DISTRIBUTION OF THE FISHES 61 TABLE III.—Conceluded = i S bs ‘ ox a] e he SoS calms Bier ele |= | a| o BS) 82) 5 o |F | SOS ett oes sel=a| a r= s ° s ae VE cs a] 3) £ = at ee Bee TS Sel Ss |ha| & SR ee R= i eee le = rai) 1S z ye | HN I CS I = leele|2| = |sé|z 28/82) 3 eo 12a) & ° o S Helge} 2 2S) ise A SS ae SSeS eee ea = ane) a tse ilies Sig le o Orestias agassizil. . . fo ee Bera cee | eereest SCI Om, Mk coa all x< =~ empyraeus:. =: ‘ Space | feeea cel | teRealll aces co) h Neh tea eae alle atk “ miilleri. SR a aid alee Glin ae Ser ata eee salle eka|| ball OM silustani. we eh: cUctee eee x CF Out, | 6 sese Bs ced tap age Se een |e le a epee even epee ale ecPa sally 2: 7.1 |" OX SEE LOSDICLOSInee eee er eT Seeley alles ofall welled tn eee ene Ay x Bote USSICT. 6, oe asian MOEA eet eal eiber ene | selcims lease oer. eee Se tSChi Giese Ct yn Selah ae Bell eee plus ce sl heart a Ae S|} ps =) humboldtre 5 5 Re ells See eaeed eee Belle Ba voll te ea Leet Pho aells ee x * pentlandis.. at re eH ol es St Be otreeea (Coss len Corer] eres | ene ee x Go Gidea sesnoone : Pete SE TEA Pesaro Rec ere scarce a cal eaee erste x ee LUCUS ese siete ee Ile Erol rotera le aicne eee eral ee x smmera lbUSz ae Ao.4 : Se egrets leaevenal ere oe ees | eee Sef eats news eke ca hook 45.OMKURKAAUIS:,65meoopnererBSeaseleaeealTeas[oerSees|eesoeeeencealleee(eeeos[eectx = PINCAC RH enc ee Pes ase lieder |eenal [ones Meena neal ete [Glen Saal ty emilee ls Tylosurusamazonicus......WeoddstateGeekeredGrallacalleeyed]aeraano<aPnarea[arsae anne ZEquidens tetramerus | . een ne Re Ea ew peel ll eae x Crenicichla saxatilis. . . eee Ee es (oes lene re [eae ATED ea ces 8 IS oa fe ea . IWCIUS eee exe Een eat eee |e 2 | a dra NN Sa tl ina eo | ee eee al a(XWAlossdaaeOarspeckcastletallhoc=[beenlbeccadisasterasseehg Species italicized in Table III are from unique localities; Hemibrycon helleri doubtfully identical; Astroblepus praeliorum from streams arising in the same area. DISCUSSION The evidences and the conclusions concerning distribution in other regions of South America are discussed by Eigenmann (1909, 1912, 1922, ete.) Since so large a part of the freshwater fauna of the continent belongs to only a few families several of which are represented also in Africa, and since certain Geological facts lend support to the theory, he considered the demonstration sufficiently complete that the fishes of South America have their nearest kinship with those of the Eastern Hemisphere. Whether an Archhelenis-Archiplata continent existed all at one time or piecemeal, a freshwater communication with Africa appeared to be the most logical explanation of the facts. Rejection of the theory seems to permit only one alternative, the much broader assumption of many cases of close parallelism, purely fortuitous, between the fishes of the two continents.
The present discussion has to do with the youngest major portion of South America, antedated through long geological periods by the freshwater areas of Brazil and the Guianas. Regardless of the earliest beginnings of the ichthyfauna, the migration routes into this area from the older streams are discernible (Higen-
62 FISHES OF WESTERN SOUTH AMERICA mann, 1922b, d; 1923a). Although most of the stocks passed through periods in which they inhabited the eastern highlands, it was not until the Amazon developed its great freshwater basin that it became the greatest hatchery of species known. From there Haseman (1912), Pearson (1937b) have traced the highways of dispersal in various directions, while Eigenmann, |. ¢., found that the fishes of the Pacific slopes had to traverse a circuitous route around the low northern Andes of Colombia to reach their present habitats.
