Fish Fauna and Environments of the Pilcomayo-Paraguay Basins in Formosa, Argentina

Home , Bermejo River, Formosa Province, Paraguay River, Piaractus mesopotamicus, Pseudoplatystoma, Rhinodoras dorbignyi

Fish fauna and environments of the Pilcomayo-Paraguay basins in Formosa, Argentina

Roberto C. Menni 1, Amalia M. Miquelarena 2, Hugo L. Lopez 2, Jorge R. Casciotta2 , Adriana E. Almiron & Lucila C. Protogino 2 1Laboratorio de Ictiologia, Museo de La Plata, Paseo del Bosque s/n, 1900 La Plata, Argentina; 2 Instituto de Limnologia de La Plata, 53 N 484, 1900 La Plata, Argentina

Received 16 July 1991; in revised form 1 April 1992; accepted 28 April 1992

Key words: fish zoogeography, ecology, water chemistry, faunistics, Argentina

Abstract

The ichthyofauna from subtropical (East) and tropical (West) areas in the Formosa province (North- ern Argentina) is analyzed. An up-to-date list of fishes is provided, including 18 new reports for environments associated with the Pilcomayo and Paraguay rivers, considering the detailed distribution of the fishes. Dominant families in terms of number of species are Characidae, Pimelodidae, Loricariidae and Curimatidae. Percentage of individuals (about 5000 examined) were 66% for characoids and 25% for siluriforms, with less than 10% for other groups. Comparisons were made with other South American environments. Most frequent species were Psellogrammus kennedyi, Astyanax bimaculatus, Gymnocorymbus ternetzi, Hoplosternum thoracatum and Cichlasomaportalegrense. The predominant type of environment sampled, of small size and shallow depth, with extensive plant cover, and temporal level variations, explains the dominance of the above groups. This interpretation is supported by independent studies. Diversity values ranged between 0.71 and 3.92. A marked reduction in number of species from East to West was observed (79 and 41 species respectively, 31 shared). No species of Gymnotidae, Hemiodidae, Characidiidae, Trichomycteridae, Lebiasinidae nor Aspredinidae were captured in the West. The higher number of species in eastern environments is considered to be due to the influence of the Paraguay river and the complex hydrology of the area. Other factors, both historical and ecological are considered. A correlation between total phosphorous content in the water and fish richness is also suggested. Water chemistry is compared with near by environments. Sites studied showed pH values from 6.14 to 7.5. The dissolved solid contents ranged from 51.8 to 474.3 mg 1- ', within the hypohaline level. Ionic composition differed somewhat between East and West, water in the East being mainly hypocalcic, as in the Paraguay river. Conductivity was rather variable and Secchi disk values similar to those in the Parana river.

Introduction Bermejo river to the South, the Paraguay river to the East, and about 64 ° W to the West (Figs 1 Formosa is a province in northeastern Argentina, and 2). Most of its territory is subtropical except between the Pilcomayo river to the North, the for a small NW sector within the tropical belt. 130

Fig. 1. Localities samples in Eastern Formosa (1-17 + 18 and 19 from MLP). The insert shows the Formosa province in Argen- tina, and the Eastern (1) and Western (2) areas. 131

the tropics, corresponds to the 28-29 C isotherm in summer (January the warmest month), and to the 17 C isotherm in winter (July the coldest month). The E zone has respectively the following values: 27-28 °C and 17 °C. Both areas are frost free over 340 days yr- . Total an- nual rainfall is between 700 mm y-' in the NW and 1100 mm y- 1 in the E. Bucher (1980) maintains that the most important factors for the terrestrial fauna (rainfall, sea- sonality, soil type) show a well defined E-W gradient which has a stronger influence over the biota than the weak N-S temperature gradient. The climate is subtropical with a dry season (in winter) at the center and in the West, and a small stripe without a dry season in the East (Chiozza & Gonzalez van Domselaar, 1958). Many ecological aspects of the area can be seen in Neiff (1986). The area studied belongs to the La Plata river Fig. 2. Localities (22-30) samples in western Formosa. basin, zoogeographically within the Paranoplat- ensean province in the sense of Ringuelet (1975). Though it is presumed to be a rich fish zone, available information about the number and iden- The territory of the province is part of an enor- tity of the fishes is fragmentary and scattered. The mous pluvial valley without elevations, so the re- most comprehensive data on the ichthyofauna of lief is determined by alluvial deposits. The general this area influenced by the Pilcomayo and Para- slope is in a NW-SE direction, with a similar guay rivers are provided by Ringuelet et al. (1967), pattern in the orientation of rivers and creeks. who reported 84 species from localities in For- The low slope conditions the water runoff. Ac- mosa. Other references have been provided by cording to Siragusa's (1975) hydrographic Lopez & Castello (1966), Castello et al. (1978), scheme, the lakes, 'lagunas' and salines of the Azpelicueta & Braga (1980), Lopez (1972, several area belong to the 'Chaquean' province, agreeing species) and Bayley (1973). Pignalberi de Hassan in general terms with other geographic and phy- & Cordiviola de Yuan (1988) provide a list of togeographic criteria (Bucher, 1980; Cabrera, 76 species (some synonyms excluded). 1976). Considering main characteristics of the For the present paper 30 aquatic environments soil, the NW section is called the Flooding zone related to the Pilcomayo and Paraguay rivers were of the Pilcomayo river (Fig. 2), and the E section surveyed in the Formosa province (Figs 1 and 2). the Eastern depression (Morgan, 1980) (Fig. 1). Samples are divided according to the above men- This eastern zone is, according to Neiff(1986), an tioned zones, with 6 localities in the Flooding extensive system of autochthonous rivers with a (Western) zone (Fig. 2) and 17 localities in the surface area of nearly 82 700 km 2. Within this area Eastern depression (Fig. 1). there are only two allochthonous rivers, the Pil- The aim of the paper is to provide an up-to- comayo and the Bermejo, which transport sedi- date list of the fishes occurring in the Formosa ments from the eastern slopes of the Andes. After province, analyse the distributions of 18 species Burgos (1970), who describes in some detail the which are new for the area, and to report and climate of the area, the NW zone, mainly within discuss limnological observations. 132

Material and methods Table i. (Continued)

