent need to expand conservation actions targeting blackwater ecosystems along the southern Brazilian coastal plain.
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Top left - Representative species of the order Characiformes recorded in the blackwater streams of northern Santa Catarina, Brazil. (A) Astyanax lacustris. (B) Deuterodon ribeirae. (C) Hollandichthys multifasciatus. (D) Hyphessobrycon igneus. (E) Hyphessobrycon griemi. (F) Hyphessobrycon reticulatus. (G) Oligosarcus hepsetus; (H) Psalidodon laticeps. (I) Rachoviscus crassiceps. (J) Characidium lanei. (K) Hoplias malabaricus. (L) Spintherobolus ankoseion. ( M ) Mimagoniates lateralis. ( N ) Mimagoniates microlepis. The white scale bar below each photograph corresponds to 1 cm.
Top right - Representative species of the order Cichliformes and Cyprinodontiformes recorded in the blackwater streams of northern Santa Catarina, Brazil. (A) Geophagus iporangensis. (B) Saxatilia lepidota. (C) Phalloceros cf. circummontanus (male). (D) Phalloceros cf. circummontanus (female). (E) Phalloceros spiloura (male). (F) Phalloceros spiloura (female). (G) Poecilia reticulata (male). (H) Poecilia reticulata (female). (I) Atlantirivulus haraldsiolii (male). (J) Atlantirivulus haraldsiolii (female). (K) Atlantirivulus luelingi (male). (L) Atlantirivulus luelingi (female). ( M ) Campellolebias chrysolineatus (male); ( N ) Campellolebias chrysolineatus (female). The white scale bar below each photograph corresponds to 1 cm.
Bottom - Examples of sampling sites visited during fieldwork activities. (A) Saรญ Mirim River, Itapoรก. (B) Tributary of the Saรญ Mirim River. (C) Temporary pool on the margins of the Saรญ Mirim River during the rainy season. ( D ) Temporary pool on the margins of the Saรญ Mirim River during the dry season. (E) Acaraรญ River, Sรฃo Francisco do Sul. (F) Tributary of the Acaraรญ River. (G) Temporary pool on the margins of the Acaraรญ River. (H) Pernambuco River, Barra do Sul. (I) Tributary of the Pernambuco River. (J) Perequรช River, Barra do Sul. (K) Tributary of the Perequรช River. ( L ) Temporary pool on the margins of the Perequรช River. (M) Tributary of the Itapocu River, Araquari. ( N ) Temporary pool on the margins of a tributary of the Itapocu River. (O) Cardoso Stream, tributary of the Itapocu River, Araquari. (P) Tributary of the Cardoso Stream.
ยฉ 2026 the Author(s). Published in the journal Biota Neotropical. An open-access article, distributed under the terms of the Creative Commons Attribution 4.0 International (CC-BY-4.0) deed. https://creativecommons.org/licenses/by/4.0/