Pearson finds two major sources of the population of the Paraguay, the Guaporé, and of the Bolivian headwaters of the Madeira, the latter more nearly resembling the upper Amazonian fauna. Our fishes from the upper Peruvian Amazon and its tributaries should therefore exhibit close kinship with those of Bolivia, and they do. This is true, not only for the lowland species, but we find a number of fishes such as the Hemibrycons inhabiting regions of intermediate elevation in the tropical rain forests of both Peru and Bolivia. In Peru as in Bolivia and La Plata, the changes in a fauna as we proceed from the Amazon southward are similar, that is, changes mostly by subtraction. None of these facts aid in explaining the origins of the respective families, nor do we find any facts which would support Haseman’s theory as to a North American origin of Characin fishes. The present study differs from those previously made: in the age of the formations which determine the types of habitat; in the large-scale topographic relief; and in the length of the period of occupancy. Like most of the continent, it is part of a unit uncontaminated from north, west, or south, and having its only family ties with the East. Numerous families are of tropical South American origin, and are confined to that continent, such as: Loricaridae, Astroblepidae, Callichthyidae, Aspredinidae, Hypophthalmidae, Pygidiidae, Gymnotidae; also numerous characin subfamilies.
The fauna has developed with the continent itself, and despite the youthfulness of our region, sufficient time has elapsed to differentiate the Pacific slope fishes completely from those of the Atlantic side, at least to species, and sometimes to distinct genera.
The upthrust of the Andes as described above has created barriers more rapidly than weathering processes could smooth them down. This has resulted in the creation of: (a) the land-locked Titicaca-Poop6 basin, and of numerous areas, large and small, throughout our area, having mature topography and high elevation, plains, lakes, marshes; (b) a second, subtropical, zone to which some of the inhabitants of the first zone have escaped; (c) a zone of still lower elevation to which certain genera of Amazonian fishes have been able to ascend; and (d) the tropical lowlands, richly and abundantly populated from the various centers of dispersal of the Amazon system.
The first and most elevated zone is occupied almost exclusively by fishes descended from those which were elevated with the mountains themselves. The second zone consists of limited localities with suitable terrain to encourage the further evolution of highland fishes, such as the Astroblepus of southern Ecuador. The third zone whose extent is to be described below is marked off from those above by greater or less extent of rapids, and represents the farthest reach of a
DISTRIBUTION OF THE FISHES 63 few scattered pioneer types from the lowland. The fourth zone presents, apparently, the limitless waters of the tropical lowlands, with its opportunities for an ageressive or resourceful species. To this zone belong the greater part of the characin and catfish faunas, which have responded to the opportunity in an unparalleled way. Events have transpired in such a way as to permit not a few marine or estuarine fishes to become readjusted to the fresh waters of the new habitats, so that the uppermost Amazon remote from the sea has its stingrays, its flatfishes, puffers, anchovies, ete., as well as its otter, porpoises, and manatees. At Cayumba rapids, 8000 miles from the ocean, even a crab was found, elevation 1800.feet.
Table II shows at least qualitatively the degrees of relationship between our area and other major systems. Unique species are not given, not being of value for comparison. As should be expected most, 201, of the lowland fishes given in the table belong to the Brazilian Amazon also. The entire Amazon isa unit from its mouth to the point where it was an inland sea washing the foothills of the Andes. One-hundred ten, less than half the 246 lowland Peruvian species, have also surmounted the low barriers of the upper Madeira to the Beni, Mamoré, and Paraguay. Pearson, 1937b, in a total of 485 species from Bolivia (including also mountain species and uniques) finds 316 common to the Paraguay, 229 found in the Amazon. The Guiana fauna has no less than 97 species reaching the lowlands of Peru, indicating a not very remote separation biologically. There is little doubt that the 68 species mutual to lowland Peru and Venezuela or westward show only the lack of exploration of the farther reaches of the Orinoco.
The streams of the Atlantic seaboard are short and disconnected, and he on the farther slopes of the Brazilian plateau, and our table lists only some 26 of their species in the lowlands of Peru.
The fishes of the highlands are almost wholly distinct from those of other regions. The intent of Table III is, therefore, not to make comparisons with outside areas, but to analyze the distribution within the region itself. Uniques are included.