The studied material Loc. 3. A man-made pond at the crossing of the national was gathered from: route 11 with the road to Tte. Gral. J. C. Sanchez ( = Riacho a) 23 localities sampled by the authors (RCM, He-He), 27 km far from Clorinda, Pilcomayo Dept. HLL, JRC) during August 1986 (steady wa- Loc. 4. * A man-made pond along the secondary road from ters at the end of dry period) and April 1988 the national route N 11 to Tte. Gral. J. C. Sanchez, km 884, (about the end of the rainy period). Of these, Pilcomayo Dept. Astyanax fasciatus, 1 spec., 27-VIII-90-2. Hyphessobrycon luetkeni, 1 spec., 20-IX-90-1. Moenkhausia 17 belong in the Paraguay and Pilcomayo riv- sanctafilomenae, 1 spec., 20-IX-90-2. Tridentopsis pearsoni, ers basins in the East of Formosa (Locs. 1 to 1 spec., 27-VIII-90-1. Apistogramma borelli, 3 spec., 24-VIII- 17, Fig. 1), and 6 belong in the Pilcomayo river 90-6. basin in the West of the province (Locs. 23 to Loc. 5. A man-made pond along the secondary road from the 28, Fig. 2). national route N 11 to Tte. Gral. J. C. Sanchez, km 892, Pil- b) 5 localities were obtained from material in the comayo Dept. Rhamdia cf. quelen, 2 spec., 24-VIII-90-7. collection of the Museo de La Plata (MLP), Loc. 6. A man-made pond along the secondary road from the collected before this work was done (Locs. 18 national route N 11 to Tte. Gra. J. C. Sanchez, km 896, Pil- to 22; 18 and 19 in the East, 22 in the West, comayo Dept. Astyanax fasciatus, 15 spec., 29-VIII-90-1. 20 and 21 imprecise so not on map). Hyphessobrycon luetkeni, 2 spec., 25-IX-90-1. Rhamdia cf quelen, 3 spec., 29-VIII-90-2. Tridentopsis pearsoni, 1 spec., c) 3 localities in the Pilcomayo basin, with ma- 25-IX-90-2. terial gathered by Toba-Pilaga indians from Loc. 7. A creek under the first bridge in the road from Tte- Vaca Perdida and El Churcal offered by Mr. . Gral. J. C. Sanchez to Colonia Pastoril, km 921, Pilcomayo Pastor Arenas (CONICET) (Locs. 23, 29, Dept. Astyanax fasciatus, 1 spec., 25-IX-90-3. Disichthys and 30). iheringi, 1 spec., 30-VIII-90-1. Moenkhausia intermedia, 1 spec., 25-IX-90-4. Samples of fishes which are new reports for the area are deposited at the MLP, together with de- Loc. 8. * A creek crossing the national route N 11, km 103, 36 km far from Clorinda, Pilcomayo Dept. Astyanaxfasciatus, tails of species and number of specimens caught 2 spec., 30-VIII-90-3. Hyphessobrycon luetkeni, 1 spec., 25-IX- at each locality. 90-5. Moenkhausia intermedia, 1 spec., 25-IX-90-6. Geographical information under each new re- M. sanctafilomenae, 4 spec., 30-VIII-90-5. Characidium port includes the most comprehensive references fasciatum, 3 spec., 30-VIII-90-4. Rhamdia cf quelen, 5 spec., and other of particular interest (A full references 30-VIII-90-2. list is not given for editorial reasons). Table 1 lists Loc. 9. * Riacho (small river) Timbo-Pora. Formosa Dept. localities and reference material. Poptella paraguayensis, 1 spec., 24-VIII-90-3. Astyanax fasciatus, 1 spec., 24-VIII-90-5. Disichthys iheringi, 2 spec., Table 1. List of localities and material examined of new 4-IX-90-1. Moenkhausia intermedia, 9 spec., 24-VIII-90-4. M. records. Other material still unnumbered at MLP collection. sanctafilomenae, 146 spec., 24-VIII-90-1. Rineloricaria cf. Asterisk denotes chemical data available. parva 2 spec., 24-VIII-90-2.

Loc. 1. * A creek in the national route N 11 (Formosa to Loc. 10. * Pilaga river, Formosa Dept. Clorinda), km 103, 36 km far from Clorinda, Pilcomayo Dept., Loc. 11. * A creek crossing the road to Pirane, km 230, 22 km in front of the entrance to Gendarmeria Nacional garrison. far from Formosa, Formosa Dept. Disichtys iheringi, 26 spec.: Astyanax fasciatus, 17 spec., MLP Coll. N 27-VIII-90-5. 12-IX-90-2. Rhamdia cf. quelen, 20 spec., 12-IX-90-3. Hyphessobrycon luetkeni, 9 spec., 27-VIII-90-3. Rhamdia cf: quelen, 2 spec., 19-IX-90-1. Tridentopsis pearsoni, 245 spec., Loc. 12. * A man-made pond on the road to Pirane, km 259, 27-VIII-90-4. 29 km far from Formosa, Formosa Dept. Parauchenipteruscf. ceratophysus, 1 spec., 13-IX-90-5. Tridentopsis pearsoni, Loc. 2. A man-made pond along the national route N 11, 35 spec., 12-IX-90-1. about 10 km from Clorinda, Pilcomayo Dept. Astyanax fasciatus, 1 spec., 19-IX-90-2. Moenkhausia intermedia, Loc. 13. * A creek 16 km far from Pirane (road from Pirane 1 spec., 19-IX-90-3. Hemiodus orthonops, 2 spec., 28-VIII- to Formosa), Pirane Dept. Rhamdia cf quelen, 1 spec., 25- 90-1. Characidiumfasciatum, 3 spec., 28-VIII-90-2. IX-90-7. 133

Table 1. (Continued) according to Shannon and Weaver (1963). Phys- icochemistry data were obtained according Loc. 14. A man-made pond near Monte Lindo Grande, For- to mosa Dept. Rhamdia cf. quelen, 1 spec., 25-IX-90-8. APHA (1971) methods. Loc. 15. * Channel crossing the national route N 11 (formosa to Clorinda), about 2 km from the crossing with the national route N 81, Formosa Dept. Apistogramma borelli, 1 spec., 13- Hydrography IX-90-4. Lepidosiren paradoxa, 1 spec., 13-IX-90-3. Loc. 16. A man-made pond along the national route 90 (Es- The lower Paraguay is a meandering river; 58% pinillo to Pirane), 8 km far from Espinillo, Pilagas Dept. of its alluvial plain surface is occupied by a recent Apistogramma borelli, 1 spec., 13-LX-90-2. meander plain. This unit is formed by closely Loc. 17. * Riacho (small river) El Malvao, crossing the na- spaced series of levees and shallow depressions tional route 90 (Espinillo to Pirane), 3 km far from Tres La- which show the successive slipping of the mean- gunas, Pilagas Dept. Astyanaxfasciatus. der banks; there are also oxbow lakes ('lagunas'), Loc. 18. Formosa City, Formosa Dept. Hyphessobrycon some of them large, which can be transformed luetkeni, 13 spec., MLP 9-VII-58-18, Coll. Dr. Max Biraben. into lotic environments during floods (Drago, Loc. 19. Paraguay river, Formosa City, Formosa Dept. 1975). In the lower section of the river, which Loc. 20. Formosa. Aphyocharax cf. nasutus, 3 spec., 8-IX- is about 62-9. Rhamdia cf. quelen, 2 spec., 8-IX-62-14. Coll. in both 700 m wide, the banks are low and water over- cases Arriguti. flows both margins during flooding, covering from Loc. 21. * Pond in the bank of the Paraguay river, Formosa 10 to 15 km. The river receives important tribu- Dept., MLP 6-VI-55-31, Coll. dr. Max Biraben. taries such as the left-bank Tebicuary and the right bank Pilcomayo and Bermejo Loc. 22. Ingeniero Juarez, Matacos Dept. (MLP 31-X-73-11, rivers. The 18-X-73-5, Coll. Dr. Axel Bachmann). sources of the Pilcomayo are between 4000 and 5000 m o.s.l. on the Bolivian plateau, with some Loc. 23. * Vaca Perdida, on the road from Pozo de Maza to ° Sombrero Negro, branches in Argentine territory between 19 and Bermejo Dept. Astyanaxfasciatus, 1 spec., ° 13-IX-90-1. 23 S and 64 and 67 °W. During low water (last- ing nine months a year), the river is interrupted Loc. 24. A depression produced by trucks in the road be- in tween Vaca Perdida and El Churcal, Bermejo Dept. the 'esteros' region, developing a landscape with large swamps and 'lagunas', generally temporary Loc. 25. * Esteros (swamps) from the Pilcomayo river at El Churcal, Bermejo Dept. because its waters still run over a single slope through low levees, undergoing evaporation and Loc. 26. Pond along the road from Ingeniero Suarez to Pal- infiltration to enrich ground waters. The Pilco- mar Largo, 20 km far from El Quebracho, Bernejo Dept. Rivulus sp., 1 spec., 13-IX-90-7. mayo regime includes summer flooding and long periods of low water during which it feeds in the Loc. 27. Pond at the El Quebracho road, at the crossing with the Petroleo road, Bermejo Dept. ground waters, drying out for only about fifteen days in October (Palese de Torre, 1958). Loc. 28. * Pond along the road from El Quebracho to Los Pocitos, Bermejo Dept. Loc. 29. La Rinconada, 80 km far from Ingeniero Suarez, Types of environments Bermejo Dept. Pterygoplichthys cf: multiradiata, 1 spec., 13- IX-90-6. Following Ringuelet (1962), the sampled environ- Loc. 30. River bed near Tres Yuchanes, Bermejo Dept. ments can be grouped in six different types: rivers, creeks, 'baflados de desborde', 'cafladas', Specimens were captured with moderate ponds in man-made depression and small lenitic amounts of Pronoxfish, trawl nets, gillnets, 'atar- water bodies. Rivers considered in this paper raya' and handnets. Reported temperatures refer (permanent courses over 5 m width), have slow to the time of fishing. Diversity was calculated current, smooth bottoms and sediments rich in 134 organic matter (Locs. 10 and 17). Samples creeks (Locs. 1, 7, 8, 9, 11 and 13) were permanent or semipermanent water courses less than 5 m width, with temperatures during the day from 17 to 20 C ( = 18 C, N= 5). Depths ranged from 1 to 1.2 m, with muddy bottoms, and Secchi disk values between 2 to 45 cm (See Martinez & Fru- tos, 1986). In Argentina the name 'bafiado' (a kind of marsh) is given to a semipermanent or temporary water body, lacking a defined perimeter and its own sediment, formed by the overflow of a near river or creek. These characteristics were found in Fig. 3. 'Esteros' from the Pilcomayo river at El Churcal a Pilcomayo river arm (Loc. 25) (Fig. 3), an en- (Loc. 25). vironment 1.5 m deep, fully transparent. 'Cafiada' (a type of brook) is a lowland biotope between two elevations, with transitory water and aquatic vegetation. We consider as this type locality 23 (Fig. 4), which is the only water resource manent or semipermanent. Their size did not ex- for the indians living in the neighborhood. Though ceed 25 m x 10 m, with a depth of about 0.5 to Ringuelet (1962) suggests the term may be use- 1.5 m. Temperatures ranged between 18 ° and less, it agrees closely with Loc. 23 characteristics: 28 C, lower in the eastern localities during Au- temperature from 22° to 26 C, and depth from gust, and highest in the West in April. Values of 1 to 1.5 m. Floating vegetation included Secchi disk ranged from 0.10 to 0.14 m. Some Limnobium laevigatum and the water hyacinth ponds showed a dense plant cover composed of Eichhornia azurea. Lemnacea and Ludwigia, with patches of E. a- Pignalberi de Hassan and Cordiviola de Yuan zurea and Polygonum hispida. (1988) reported depths from 0.20 to 2.45 m and Locality 24 (Fig. 5) was a 3 mx 5 m pond Secchi disk values from 0.09 to 0.35 m for 0.15 m deep, produced by trucks, inhabited by 16 ponds in eastern Formosa. two species of fish in spite of being 10 km far from Refering to the eastern area, Neiff (1986) re- any other water body. ported that the first and second order collectors expand repeatedly in wide flooded areas locally called baifados, esteros and cafladas. It must be noted that 'esteros' is a local name generally ap- plied to a tropical swamp as the typical Chaco- paraguayan water bodies studies by Carter & Beadle (1930). The lenitic environment receiving this name in Argentina, as the large Iberi system and the esteros in the Chaco and Formosa provinces, have their own limnological characteristics (Ringuelet, 1962; Neiff, 1981). Water bodies in localities 2 to 6, 12, 14 to 16, and 26 to 28 were in man-made depressions (See Ringuelet, 1962:73; Lowe McConnell, 1987:152). Placed at the side of the roads, they filled with rain water and are slowly invaded by vegetation, being per- Fig. 4. 'Cahada' at Vaca perdida (Loc. 23). 135

