Fishes in the Brazilian Semi-arid
Alexandre Clistenes de Alcântara Santos & Angela Maria Zanata
The hydrographic network of the Brazilian Semi-arid (Introduction) is modest when compared to other Brazilian regions. It presents peculiar features, such as being intermittent and seasonal. However, this does not apply to all rivers in the caatinga; the main ones, São Francisco and Parnaíba, are perennial rivers  . Besides, there are mid-sized perennial ones which have their sources in the Chapada Diamantina, such as the Paraguaçu, Contas and Itapicuru. These rivers have intermittent tributaries and flow to the Atlantic Ocean after crossing large areas of the semi-arid land.
The species of fish that occurs in the Semi-arid are the result of evolutionary processes driven by climatic factors and by the hydrologic regime of the region. However, human influence through environmental changes and the introduction of alien species might have modified the very structure of the original fauna. Nowadays, around 240 species have been registered in this biome  , but this number is supposed to increase once efforts to survey hydrographic basins in the semi-arid region also increases. In the last years, UEFS has carried out a significant research work focusing this region, taking part and coordinating projects aimed at acquiring further knowledge on its biodiversity. In what it concerns the ichthyofauna, the UFBA and the UFPB have also carried out expeditions and scientific activities dealing with fishes in the Semi-arid. It is here presented a brief comment on the present stage of knowledge of the ichthyofauna in the Brazilian Semi-arid. Recent or yet ongoing works are briefly discussed and suggestions for future studies about the ichthyofauna of the region are made.
Current Knowledge of the Ichthyofauna in the Brazilian Semi-arid
Although inventories of ichthyofauna in the Brazilian Semi-arid began in the 19 th century (list of expeditions), knowledge on the diversity and the taxonomy of most aquatic environments in this region is still incipient . Despite the importance of knowing the ichthyofauna of the NE Brazil, most expeditions and works accomplished in the first half of the 20 th century present taxonomic problems such as wrong identifications, inadequate descriptions, lack of accuracy on the origin of the material, or have had only part of the samples scientifically analyzed. Recent studies have increased the knowledge on the ichthyofauna mainly through sampling and descriptions of species and, systematic reviews, quotations and compilation of literature on fishes from the region. Only recently, the first workshops on diversity, conservation, ecology and the origin of the fauna in the Semi-arid have been accomplished.
Around 240 species of fish occur in the Brazilian Semi-arid. Although the region is less diverse when compared to other regions in Brazil, it presents at least 56 endemic species. The total number of species registered for the main basins (e.g., São Francisco and Parnaíba) might be underestimated due to problems in determining which species do come from the Semi-arid, since these rivers have part of their courses out of the region. The lack of accuracy in the knowledge of the ichthyofauna is also due to the lack of surveys in river sources and the lack of precise information on the systematics and distribution of most taxa. Knowledge on the state of conservation of species has also been considered scarce since only four species have been classified as endangered  . However, most of the ichthyofauna has not yet been assessed.
Recently, a series of programs supporting the study of ichthyofauna biodiversity in the Semi-arid have been carried out: (i) studies in the Espinhaço Range have produced a list of species and assessment of conservation in the area under study; (ii) IMSEAR (Chapter 1) has defined priority basins to be surveyed through comparative studies among the drainages in the Semi-arid; (iii) PPBio of the Semi-arid (Chapter 2) has created a network of inventories; increased and modernized scientific collections in the NE Brazil; promoted theme studies on reproductive aspects of mid Paraguaçu River and, fomented on the formation of specialized professionals in the region; (iv) ‘ The Paraguaçu and Itapicuru Catfish Expedition ’ has sampled areas scientifically little explored in search for new species of fishes and samples of rare species for trying to solve taxonomic problems; (v) survey on the species of fish in the basins of Inhambupe, Itapicuru and Real deals with species from the shore mouths of rivers which have part of its course in the semi-arid region.
Projects on the Ichthyofauna in the Semi-arid
‘Studies on the Flora and Fauna from the Espinhaço Range of Bahia and Definition of Strategies for Conservation’ (CNPq): This project was coordinated by UEFS and had as its main objective to perform surveys of the fauna and flora in the region of the Chapada Diamantina, Bahia, besides elaborating strategies for the conservation of the area and its species. Its main results on the ichthyofauna were presented in a doctorate dissertation in zoology at the National Museum in Rio de Janeiro  . This work registered 63 species in 36 places of the upper Paraguaçu River. Ten new specie were identified, two of which (Myxiops aphos and Aspidoras psammatides) were described   , and two others are in the process of description. Among the main threats to the local ichthyofauna we can list the destruction of riverbed vegetation by mechanized mining of diamond in the past and the replacement of native forests for grazing land nowadays. Another important threat is the presence of exotic species from other South American basins which endanger native species.
Suggestions of possible actions of management and conservation of rivers and fishes in this region require (i) the implementation of long term projects; (ii) the recognition of how important this environment and its ichthyofauna is; (iii) support for the implementation of research nuclei focusing on the maintenance of biodiversity and environmental education, besides (iv) the support for programs for the conservation of native vegetation.
IMSEAR (MCT) : A study on the present state of knowledge on the ichthyofauna of the Semi-arid of the State of Bahia was carried out between 2003 and 2005 through the biodiversity program of IMSEAR. It was accomplished having the material from the collections deposited at Museu de Zoologia – UEFS, Museu Nacional do Rio de Janeiro and Museu de Zoologia – USP as basis.
