Abstract
Ichthyological studies in coastal basins of the Mid-Northeastern Caatinga ecoregion were first conducted in the early 20th century, including collections from the Ceará-Mirim River basin, in northeastern Brazil. Besides a few systematics and ecological studies, the knowledge on fishes from this watershed is still considered partial and restricted to the freshwater portion. Thus, the objective of this paper was to conduct a comprehensive ichthyological survey of the entire Ceará-Mirim River basin, from the headwaters to the estuarine area. Fish surveys were conducted from 2011 to 2016 using varied fishing gear, resulting in the record of 63 native species (24 freshwater, 15 estuarine, and 24 marine species) and two introduced species. Four species are putatively endemic to the ecoregion, and 48 consist of new records for the basin. According to the Brazilian’s threatened fish list, three species are currently classified as ‘vulnerable’ (Megalops atlanticus, Hippocampus reidi and Mycteroperca bonaci), four as ‘near threatened’ (Kryptolebias hermaphroditus, Dormitator maculatus, Lutjanus sygnagris and L. jocu) and three as ‘data deficient’ (Cheirodon jaguaribensis, Mugil curema and Sphoeroides testudineus). The Ceará-Mirim River basin does not have any protected areas and has been suffering multiple anthropogenic impacts, however the "Centro Tecnológico de Aquicultura" (Aquaculture Technological Center) of the Universidade Federal do Rio Grande do Norte (CTA/UFRN) at the lower portion of the basin may help in the conservation of the estuarine and estuarine fish species.
Highlights
The Mid-Northeastern Caatinga freshwater ecoregion (MNCE) located in the extreme northeast Brazil comprises the drainages between the largest perennial rivers of the region, the São Francisco and Parnaíba (Albert et al 2011, Rosa et al 2003)
One of the basins draining into the eastern coast of the MNCE is the Ceará-Mirim River basin, in the Rio Grande do Norte State, and presents an intermittent hydrological regimen in the upper and medium portions, while the lower stretch, located in the Atlantic Forest area, is perennial
Specimen collections were conducted along 11 sampling sites (S01-S11) (Table 1, Figure 1) from the upper to the lower Ceará-Mirim River basin, and resulted in the record of 62 fish species, including two non-native (Oreochromis niloticus and Poecilia reticulata) (Table 2, Figure 2)
Summary
The Mid-Northeastern Caatinga freshwater ecoregion (MNCE) located in the extreme northeast Brazil comprises the drainages between the largest perennial rivers of the region, the São Francisco and Parnaíba (Albert et al 2011, Rosa et al 2003). Most of its rivers are intermittent due to the predominance of the semi-arid climate (Rosa et al 2003) Their margins usually present xeric shrublands and thorny forests of the Caatinga vegetation, except for the humid highland enclaves (Rosa and Groth 2004), and for a narrow strip of land running along the eastern coast of Brazil that harbors fragmented remnants of Atlantic Forest. One of the basins draining into the eastern coast of the MNCE is the Ceará-Mirim River basin, in the Rio Grande do Norte State, and presents an intermittent hydrological regimen in the upper and medium portions, while the lower stretch, located in the Atlantic Forest area, is perennial This particular basin is of historic importance due to the "Stanford Expedition" specimen collection conducted in 1911. Samples from this basin were taken in 1933 by the "Departamento Nacional de Obras Contra Secas – DNOCS", in an effort by the "Comissão Técnica de Piscicultura do Nordeste do Brasil", institution managed by Rodolpho von Ihering, to study the region’s ichthyofauna (Canan 2011)
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