Table 2. Fish fauna from Formosa province environments. A: From previous sources (listed in text), B: From this study, C: Numbers caught. Asterisks denote new reports for the province. Undetermined species are included only when the genus is new for the province.

A B C

Potamotrygonidae Potamotrygon sp.

Characidae Raphiodon vulpinus Charax stenopterus Fig. 5. A depression in the road between Va Perdida and El Charax gibbosus x 41 Churcal (Loc. 24). Roeboides bonariensis x 3 Roeboides paranensis x 35 Roeboides prognathus Acestrorhynchus altus x 27 Cynopotamus argenteus Galeocharax humeralis Results and discussion Triportheusparanensis x 91 Salminus maxillosus x Faunistics Prionobramaparaguayensis Aphyocharax alburnus x 15 The most obvious approximation to knowledge of Aphyocharax anisitsi x 64 Aphyocharax dentatus the Formosa ichthyofauna is through Ringuelet Aphyocharax nasutus * et al. (1967a), which provides detailed lists of the Acrobrycon tarijae known localities of 84 species. There are also Pseudocorynopoma doriae some references in Ringuelet (1975), but these Poptella paraguayensis * 2 lack precision. Additionally, Lopez and Castello Astyanax f. fasciatus * 46 Astyanax lineatus (1966) reported Sternopygus macrurus from Ria- Astyanax abramis x cho de Oro, Castello et al. (1978) Corydoras Astyanax alleni x 2 hastatus for Formosa city neighborhood, Azpeli- Astyanax b. bimaculatus x 761 cueta and Braga (1980) found Curimatella alburna Astyanax bimaculatusparaguayensis caudimaculata( = C. cf. australis) in the Paraguay Ctenobrycon multiradiatus Gymnocorymbus temetzi x 368 river off Formosa, Lopez (1972) added Hemigrammus sp. Colossoma mitrei (= Piaractus mesopotamicus), Hyphessobrycon callistus x 7 Pseudoplatystoma fasciatum, Paulicea luetkeni, Hyphessobrycon luetkeni 17 Pimelodusalbicans and Raphiodon vulpinus for the Markiana nigripinnis x x 172 Bermejo River, and Bayley (1973) mentioned Moenkhausia dichroura x x Moenkhausia intermedia 12 Pseudoplatystoma coruscans for the Pilcomayo Moenkhausia sanctaefilomenae 159 river. Pignalberi de Hassan & Cordiviola de Yuan Psellogrammuskennedyi x x 502 (1988), in a paper about fish populations from Tetragonopterusargenteus x x 1 16 ponds associated with the lower Paraguay river Piabucus melanostomus x x 14 near the city of Formosa, provided a list of Odontostilbe piaba x x 382 Odontostilbe paraguayensis x x 25 76species. Excluding Loricaria typus (=L. Holoshesthes pequira x x 100 maculata), Aequidens paraguayensis( = Bujurquina vittata) and A. tetramerus (doubtful identity), Serrasalmidae 24 species remain which at the date of publication Serrasalmus marginatus x x 2 were new reports for the Formosa province. 136

Table 2. (Continued) Table 2. (Continued)

A B C A B C

Serrasalmus spilopleura x x 24 Doras eigenmanni x x 3 Serrasalmus nattereri x x 1 Pterodorasgranulosus x Piaractusmesopotamicus x Rhinodoras dorbignyi x Mylossoma duriventris x Trachydorasparaguayensis x Mylossoma orbignyanum x Mylossoma paraguayensis x Auchenipteridae Auchenipterus nigripinnis x Gasteropelecidae Auchenipterus nuchalis x Thoracocharax stellatus x Parauchenipteruscf. ceratophysus * 1 Parauchenipterusstriatulus x x 90 Erythrinidae Hoplerythrinus unitaeniatus x x 75 Aspredinidae Hoplias m. malabaricus x x 17 Disichthys iheringi * 29