Data on the occurrence of fishes in 43 municipalities were collected. That corresponds to about 16.47% of the total number of municipalities in the Semi-arid of Bahia. Data on species from the São Francisco River and other important basins in the State, such as the Paraguaçu and Contas were collected. Other important rivers which are part of the East basin such as Itapicuru, Vaza-Barris and Pardo Rivers as well as their tributaries were also included in this research.
A total of 239 species were registered, 21 of which are annual fishes from temporary lakes in the semi-arid land. Ten alien species were registered. This work has increased the number of species recorded for the São Francisco and East basins to 29 species.
Comparative analysis of the fauna of the basins shows low level of similarity between the fauna of the São Francisco and East basins which is probably related to a greater length and number of species in the first one. Among rivers in the East basin, the Paraguaçu is worth noticing for its number of species and for the increased knowledge we have acquired on its ichthyofauna in recent years. High similarity between the Contas, Pardo and Vaza-Barris Rivers is related to the low number of species registered in them, maybe a result of our little knowledge on their ichthyofauna. On the other hand, the Itapicuru River presents a high number of exclusive species which makes it a singularity among the rivers in the East basin.
Considering the results of the project, it can be inferred that the low number of species in the Contas, Pardo and Vaza-Barris Rivers is related to our little knowledge of the basins in the region under study, which reinforces the need of research on the ichthyofauna of these rivers. On the other hand, the high number of species exclusively distributed in the Itapicuru River emphasizes the importance of its basin and makes further research on its ichthyofauna urgent. This can prevent species from getting extinct even before being described.
Results accomplished by IMSEAR for the main rivers in the East basin emphasize the need of a better understanding of the basins of Contas, Pardo, Itapicuru and Vaza-barris Rivers , as well as parts of the middle and low Paraguaçu River.
PPBio of the Semi-arid (MCT) : This project aims at continuing biodiversity studies started by IMSEAR. It coordinates activities among several institutions, mainly in the NE Brazil . In what it concerns to the ichthyofauna, the project aims at producing a diagnostic of the present knowledge on the biodiversity of fishes in the Semi-arid in two years. The activities scheduled for the first year are:
(i) Inventories: a review of the literature on the ichthyofauna of the region is being concluded. Meanwhile, areas of extreme biological importance are being inventoried and new areas will be progressively added during the development of the project. Sampling focuses on the rain season (November-March), but sampling during the dry season (April-October) will also be carried out.
(ii) Collections: the process of digitizing the collection of the Fish Section at the Museu de Zoologia – UEFS and other important collections in the NE will continue aiming at making information available on the internet.
(iii) Theme Studies: The project has developed systematic studies for the description of new species; on the composition of the ichthyofauna of the region and, on reproductive aspects of fishes from middle Paraguaçu River . Actions on the conservation of aquatic ecosystems of the region will be carried out. These will support sustainable harvesting of fishes and the consequent maintenance of fishing stocks of the Semi-arid.
The Paraguaçu and Itapicuru Catfish Expedition: Funded by the National Science Foundation, USA , through the program ‘All Catfish Species Inventory’, this expedition was coordinated by UFBA. It had as the main objective sampling areas previously scarcely surveyed in search for new species of fish and material from rare species for phylogenetic studies which will help solve taxonomic problems. Its team included six researchers from UFBA, UEFS and USP. Field work was carried out in July 2005, reaching 37 places in the courses of the Paraguaçu, Jacuípe and Itapicuru Rivers , mainly in the sources and small tributaries. Over 8,000 specimens were sampled making up 59 species. Several new species were collected and are being described. Important information and material from endemic species were also collected. It is worth mentioning siluriform species, such as Conorhynchusconirostris, Parotocinclus bahiensis, Pimelodella bahianus and Kalyptodoras bahiensis. The later is an endangered species which is currently theme of a study on its distribution and ecology funded by Fundação Biodiversitas.
Survey on the Species of Fishes from the Basins of the Inhambupe, Itapicuru and Real Rivers: This project was developed as part of the Program for Regional Scientific Development by CNPq, via UFBA. It aims at surveying the species of fishes from the courses of rivers in the costal region of Bahia to the North of Salvador; describing new species; defining priority areas for conservation and, producing a catalogue for the species in the region. Most of the rivers sampled have part of their courses in the semi-arid region, seasonal regime and are highly anthropicised. Sampling was carried out in the period of 2004-2005 and found 53 species of fish from fresh water. Among these, five are probably new and the description of two of them (a new species of Hyphessobrycon and another of Parotocinclus) is being carried out. Further information on the distribution of species was also collected. Species such as Mimagoniates cf. sylvicola previously known to exist only in the South of Bahia were registered in the area under study.
Final Considerations
Information gath ered from the literature and partial results of the study indicate the extreme need of elaborating inventories of the ichthyofauna in the Brazilian Semi-arid followed by the analysis of the material collected under new systematic reviews. It is also recommend urgent actions for the conservation of fish biodiversity in the Semi-arid since several aquatic ecosystems and basins are under pressure over almost all areas. Ongoing studies hosted mainly by UEFS and UFPB have produced important contributions for both the elaboration of inventories and the definition of strategies for conservation. Besides that, we expect that present programs of incentive for the knowledge of biodiversity in the NE Brazil continue producing significant results for the understanding of the dynamics of the Brazilian Semi-arid as well as information that can effectively help environmental conservation in the region.
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