The Maranon and Santiago boast the largest number of known species, 34, in elevations mostly 3000-4000 feet. It will be noted that most of them are either lowland species or closely allied to them, obviously derived from the Amazon fauna, which has met with considerable success in passing barriers formerly considered impassible. The greatest obstacle to passage upstream is to be met at the point of emergence from the intercordilleran valley upon the Amazonian plain, the watergap known as the Pongo de Manseriche. When I visited it, I was informed that a number of steam launches had succeeded in ascending the rapids, while the books tell of numbers of canoe-parties making their way through the pongo safely. It has therefore not constituted a very formidable barrier to lowland fishes. The larger Pimelodus-types, flying-fishes, piraruci, and fishes of great size, quiet waters, marshy habitats, etc., have not made the ascent. The smaller, intrusive or sucking-mouthed types, and mountain types of Characin, such as Hemibrycon, have done better, including two Gymnotids.
The Pichis river is a good example of a lowland stream deeply invading the
64 FISHES OF WESTERN SOUTH AMERICA highlands, and certain other lowland fishes have readily made their way there, such as Bario or Tetragonopterus argenteus. Ease of access has made it equally desirable to fishes and to the canoes and launches of the Via Central. The Tarma-Chanchomayo-Perené drainage is one with numerous rapids and much difficulty of ascent; thirteen species were taken, nine of them lowland forms. The middle Huallaga has been represented by such small and casual collections that we might be misled into believing that few aggressive lowland forms have populated it from below; probably many more will be found than the ten listed from R. Huambo and R. de Totora. Juan Mesa, a riverman, was able to name for me offhand more than twenty which he had known at Tingo Maria at the mouth of the Monzon. My collecting in the troubled waters of the Upper Huallaga (from Cayumba rapids at 2000 feet to 14000 feet) and Dr. Eigenmann’s collections in the sources of its tributary, the R. Yanahuana produced a total of thirteen species. The Cascada de Cayumba I found to be a much more precipitous hazard than the Pongo de Manseriche, and, I believe, satisfactorily accounts for our total of only thirteen species above it, as against 34 of the Alto Maranon. The middle Urubamba is guarded from the invasion of lowland fishes by the formidable Pongo de Mainique, which I did not visit. (Bowman, 1916.) Yet it is far from being fish-proof, since 22 species have been recovered from the river above this point, 15 of which should be classed as lowland forms, seven from the upper reaches of the river and its tributaries. From the number of lowland forms it should be rated between the Maranon and the Huallaga as to ease of invasion. It must also be remembered that the headwaters of the Urubamba and those of the Maranon are at about the same elevation, but that the former has about twice the distance in which to climb a stair of equal height. Except for extreme barriers, the longer streams should have the more abundant fauna. Unfortunately the records from the Apurimac, which should give light on this point, are very scanty. Our collections show that only the genera Orestias, Pygidium, Astroblepus, with some Chaetostoma, belong to the fauna of the high Andes. The center of dispersal of Astroblepus appears to be in the lower elevations of the Andes of Southern Ecuador, diminishing in species southward. Pygidium centers farther south, some 26 species having been collected north of our area, some 39 southward, most of them following the crests of the ranges.
Aside from the climbers mentioned above, we have the same types of Characins recurring in the Urubamba as in the North, such as the Astyanax-Hemibrycon- Bryconamericus group, and the same Apteronotus and Sternopygus. Most of the remainder are uniques.
The Titicaca basin has produced most of the Orestias. Except for the two which have arisen in central Peru (Province E) and three in the upper Urubamba valley, the genus is still limited to that basin.