Lebiasinidae Pimelodidae Pyrrhulina australis x x 73 Iheringichthys westermanni x x Pyrrhulinamacrolepis x Microglanis parahybae x x 15 Pimelodella gracillis x x 6 Anostomidae Pimelodella howesi x x 7 Schizodon f. fasciatum x x Pimelodella laticeps x x 1 Leporinus friederici x Pimelodus albicans x x Leporinus obtusidens x Pimelodus argenteus x x Pimelodus clarias maculatus x x Hemiodidae Pimelodus ornatus x Apareiodon affinis x x Rhamdia cf quelen * 118 Hemiodus orthonops * 2 Rhamdia sapo x Luciopimelodus pati x Curimatidae Hemisorubim platyrhynchos x Prochilodusplatensis x x Paulicea luetkeni x Steindachnerinabrevipinna x Pseudoplatystoma coruscans x Steindachnerinaconspersa x x 25 Pseudoplatystomaf. fasciatum x Cyphocharax voga x x 22 Sorubim lima x x Cyphocharax platanus x x Cyphocharax spilota * 154 Trichomycteridae Potamorhinasquamoralevis Tridentopsispearsoni * 434 Psectrogastercurviventris Xx Curimatella cf. australis x Callichthyidae Callichthys callichthys x x 70 Characidiidae Corydoras aeneus x x 182 Characidiumf fasciatum *6 Corydoras hastatus x x 8 Corydoras paleatus x Gymnotidae Corydoras microps x Gymnotus carapo x x 19 Hoplosternum littorale x x 19 Hoplosternum t. thoracatum x x 237 Rhamphichthydae Eigenmannia virescens x x 8 Loricariidae Hypopomus brevirostris x x 77 Hypoptopoma gulare x Sternopygus macrurus x Hypoptopoma inexpectatum x Otocinclus maculipinnis x Doradidae Otocinclus vittatus x Anadoras wedelli x x Loricaria simillima x x 137

Table 2. (Continued) dominated by the orders Cypriniformes, Siluri- formes, Gymnotiformes and Perciformes, the three former representing nearly 80 % of the three Loricariichthys maculata x x 2 hundred species occurring in the llanos. Ibarra Rhineloricariacf. parva * 1 and Stewart (1989) found in the Napo river basin Sturisoma robustum x in Ecuador, values of 51% for the Characoidei Hypostomus commersoni and 39% for the Siluroidei. Oliveros (1980) syn- Hypostomus plecostomus Pterygoplichthys anisitsi x15 thetized the composition of larger taxonomic Pterygoplichthys multiradiatus * groups in seventeen lakes related to the middle Parana river, which were, at the time of analysis, Belonidae separated from the rivers which fed them. This Potamorrhaphiseigenmanni fauna (85 species) comprised 55% Cyprini- Cyprinodontidae formes, 27 % Siluriformes, 11% Perciformes, 2 % Cynolebias bellotti x x 2 Atheriniformes, 2% Pleuronectiformes and 1% Neofundulus paraguayensis x x Rajiformes. Pterolebias longipinnis x x 30 Our values were comparable with the above Rivulus strigatus X X 2 mentioned ones as, the number of species in each Rivulus sp. order, related to the total number of species in the Synbranchidae area (136) was as follows: Cypriniformes 71 spp. Synbranchus marmoratus x x 14 (52.2%), Siluriformes 47 spp. (34.5%), Perci- formes 8 spp. (5.9%), Atheriniformes 6 spp. Cichlidae and Myliobatiformes, Synbranchiformes, Apistogramma borelli * 5 (4.4%), Apistogramma corumbae x x 4 Pleuronectiformes and Lepidosireniformes, with Batrachops semifasciatus x one species each (0.73%). Bujurquina vittata x x 65 In terms of number of species (number of spe- Cichlasomaportalegrense x x 250 cies by family and percentage of total considered Crenicichla lepidota X8 x species) the dominant families in our samples Crenicichla vittata Gymnogeophagus balzanii ~x x 1 were: Characidae 40 spp. (29.4%), Pimelodidae 17 spp. (12.5%), Loricariidae 12 spp. (8.8%), Achiridae Curimatidae 9 spp. (6.6%), Cichlidae 8 spp. Achirus jenynsi x (5.9%) and Serrasalmidae and Callichthyidae each with 7 spp. (5.1 %). Lepidosirenidae Lepidosiren paradoxa * 2 Distribution of new records

