Estado de conservação da ictiofauna continental no Ceará, Brasil

Abstract

Information about composition, distribution, population characteristics, and endemism is essential for developing a Red List of Threatened Species, a fundamental tool for biodiversity conservation actions. Aiming to characterize the state of conservation based on IUCN (International Union for Conservation of Nature) criteria of freshwater fish species occurring in the Ceará State (CE), we conducted an inventory of the continental ichthyofauna of the CE using available literature and data from the ichthyological collections of the Federal University of Rio Grande do Norte (UFRN) and the Federal University of Paraíba (UFPB). The minimum convex polygon (MCP) methodology was used to obtain the extent of occurrence (EOO) and area of occupancy (AOO) of each species Eighty-five freshwater fish species belonging to 59 genera, 25 families, and eight orders were recorded in CE. Among the orders, Characiformes stood out with 47% of the species and Siluriformes 32%. The remaining orders (six) comprised approximately 20%. Among the families, Characidae accounted for 19% of the species, Loricariidae 15%, and the others 66%. Of the total native species, 43 (51%) are endemic to the Caatinga. Based on IUCN methodology, 44 species were considered Least Concern (LC), four Near Threatened (NT), 17 were threatened, 15 presented insufficient data for analysis (DD), and five species were not applicable for evaluation (NA). Among the 17 species considered at risk of extinction, five were classified as Vulnerable (VU), five as Endangered (EN), and seven as Critically Endangered (CR). Among the most threatened groups of fish, the family Rivulidae, from temporary or perennial wetlands, stand out. Of the 81 species with georeferenced location records, 25 occur in a single basin, 23 in two or three basins, and 33 in four or more basins. The Metropolitan and Salgado basins presented the highest species richness (44 and 39, respectively). In contrast, the Serra de Ibiapaba and Curu basins had the lowest richness (6 and 17 species, respectively), indicating wide variability among the 12 evaluated basins (average 25,1 ± 10,3) and the need for greater sampling efforts. The basins with the highest relative number of threatened fish species were the Metropolitan, Litoral, and Baixo Jaguaribe basins, with seven, four, and two species, respectively. No species were found to be common among the three basins. It is concluded that there are serious risks to the maintenance of freshwater fish biodiversity in CE due to large projects with the potential to cause impacts in the areas of influence of the main hydrographic basins, necessitating mitigation programs. The creation of conservation units that include action plans for the protection and recovery of the most threatened species and studies to resolve taxonomic and under-sampling problems is urgently needed.