Orestias is the only clear-cut endemic genus of the upland pampas of the Andes; Astroblepus is probably so, but has representatives well down toward sealevel. There is more doubt about the widely dispersed Pygidium. While Othonocheirodus, our Hemibrycon, Ceratobranchia, Bryconamericus, and Creagrutus are
DISTRIBUTION OF THE FISHES 65 spoken of as mountain genera, they pertain to the fauna of the rapid rivers of the tropical rain forest, elevations of a few hundred feet to 5000 or 6000. Prior to the National Geographic Society’s collections and our own the following fishes had been listed from the upper and Middle Urubamba: Hypostomus bufonius and calamita by Cuvier and Valenciennes Astroblepus sabalo - et vi Pygidium incae gracilis Orestiasowenit ue eUUSSVED agassizi1 pentlandi fuscus Astroblepussabalo Pygidium dispar Acrobrycon ipanquianus ce Garman Cope a3 “ is The distribution of the mountain fishes by genera rather than by species may be more graphic and illuminating:
Astroblepus Andes Urubamba to Panama and Mérida 3800-13400 feet Ancistrus Rio Chagres to Guiana and Buenos Aires up to 9000 feet Pygidium mountains Punta Arenas to Panama 0—-14000 feet Pimelodella Panama to Buenos Aires 0—6000 feet Bryconamericus Costa Rica to Buenos Aires 0—4000 feet Acrobrycon Eastern slopes Bolivia, Peru 4000-8000 feet Hemibrycon Urubamba to Panama and Trinidad 0-11500 feet Creagrutus s “i = * Guianas 0-4000 feet Ceratobranchia Southern Peru to Chanchomayo 2000-3500 feet Astyanax Texas to Buenos Aires 0—3500 feet Orestias Mantaro to northern Chile 9000-15000 feet Steinmann (as quoted in Eigenmann, 1909, III, 372) holds that as late as the Tertiary the Titicaca basin was a body of water or a deep valley draining normally southeastward to the southern tributaries of the Amazon. The rapid rise of the Eastern Cordillera interrupted its outlet, creating its closed system of drainage. Looking at the topography from the pampa above the La Paz gorge, you would be inclined to take that view of it, although an equally alluring solution is presented south of Uyuni by the intercordilleran valley now closed by volcanic action. For the following reasons I should prefer to regard the Titicaca basin as a closed one for a much longer period.
Prior to the extreme present elevation of the Eastern Cordillera the interior valley should have had much greater rainfall, as the lower eastern ranges of the time would have been less effectual in cutting off the southeastern trade-winds. If an open way to the Atlantic existed then along the path of the moisture-laden winds, it would have been kept open. Northward of this, the present valleys of the Urubamba, Apurimac, etc., have maintained an outlet despite the rise of high
66 FISHES OF WESTERN SOUTH AMERICA ranges eastward and the creation of large areas having a dry climate at their headwaters.
The existence of terraces showing that Lake Titicaca was once much larger, extending as far as Pueard, and that the Desaguadero is paralleled by the shorelines of an ancient strait, were pointed out by Agassiz in 1875 (q. v.).. The present shrunken lake is evidence of a progressively drier climate with the upthrust of the Bolivian cordillera. That it has been in more or less continuous existence from the date of its rise from the sea is indicated by the considerable saline deposits on the land, and the brackish character of the waters of Lake Poopé. The terraces 300-400 feet above the lake are much higher than the present pampa which holds back the exit of the lake through the Rio La Paz. This goes to show that when they were formed the La Paz area was much higher, and that the cutting down of the La Paz gorge through the soft, alluvial formations is of subsequent occurrence. The fishes of the lake gained admittance to this closed system from the parent sea itself, rather than via an Amazonian tributary, and their lack of kinship with other fishes of the continent would lead to the same conclusion.
In the above paper Eigenmann says that while isolation is a necessary condition to species-formation, there is insufficient isolation in Lake Titicaca itself to have given rise to so many species. That has been one of the puzzling questions in the present study. We find perhaps the most complete, if not the longest, isolation to be that of Lake Ascotan, Chile, yet, except for color, its fishes differ little from those of the great lake. On the other hand, the nearby Lake Umayo, rather well separated, has been prolific of species not yet found in the greater, parent body. Furthermore, our collecting records show that there is an assortment of species with depth, and between the lake and its tributary streams, the nearest thing to isolation I can suggest. But, here as elsewhere, we do not often find more than one or two species in any particular locality.