Table 2 lists all 136 fish species known from The eighteen newly recorded species (Listed in the Formosa province, showing those reported by Table 2) belong to the families Characidae Ringuelet et al. (1967a) (84 species), by Pignal- (6 spp.), Loricariidae (2 spp.) and Hemiodidae, beri de Hassan & Cordiviola de Yuan (1988) Curimatidae, Characidiidae, Auchenipteridae, (76 species) and by different authors after of, or Aspredinidae, Pimelodidae, Trichomycteridae, not considered in, Ringuelet et al. (1967a). The Cyprinidontidae, Cichlidae and Lepidosirenidae list also includes 89 species captured for this with one species each. The main characteristics of study, including 18 new reports for the considered their distributions are as follows. basins, and the number of specimens examined. Mago Leccia (1970) reported that in the '11- Aphyocharax nasutus anos' of Venezuela, as in other regions of South This species was described from the middle America, the water bodies have an ichthyofauna Parana in Rosario and subsequently reported 138 from the Paraguay river without precision basin. We obtained it at Loc. 1, 2, 4, 6, 7, 8, 9 (Ringuelet et al., 1967a; Ringuelet, 1975). Luling and 17 (EF) and Loc. 23, Western Formosa (1980) mentioned it from the middle Parana river (WF). and Cordiviola de Yuan et al. (1984) from near Santa Fe. We found it at Loc. 20 (Eastern For- Hyphessobrycon luetkeni mosa, EF). This species was mentioned as a bordering one by Ringuelet et al. (1967a), because it was known at Poptella paraguayensis that date from southern Brazil and the upper and According to Ringuelet et al. (1967a), this species middle Paraguay river in Paraguay. H. luetkeni was known from the La Plata and Paraguay riv- was found in the Riachuelo basin in Corrientes by ers, from the Matto Grosso state to Asuncion. Bonetto et al. (1978) (see Lopez et al., 1987) and Ringuelet (1975) reported it for the La Plata, from near the city of Santa Fe by Cordiviola de Parana and Paraguay rivers. A CECOAL (1977) Yuan etal. (1984) and Oliveros (1984). Lopez document showed it in the Yacireta area, and et al. (1984a) reported it for the first time from the since Luling (1980) it is repeatedly cited for the Uruguay river. There is a possible reference (the middle Parana river and related basins. Ramlow southern one) for the Buenos Aires province by (1989) reported it from the Tebicuary river in the Liling (1979). We found it at Locs. 1, 4, 6, 8 Misiones department of Paraguay. We found it at and 18 (EF). Loc. 9 (EF). Moenkhausia intermedia Astyanax f. fasciatus This species was first reported for Argentina Ringuelet et al. (1967a) reported this species in at San Lorenzo, Jujuy, as M. dichroura. It is Argentina for all the Paranoplatensean area, and known also from the Amazonas, Paraguay and its southern limit as the Salado river in the south- the upper Parana rivers, and from the Parana in ern Buenos Aires province. It is possible that Argentina (Ringuelet, 1975). In northeastern Ar- some references from this province really refer gentina it has been reported by Lilling (1980, 1982, to A. eigenmanniorum (Ringuelet etal., 1967a; Itati). Maldonado and Canon Veron (1983), Ringuelet, 1975), though there are recent refer- Miquelarena et al. (1980, Bella Vista) and Tab- ences by Ltlling (1979, Ing. Otamendi) and Lopez erner (1979, Riachuelo). We found it at Locs. 2, (1987, Laguna de Lobos). 7, 8 and 9 (EF). Menni et al. (1984), Haro et al. (1987, Rio II), Gutierrez et al. (1983, San Roque dam lake, Rio I) M. sanctaefilomenae report it from Cordoba, and Casciotta et al. In Argentina this species is known from the mid- (1989) from the Salado and Dulce rivers in San- dle Parana river (Lfiling, 1980; Oliveros, 1980), tiago del Estero. The far western references are by from the Riachuelo basin (Bonetto et al., 1978), Arratia etal. (1983, Jujuy), Lopez etal. (1984, from the Iberi (Bonetto etal., 1981) and the Tafi del Valle, Tucuman) (which provide detailed Yacireti area (CECOAL, 1977). Ramlow (1989) references) and Protogino (1987), who reported it reported it from the lower Paraguay river in Par- from El Nihuil dam (Mendoza). Miquelarena aguay. We found it at Locs. 4, 8 and 9 (EF). etal. (1990) found it in the Sali river basin in Tucuman. Beltzer and Oliveros (1987) reported Hemiodus orthonops A. fasciatus from the middle Parana, Bonetto et al. Miquelarena etal. (1981) reported this species (1981) from the Ibera 'lagoon', Fernandez Santos from the upper Parana river off Posadas Mis- et al. (1982) for El Palmar, Entre Rios province, iones, and cite previous references. It is men- and Quiroz etal. (1984) for the Salto Grande tioned from several localities in the Corrientes dam lake, in the Uruguay river. Ramlow (1989) province by Bonetto et al. (1978). Cordiviola de considered several localities in the Paraguay river Yuan & Pignalberi (1981) and Iriart et al. (1985), 139 and from the middle Parana by Oldani & Tablado ences. Mees (1974) indicated that it is widely dis- (1985). It is found in the Paraguay river (Ringue- tributed in tropical South America, and included let et al., 1967a), and Ramlow (1989) reported it Berg's (1895) references to its presence in Cata- from the neighborhood of Asuncion. We found it marca and San Nicolas environs. Arratia et al. at Loc. 2 (EF). (1983) also reported it for Catamarca, and Bonetto et al. (1967) and Iriart et al. (1985) for Cyphocharax spilota the middle Parana. Cordini (1977) and Sierra This species was formerly reported from Para- et al. (1977) mentioned it for the Uruguay river, guay. Miquelarena et al. (1990) report it for the and Ringuelet (1975) for the Paraguay river. Sali river basin in Tucuman under the name C cf. Ramlow (1989) reported it for several localities in modestus, suggesting that its identity must be con- Paraguay. We found it at Locs. 1, 5, 6, 8, 11, 13, firmed. Specimens with similar characteristics 14 and 20 (EF) and 23 (WF). were obtained at Locs. 1, 5, 6 and 7 (EF). Tridentopsis pearsoni Characidiumfasciatum fasciatum Described from Lake Rojoagua in Bolivia, this In Argentina Ringuelet et al. (1967a) and Ringue- species was mentioned for Argentina by Castello let (1975) reported this species for the Bermejo et al. (1978) from the Tragadero river in Ante- basin in Salta, the Sali basin in Tucuman, the quera, Chaco. Ramlow (1989) mentioned it from middle Parana (from where there are numerous the Paraguay river off Formosa, and from a Par- references) and from the middle Uruguay river. aguayan locality near the Pilcomayo river. We Ramlow (1989) reported it from the Confuso river, found it at Locs. 1, 4, 6, and 12 (EF). a Paraguay tributary, and other localities near Asunci6n. Gomez & Somay (1985) reported it Rineloricariaparva from Misiones, and Bonetto et al. (1981) from the Ringuelet et al. (1967a) and Ringuelet (1975) re- Iberi. There is an incidental reference to its pres- ported this species for Brazil, the Paraguay river ence in the Buenos Aires province (Escalante, and the middle Parana in Santa Fe, Argentina. 1984). We found it at Loc. 2 and 8 (EF). illing (1980) mentioned it for Corrientes. We found it at Loc. 9 (EF). Parauchenipteruscf. ceratophysus This species is known without precision from the Pterygoplichthys cf. multiradiatus La Plata, Parana and Amazonas rivers, and from Ringuelet et al. (1967a) quoted, with doubts, sev- Bolivia. We found it at Loc. 12 (EF). eral mentions of this species in Catamarca. We found it at Loc. 29 (WF). Dysichthys iheringi Ringuelet et al. (1967a) commented that no pre- Rivulus sp cise references were known of this species, though This still innominate species was described from it has been widely mentioned for the La Plata, the Bermejo river in Salta (Ringuelet et al., Parana and Paraguay rivers, also Rio Grande do 1967a). We found it at Loc. 26 (WF). Sul, Brazil, and Paraguay. Cordini (1977) reported it for the Uruguay river, and Lopez et al. Apistogramma borellii (1984a) for a tributary creek of the same. We Material examined by one of us (JRC), indicates found it at Locs. 6, 9 and 11 (EF). that this species is distributed along the Parana river and its tributaries in the provinces of Cor- Rhamdia cf. quelen rientes, Chaco and Santa Fe, and the Uruguay Though Ringuelet et al. (1967a) considered river in Corrientes. We found it at Locs. 4, 15 doubtful the localities assigned to this species in and 16 (EF). Argentina, there have been several later refer- 140

