Abstract
Abstract: We present here an embracing freshwater fish inventory of the Parque Nacional dos Lençóis Maranhenses and adjacent areas, reporting 49 fish species, 33 of which were identified accurately at the species level, representing ten orders and 25 fish families that range from obligate freshwater to estuarine organisms. This number of species is much larger than two previous studies for the park, each reporting just 12 and 33 fishes occurring on freshwater environments. Among the 49 freshwater species recorded in this study, 14 are new records for the Parque Nacional dos Lençóis Maranhenses, and just one corresponds to an introduced species. Some of the 14 new records in the Parque Nacional dos Lençóis Maranhenses, cited above, as well as some of the 16 species which we are not able to identify accurately at the species level, could include undescribed species, but more study is necessary before sorting out which species are truly undescribed, and which are already described ones. The orders reported by this survey which comprise the highest percentage of species richness, excluding introduced species, were: Characiformes, Cichliformes and Siluriformes, in the same ranking position, and Gymnotiformes, as expected for Neotropical freshwater surveys. The families with the highest number of species, excluding non-native species, were: Characidae, followed by Cichlidae, and Loricariidae. Out of the 33 species herein identified accurately at the species level, five of them are species typically found in brackish water environments, and when occurring on freshwater environments, are restricted mainly to estuaries, or, occasionally, the lower portions of the rivers. Thus, we will not address them in our biogeographical comments. From the remaining 28 species, eight did not occur in the Amazon River basin, six of them being endemic to the Maranhão-Piauí ecoregion. The remaining species herein reported also have their distribution recorded for the Amazon River basin, which shows the great influence of the Amazon basin. In the last two decades efforts to inventory the freshwater fish fauna and to taxonomically solve some groups occurring on the Maranhão state have been made. However the knowledge regarding the composition of the Maranhão freshwater fishes is still insufficient and underestimated, with several groups still lacking adequate taxonomic and systematic resolution, and with many gaps of knowledge, something that is not appropriate for our current picture of "biodiversity crisis". As well as, the other Brazilian protected areas, the PNLM fails to preserve its freshwater environment properly, since it includes only fragments of the major river systems of the area, not including and conserving the hole river drainages, mainly excluding their headwaters. Thus, its water bodies are exposed to typical human impacts.
Highlights
South America presents a rich ichthyofauna, with an estimative of more than 9,100 valid species occurring in freshwater and marine environments of coastal areas
The fish survey of the freshwater rivers of Parque Nacional dos Lençóis Maranhenses reported 49 species, representing 10 orders and 25 fish families that range from obligate freshwater to estuarine organisms
One of the few ichthyofauna studies conducted at the Parque Nacional dos Lençóis Maranhenses (PNLM) was the paper published by Garavello et al (1998) which provided a preliminary list of fishes occurring on the sand dune lagoons of the park
Summary
South America presents a rich ichthyofauna, with an estimative of more than 9,100 valid species occurring in freshwater and marine environments of coastal areas (about 25% of all world fish species). The published Check List of Freshwater Fish from South and Central America (CLOSSFCA) (Reis et al 2003) listed about 4,500 valid species for the Neotropical region, estimating that there was still at least 1,550 undescribed species. Since the publication of CLOFFSCA, an average of 104 new species have been described every year in South America, totalizing 1,142 new species. About 28% of the ichthyofauna known in South America has been described in the last 11 years, according to Reis et al (2016)
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