Lepidosiren paradoxa Table 3. Total number of species and specimens sampled by Ringuelet et al. (1967a) reported this species in the authors in Formosa environments. Argentina from the Bermejo river in Salta, the Locality Total number Total number neighborhoods of Resistencia, Chaco, the Para- number of species of specimens guay river in Asunci6n and the Iberf in Corri- entes. In 1975 Ringuelet reported it from the 1 17 610 Parana and Paraguay rivers and for the Bermejo 2 20 499 basin in Formosa and Salta. 3 5 5 Ramlow (1989) re- 4 19 148 ported it from the Pilcomayo. Though this species 5 17 293 is supposed to be widely distributed in North and 6 22 998 Northeastern Argentina (e.g. CECOAL, 1977, 7 23 145 Yacireti; Bonetto etal., 1978, Riachuelo basin, 8 28 174 and Neiff, 1981), 9 34 663 there was no concrete reference 10 6 8 for Formosa except for the imprecise one by 11 17 211 Ringuelet (1975). We found it at Locs. 15 (EF) 12 8 104 and 23 (WF). 13 8 67 14 4 242 15 5 5 16 8 45 Ecology 17 9 32 23 22 565 The total number of specimens collected was 24 2 2 4974, with a minimum of 2 at the locality 24 and 25 5 19 26 6 77 a maximum of 998 at locality 6 (Table 3). Per- 27 7 45 centages of individuals were 66% for characoids, 28 10 17 25% for siluriforms, and the remaining 10% for gymnotiforms, atheriniforms, synbranchiforms and lepidosirenids. These values differ somewhat with reduced size and shallow depth, extensive from those reported by Ibarra & Stewart (1989) plant cover and subjected to temporal level vari- for the Napo basin in Ecuador, where the chara- ations, explains the dominance of characoids, coids represented 82 %, siluriforms 15 % and eight cichlids and siluriforms of small size. Cordiviola other families the remaining 3 %. de Yuan et al. (1984) studied fish populations re- These situations differ from that in man-made lated to vegetation in environments associated ponds related to the La Plata river, where the with the Parana river providing a list of 58 spe- dominant species in number of individuals was cies, of which 44 are shared with our Formosa the clupeid Ramnogaster melanostoma limnoica, samples (a similarity of 76%). This explanations which is supposed typical in lenitic habitats, while is supported by the different composition of the R. m. melanostoma is riverine. fish fauna in larger water bodies such as Los In- In sixteen of the considered localities (1, 2, 4 to dios (14 ha) and Oca (120 ha) lakes, where in 9, 11, 13, 14, 16, 23, 25, 26 and 28) over 55% of number as in biomass a predominance was ob- the total capture in each environment was repre- served of'pacues', 'pirafias', (Serrasalmidae) and sented by at least four species. The most fre- pimelodids, usually of larger size than the species quently obtained were P. kennedyi, A. bimaculata, captured by us (Pignalberi de Hassan & Cordi- G. ternetzi, H. thoracatumand C. portalegrense.At viola de Yuan, 1988). Loc. 1 T. pearsoni represented 65% with The number of species in different localities 398 specimens forming a dense school collected ranged between 2 at Loc. 24 to 34 species at from the shore with a hand net. Loc. 9. Locality 24, where H. thoracatum and The predominant type of environment samples, H. littorale (both adapted to aerial respiration) 141 were captured, was a temporary pond 10 km away the Parana than that treated here is also poorer from the nearest aquatic environment. At locali- than the eastern one (Menni etal., 1984; Cas- ty 9, the Timbo Pora creek, captures were made ciotta et al., 1989). In spite of this, the situation in a cul-de-sac arm of the creek, 50 m length, is not simple, and some polymodal gradients can 4.20 m width and 1.5 m depth, perpendicular to probably be described if Uruguayan and Brazil- the main course. This had a strong current and ian sectors are considered, or if the main axes of deep water, which led to the supposition that this important rivers as the Salado, Dulce, and Sali environment functioned as a temporary refuge, are taken into account. Ringuelet (1975) was the explaining the high number of species. This could first to emphasize the existence of several gradi- also be explained by the separation of the arm ents of species richness, in spite of differences in and posterior evaporation. Similar situations have surface or other environmental characteristics. been reported for numerous environments related Among other examples, he stated that the 19 ha to the middle Parana. 'madrejon' Don Felipe (a separated arm of the During August 1986 diversity values ranged Parana river), had 54 species, while the southern- from 1.51 to 3.92, and during April 1988 between most 3000 ha Chascomus pond had only 21 spe- 0.71 (the minimum theoretical diversity) and 3.11. cies. Considering the Bermejo river basin, Ringue- Cordiviola de Yuan et al. (1984) studying fishes let (1975) stated that, from East to West, the Oca related to vegetation found a range from 1.25 to pond had 41 species, Luna Muerta in Salta 36 3.73. These values agree with those estimated by and the Lipeo river 14 species (See also Arratia Margalef (1974) for several fish taxocenoses. et al. 1983; Pignalberi de Hassan & Cordiviola de There is a marked reduction in the number of Yuan, 1988). species from the East to the West of the province: Fish richness in the studied environments, with 79 and 41 species respectively, with 31 species in the associated high values in particulate organic common. There were not differences, in spite of carbon and total P (for comparison with south- this, in the diversity values. No species of fami- ern environments see Water chemistry below), lies Gymnotidae, Hemiodidae, Characidiidae, strongly support Neiffs (1986) opinion about the Trichomycteridae, Lebiasinidae nor Aspredinidae ecological role of lenitic environments in the For- were obtained at the West. We suggest that the mosa area: the protective function of their vege- great richness in species in eastern localities is tation, their water storage capacity, control of due to the influence exerted by the Paraguay river flooding and drying periods, as nutrient traps, and the high number of environments related to and as high quality habitats for authochthonous the complex hydrography of the area (See Cas- and migrating wildlife. ciotta et al., 1989). The lower faunistic richness in western localities can be explained by the irregu- larity in the Pilcomayo river flow, which is scarce Water chemistry most of the year. However, historical factors can- not be disregarded, as the existence of impover- The parameters obtained (Table 4) are compared ishment gradients from East of West in some with our data from locations in Santiago del Es- zones has already been described (Ringuelet, tero (Casciotta etal., 1989) and Tucuman 1961, 1975; Arratia et al., 1983). The ecological (Miquelarena etal., 1990) placed SW of those characteristics of the considered environments studied here; with values provided by Golterman are also influential, including the size and dis- (1975) for the upper Parana and Paraguay rivers; tance to important water bodies or courses. This by Bonetto & Lancelle (1981) for the Parana; by is evidenced by a comparison between informa- Ringuelet et al. (1967b) for Pampasic ponds and tion from Pignalberi de Hassan & Cordiviola de by Lancelle et al. (1986) for environments in the Yuan (1988) quoted above with our data. The same eastern zone sampled by us. Other authors ichthyofauna from central Argentina, nearer to are referred to on particular points. 142

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Water field temperatures ranged from 17.2 to variable in the East (1.31-11.75, more than in 21 C (N= 12) in the East. Values of pH (6.14 to the Pampasic 'lagunas') but less variable in the 7.5) are similar to those observed in the Herra- West. dura pond, 40 km south of Formosa city, south The Mg + Ca/Na + K relationship gives mean of our eastern zone (6.6-6.8, Zalocar de Domitro- values of 0.77 in the East and 3.27 in the West. vic et al., 1982). They are lower than in Santiago This is related to low values of Ca in the East, del Estero (7.6-8.3) and Tucuman (7.5-8.78) or where this cation was not found in 33% of the than those from the Parana and Paraguay rivers. samples. For the same reason, the Mg/ These values agree with the lack of CO3 and the Ca quotient in the East reached 11.75, while in predominance of CO3H- waters (Table 4). Val- the West it ranged from 0.30 to 0.98. Concomi- ues between 6.4 and 8.6 were obtained by Pig- tantly, the water characterization according to nalberi de Hassan & Cordiviola de Yuan (1988) Maucha showed a predominance of the CO3 H - for 16 water bodies in eastern Formosa. Ca2+ type (5 samples) or SO Ca2 + type Dissolved solids values, alike in both areas, (1 samples ) in the West. In the East the predom- 1 ranged from 51.8 to 474.3 mg - , within the hy- inant type is CO3 H - Na + type (9 samples), as pohaline interval of Ringuelet et al. (1967b). These in the Paraguay river (Table 4), mainly hypocal- values, much higher than in the Paraguay river at cic. La Herradura (Bonetto etal., 1981), are lower Chemical oxygen demand (COD) (mg 02/1) in than those for Santiago del Estero and Tucuman, the East ranged from 24.5 to 39.5 (x=36.1). and well below those in the Pampasic 'lagunas'. These values are relatively high, being above those Conductivity ranged from 52 to 507 uS/cm, from the Paraguay river at La Herradura (2.3- being slightly lower in the East ( = 146.7) than in 11.2 mg 02 1-1), with the mean higher than in the West ( = 158.5). The maximum is higher than Chascomus. Obtained values are similar to those the 135 pS cm-' provided by Bonetto etal. reported by Lancelle etal. (1986) for the same (1981) for the Paraguay river at La Herradura. area in Formosa. Total phosphorus (mg P 1- ) These values are lower than those in Santiago del ranged between 0.079 and 0.760 ( = 0.450), val- Estero and Tucuman. Values in La Herradura ues similar to those reported by Lancelle et al. lagoon were from 65 to 310 iS cm- . Conduc- (1986) for the He-He creek (related with our lo- tivity values, compared with synoptic data cality 3), and higher than in Chascomus pond. It provided by Bonetto et al. (1981) appear rather is interesting to note that these high values of variable. As expected, they are more similar COD and P are associated with a rich fish fauna. to those obtained in the alluvial valley of the An opposite situation is given in the Ventana Parana river than those from the main course of highlands (38 ° 10' S). There COD values be- the river. tween 4.3 and 8.7 were obtained in creeks in Secchi disk values were similar to those from mountain landscape with an impoverished paran- the Parana river and environments in its valley. ensean fish fauna (Menni et al., 1988). Interme- Both pH and conductivity values are closer to diate values have been reported for the Pampean the Paraguay river than to the Parana, though ponds (Conzonno & Fernandez Cirelli, 1987), total anions + cations is higher than in the Para- which are intermediate also in geographic situa- guay river. tion and faunistic richness. Total anions in meq 1- ranged from 0.66 to Seston values (mgl-') ranged between 1 to 7.06 (somewhat higher in the East with a mean of 423 (x = 71.1), being similar or somewhat lower 2.28 against 2.06). These values are lower than than those obtained in pampean ponds by those in Santiago del Estero but higher than in the Conzonno and Claverie (1978) and Conzonno & upper Parana river or the Paraguay. Total cat- Fernandez Cirelli (1988). ions, with 0.64 to 8.44 meq 1- , show similar Values of particulate organic carbon (POC) (mg relationships. The Mg/Ca relationship is rather C -1 ) in Chascomus gave mean values of 7.9 and 144

6.85. Our samples ranged from 0 (3 locs.) to 15.4 ometas' o 'piranas' de las aguas del Parana medio. Acta (7 locs.) ( = 3.5, N= 10). zool. Lilloana 23: 45-65. Bonetto, A. A., D. Roldan & M. Canon Veron, 1981. Algunos Values of POC/seston, % ranged from 0 to aspectos estructurales y ecologicos de la ictiofauna del 17.9 (x = 5.2), somewhat lower than in Chasco- Sistema Ibera (Corrientes, Argentina). Ecosur 8: 79-89. mus. Bonetto, A. A., D. Roldan & M. Esteban Oliver, 1978. Estu- A detailed paper by Lancelle et al. (1986) is dios limnologicos en la cuenca del Riachuelo (Corrientes, dedicated to environments in the eastern area. Argentina). I. Poblaciones de peces en ambientes leniticos y loticos. Ecosur 5: 1-15. Values of parameters discussed here are rather Bonetto, C. A., A. A. Bonetto & Y. Zalocar, 1981. Contribu- similar to the values provided by those authors cion al conocimiento limnologico del rio Paraguay en su for the environments locally called 'esteros', dif- tramo inferior. Ecosur 8: 55-88. fering from those in creeks. This agrees with the Bucher, E. H., 1980. Ecologia de la fauna chaquena. Una mainly lenitic character of the environments sam- revision. Ecosur 7: 111-159. Burgos, J. J., 1970. El clima de la region Noroeste de la Re- pled by us. publica Argentina en relacion con la vegetacion natural y el suelo. Bol. Soc. Arg. Bot., XI (Supl.): 37-101. Cabrera, A. L., 1976. Regiones fitogeograficas argentinas. In Acknowledgements Encic. Arg. Agric. Jard., II: 1-85. Carter, G. S. & L. C. Beadle, 1930. The fauna of the swamps of the Paraguayan Chaco in relation to its environments. J. To Dr. Alicia Escalante and Dr. V. Conzonno for linn. Soc. London. Zool., 37: 205-258. criticism on limnological aspects. To Dr. R. Vari Casciotta, J. R., H. L. Lopez, R. C. Menni & A. M. for collaboration with the taxonomy of Curima- Miquelarena, 1989. The first fish fauna from the Salado tidae. To unknown reviewers for constructive river (Central Argentina, South America) with additions to criticism and patience with our English. To M. the Dulce river and limnological comments. Arch. Hydro- biol. 115: 603-612. Menni and C. Hertlein for computational facili- Castello, H. P., M. D. Erlich, I. R. Wais & A. Puig, 1978. ties. Adiciones a la fauna de los peces de los rios Parana medio y Bermejo. Rev. Mus. Arg. Cienc. Nat. Buenos Aires, Zool., XII: 119-135. References Cecoal, 1977. Estudios ecologicos en el area de Yacireta. Inf. de avance 2: 5-204. Conzonno, V. H. & E. Claverie, 1987/8. Phytoplankton pri- American Public Health Association, 1971. Standard methods for the examination of water and wastewater. 13th edn. mary production in Chascomus pond (Provincia de Buenos A.P.H.A. Ass., Washington. Aires, Argentina). Ecosur 14/15 (25/26) 7-16. Arratia, G., M. B. Penafort & S. Menu Marque, 1983. Peces Conzonno, V. H. & A. Fernandez Cirelli, 1988. Soluble humic de la region sureste de los Andes y sus probables relaciones substances from Chascomus pond (Argentina). Factors in- fluencing distribution and dynamics. biogeograficas actuales. Deserta 7: 48-107. Arch. Hydrobiol. 111: Azpelicueta, M. & L. Braga, 1980. Una nueva cita y ampli- 467-473. acion de la distribucion de dos especies para la ictiofauna Cordini, J. M., 1977. Temas relatives a la ictiofauna. Sem. argentina. Neotropica 26: 163-169. Med. Amb. y Represas. Univ. Rep. Fac. Hum. Cienc. Bayley, P. B., 1973. Studies on the migratory characin. Montevideo 1: 264-280. ProchilodusplatensisBerg, 1889 (Pisces, Characoidei), in the Cordiviola de Yuan, E., N. Oldani, O. Oliveros & C. Pignal- river Pilcomayo, South America. J. Fish. Biol. 5: 25-40. beri de Hassan, 1984. Aspectos limnologicos de ambientes Beltzer, A. H. & O. B. Oliveros, 1987. Alimentacion de los proximos a la ciudad de Santa Fe (Parana medio): Pobla- 'martin pescadores' (Ceryle torquata, Chloroceryle amazon y ciones de peces ligadas a la vegetacion. Neotropica 30: C. americana) en la lanura aluvial del rio Parana medio. 127-139. (Coraciiformes, Alcedinidae). Ecologia 8: 1-10. Cordiviola de Yuan, E. & C. Pignalberi, 1981. Fish popula- Berg, C., 1895. Sobre peces de agua dulce nuevos o poco tions in the Parana river. 2. Santa Fe and Corrientes area. conocidos de la republica Argentina. An. Mus. Nac. Bue- Hydrobiologia 77: 261-272. nos Aires, IV: 121-165. Chiozza, E. M. & Z. Gonzalez van Domselaar, 1958. Clima. Bonetto, A. A. & H. G. Lancelle, 1981. Calidad de las aguas In La Argentina Suma de Geografia, Peuser (ed.), Buenos Aires 2: 1-183. del rio Parana medio. Principales caracteristicas fisicas y quimicas. Com. Cient. Cecoal 11: 1-22. Drago, E., 1975. Mapa geomorfologico de la llanura del rio Bonetto, A. A., C. Pignalberi & E. Cordiviola, 1967. Las 'pal- Paraguay inferior. Revue Asoc. Geol. Arg. 30: 217-222. 145

Escalante, A. H., 1984. Contribucion al conocimiento de las Luling, K. H., 1980. Wissenschaftliche Ergebnisse des Fors- relaciones troficas de peces de agua dulce del area platense. chungsufenthaltes Dr. K. H. Luling in Argentinien 1975/76. IV. Dos especies de Cichlidae y miscelanea. Limnobios 2: II. Zoologische Beitrage, Neue Folge 26: 249-285. 562-578. Luling, K. H., 1982. Ein Verbreitungsgebiet von Apistogramma Fernandez Santos, J. O., I. R. Wais, A. Puig & R. Larrea, borelli liegt im Grossen Paranabogen. Aquarien Terrarien 1982. Observaciones sobre la ictiofauna del Parque Nacio- 29: 192-197. nal El Palmar. An. Parques Nac. 15: 77-105. Mago Leccia, F., 1970. Estudios preliminares sobre la eco- Golterman, H. L., 1975. Chemistry. In B. A. Whitton (ed.), logia de los peces de los llanos de Venezuela. Acta Biol. River Ecology. Blackwell Scient. Publ.: 39-80. Venez. 7: 71-102. Gomez, S. E. & D. E. Somay, 1985. La ictiofauna del Parque Maldonado, G. C. & M. B. Canon Veron, 1983. Notas sobre Nacional Iguazu y del arroyo Uruguai (Misiones, Argenti- la alimentacion de Moenkhausia intermedia Eigenmann, na). Res. XII Reunion Arg. Ecol., Puerto Iguazu, p, B23. 1908 (Pisces, Tetragonopteridae). Com. Cient. CECOAL, Gutierrez, M., M. J. Barla & L. M. Giraudo, 1983. Alimen- 14: 1-13. tacion de la poblacion costera de Astyanax eigenmanniorum Margalef, R., 1974. Ecologia. Omega (ed.), Barcelona, 951 pp. (Cope) (Pisces, Characiformes) del lago San Roque. Rev. Martinez, C. C. & S. M. Frutos, 1986. Fluctuacion temporal Univ. Nac. Rio Cuarto 3: 131-141. del zooplancton en arroyos y esteros del Chaco Oriental Haro, J. G., M. A. Bistoni & M. Gutierrez, 1987. Ictiofauna (Argentina). Ambiente Subtropical 1: 112-133. del Rio Segundo (Xanaes) (Cordoba, Argentina). Acad. Mees, G. F., 1974. The Auchenipteridae and Pimelodidae of Nac. Cienc. Cordoba, Misc. 77: 3-13. Suriname (Pisces, Nematognathi). Zool. Verhandelingen, Ibarra, M. & D. Stewart, 1989. Longitudinal zonation of 132: 1-256. sandy beach fishes in the Napo river basin, Eastern Ecua- Menni, R. C., H. L. Lopez & R. H. Aramburu, 1988. dor. Copeia 2: 364-381. Ictiofauna de Sierra de la Ventana y Chasico (Provincia Iriart, N. R., S. A. Massucchelli, L. A. Cavanna & J. Muniz de Buenos Aires, Argentina). Zoogeografia y paramet- Saavedra, 1985. Nuevos datos sobre peces de ambientes ros ambientales. An. Mus. Hist. Nat. Valparaiso 19: 75- loticos y leniticos del Parana medio, Argentina. Physis B, 84. 43: 31-38. Menni, R. C., H. L. Lopez, J. R. Casciotta & A.M. Lancelle, H. G., A. C. Longoni, A. O. Ramos & J. R. Cac- Miquelarena, 1984. Ictiologia de areas serranas de Cordoba eres, 1986. Caracterizacion fisico quimica de ambientes ac- y San Luis (Argentina). Biol. Acuat. 5: 3-63. uaticos permanentes y temporaries del Chaco Oriental. Miquelarena, A. M., R. H. Aramburu, R. C. Menni & H. L. Ambiente Subtropical 1: 73-91. Lopez, 1981. Nuevas localidades para peces de agua dulce Lopez, H. L., 1987. Apuntes ictiologicos de la laguna de Lobos de la Republica Argentina II. Limnobios 2: 127-135. (Prov. de Bs. As.). Bol. Asoc. Arg. Limnol. 5: 15-16. Miquelarena, A. M., R. C. Menni, H. L. Lopez & J. R. Cas- Lopez, H. L., J. R. Casciotta, A. M. Miquelarena & R. C. ciotta, 1980. Descripcion de Hyphessobrycon igneus sp. nov. Menni, 1984a. Nuevas localidades para peces de agua dulce (Characidae, Tetragonopterinae) y nuevas localidades para de la Argentina IV. Adiciones a la ictiofauna del rio Uru- peces de agua dulce de la Republica Argentina III. Neo- guay y algunos afluentes. Studies Neotrop. fauna and en- tropica 26: 237-245. vironment 19: 73-87. Miquelarena, A. M., R. C. Menni, H. L. Lopez & J. R. Cas- Lopez, H. L., R. C. Menni & A. M. Miquelarena, 1987. Lista ciotta, 1990. Ichthyological and limnological observations de los peces de agua dulce de la Republica Argentina. Bi- on the Sali river basin (Tucuman, Argentina). Ichthyol. ologia Acuatica 12: 1-50. Explor. Freshwaters 1: 269-276. Lopez, H. L., A. M. Miquelarena, R. C. Menni & J. R. Morgan, J. G., 1980. Los suelos de la provincia de Formosa. Casciotta, 1984b. Nuevas localidades para peces de agua Publ. Min. As. Agropec. Rec. Nat. Formosa, 47 pp. dulce de la Republica Argentina V. Historia Natural 4: Neiff, J. J., 1981. Panorama ecologico de los cuerpos de agua 81-90. del Nordeste Argentino. In Symposia, VI Jorn, Arg. Zool., Lopez, R. B., 1982. Migracion de peces en el rio Bermejo. II: 115-151. GAEA (Publ. Soc. Geol. Arg.) 15: 138-143. Neiff, J. J., 1986. Sinopsis ecologica y estado actual del Chaco Lopez, R. B. & H. P. Castello, 1966. Stemopygus macrurus oriental. Ambiente Subtropical 1: 5-35. (Bloch & Schneider) (Teleostomi, Sternopyginae). Primera Oldani, N. & A. Tablado, 1985. Dinamica temporal de pe- cita para la Argentina. Com. Mus. Arg. Cienc. Nat. Zool. quenos peces de agua libre en la laguna La Cuarentena (Isla 4: 13-16. Carbajal, Rio Parana medio). Studies Neotrop. fauna and Lowe McConnell, R. H., 1987. Ecological studies in tropical environment 20: 49-58. fish communities. Cambridge Tropical Biol. Ser., Cam- Oliveros, O. B., 1980. Campana limnologica 'Keratella I' en bridge Univ. Press, Cambridge. 382 pp. el Rio Parana medio: aspectos troficos de peces de ambi- Luling, K. H., 1979. Fische in temporaren und in Kleinge- entes leniticos. Ecologia 4: 115-126. wassern der Provinz Buenos Aires 2. Aquarien Terrarien Oliveros, O. B., 1984. Alimentacion de Hyphessobrycon 26: 245-249. luetkeni e Hyphessobrycon anisitsi (Pisces, Characidae) en la 146

laguna El Negro (Santa Fe). In Res. 11 Jorn. C. Nat. Lito- Ringuelet, R. A., R. H. Aramburu & A. Alonso de Aramburu, ral, Parana, pp. 57. 1967a. Los peces argentinos de agua dulce. Com. Inv. Cient. Palese de Torres, A., 1958. Hidrografia. In La Argentina Suma Prov. Buenos Aires, 602 pp. de Geografia, 2: 187-396 Peuser. Buenos Aires. Ringuelet, R. A., A. Salibian, E. Claverie & S. Ilhero, 1967b, Pignalberi de Hassan, C. & E. Cordiviola de Yuan, 1988. Fish Limnologia quimica de las lagunas pampasicas (Prov. Bue- populations in the Paraguay river waters of Formosa area, nos Aires). Physis 27: 201-221. Argentina. Studies Neotrop. fauna and environment, 23: Shannon, C. E. & W. Weaver, 1963. The mathematical 165-175 theory of communication. univ. Illinois Press, Urbana, Protogino, L. C., 1987, Presencia de Astyanax fasciatus y 177 pp. Astyanax abramis (Pisces, Characidae) en el embalse El Sierra, B., H. Osorio, A. Languth, J. Soriano, E. Maciel, O. Nihuil, Mendoza, Argentina. Limnobios (2-9): 676. Mora, R. Ayup, A. Lombardo, E. Palerm, J. Gonzalez & Ramlow, J. M., 1989. Lista de peces y sitios de coleccion de F. Achaval, 1977. Ecosistemas afectados por la construc- la seccion de ictiologia del Inventario Biologico Nacional cion de la represa de Salto Grande. Semin. Medio Amb. y Museo Nacional de Historia Natural del Paraguay (Junio Represas, Univ. Rep. Fac. Hum. y Cienc., Montevideo 1: 1980-Diciembre 1988). Bol. Inv. Biol. Nac. Paraguay 9: 89-130. 1-40. Siragusa, A., 1975. Lagos, lagunas y salinas. GAEA, 7 (2da. Ringuelet, R. A., 1961. Rasgos fundamentales de la zoo- parte): 571-625. geografia de la Argentina. Physis 22: 151-170. Taberner, R., 1979. Datos para el reconocimiento biologico Ringuelet, R. A., 1962. Ecologia acuatica continental. Eudeba, de Paracymothoaparva Taberner, 1976 e Isonebula maculata 137 pp. Taberner, 1977 (Crustacea, Isopoda, Cymothoidae). Rev. Ringuelet, R. A., 1975. Zoogeografia y ecologia de los peces Mus. Arg. Cienc. Nat. Buenos Aires, Parasit., 2: 77-86. de aguas continentales de la Argentina y consideraciones Zalocar de Domitrovic, Y., C. A. Bonetto & H. G. Lancelle, sobre las areas ictiologicas de America del Sur. Ecosur 2: 1982. Algunos aspectos limnologicos de la laguna La Her- 1-151. radura (Formosa, Argentina). Ecosur 9: 171-188.