For a long time I was troubled to answer the question as to the distribution of Orestias agassizi, supposedly existing all the way from the Nudo de Pasco in the north to Lake Ascotan a thousand miles to the south in the Chilean Andes, connected by a terrain dissected to a depth of many thousand feet by the Mantaro, Apurimac, and Urubamba, an effective barrier except perhaps about the high passes of the voleanic western cordillera. How could a species maintain its integrity against such odds? There seemed to be a tentative answer in our finding the species even at the extreme elevation of 14660 feet in the pass Crucero Alto. But now after a careful restudy of all my specimens and comparison with those from the California Academy of Sciences, I find that the species are distinct in central and southern Peru. The confusion arises from the close resemblance of the immature stages, for the adults are quite unlike. We may look to the Crustacea for additional evidence of the marine origin of Lake Titicaca, for seven species of Orchestiids exist there.
Resumé: In the total absence of species derived from southern invaders, only Astroblepus from the northward, no Pacific slope forms scaling the extreme heights, we have only two primary sources of the fishes of the cordilleras and interandine valleys. These are the aggressive species from the Amazon and the endemic upland forms.
ICHTHYOLOGICAL GAZETTEER The recently completed sheets of the American Geographical Society’s Millionth Map are in the more settled areas a very good source of information as to the terrain and places. The “Mapa General del Peru’’, published by Carlos Fabbri, Lima, is especially good on the current usages In naming streams in Peru. South American geographical nomenclature has suffered from the not uncommon evils of ambiguity, fashion, indefiniteness, and translation. The Peruvian often says to the traveler, ‘Oh yes, you are from the United States.—From New York?” Conversely collectors not infrequently record their specimens as from South America, or Brazil, or the Ucayali.
Some of the practical difficulties which I have experienced in interpreting locality records will be of no less interest to others, and the following is a more or less complete statement of them.
(1) The name of the nearest large town or village is used. E. g. Iquitos for all Loreto; or Quito for the entire hinterland of Ecuador. (2) The names of private estates, sometimes duplicated in various regions, with no explanation from the collector, and subject to the caprices of future owners in changing names.
(3) Similar duplications in the names of streams, such as four tributaries of the Huallaga named Cachiyacu; or Rio Grande, Rio Colorado, ete., so often repeated.
(4) Names used interchangeably, sometimes Indian and Spanish, such as Poopé and Aullagas, or Junin and Chinchaycocha.
(5) Name changing with political power. Puerto Pardo on the Morona was Puerto Leguia when I visited it, and is again Puerto Pardo today. Punta Arenas became Magallanes, then reverted as before.
(6) Confusion of spelling: the use of Gu or Hu, J or X, B or V, Y or Ll, mayo or mayu, yaco or yacu; various renderings into other languages of local names; lack of standardization of spelling, the distinguished geographer Raimondi no less than others spelling the same words in a variety of ways. (7) Confusion in the extent of a stream under the same name. Often when two streams converge, not one, but both names are exchanged for a third. E. g. the Chanchomayo and Paucartambo unite as the Perené.
(8) The removal of a town to a new location, on account of a railroad (as Challapata), the encroachments of a river (Contamana).
(9) Compounded names, such as San Juan de la Frontera de los Chachapoyos. The following list of place names concerned with ichthyological collections and locality records is an attempt at identifying and stabilizing them. The symbols used are as follows:
*Collections made by Allen; **Collections made by Eigenmann; ***Collections made by others and studied by us.
67
aio") FISHES OF WESTERN SOUTH AMERICA Names without symbols are places from which we have seen no specimens. In a few instances names are included although no specimens were obtained, when the regions named were vainly explored and it is certain fishes do not occur, such as Oruro.
Acora: village inland from Chucuito, near L. Titicaca and Puno bay, on Camino Real, the ancient road from Bolivia (Upper Peru) and Puno to the capital city of Cuzco; a flat pampa country with poorly drained ditches; elevation 12600 feet.* AGUACHINI: small river on the Via Central, emptying into the Pichis near Puerto Yessup; usually a clear mountain stream, fordable; during freshets must be ferried by raft.* AGuas CALIENTES: many warm or hot springs go by the name. In particular, (1) near sources of Rio Poopé, Bolivia,* inland from the village of Poopé; (2) warm, boggy springs in the La Raya pass,* and forming the source of the Rio Vileanota; others nearby on the other side of the pass, at the headwaters of streams forming the northern extremity of Titicaca basin.
AMABLE MarIA: presumably an estate, on or about the middle course of Rio Tulumayo, eastern-central Peru.
AMAZON, AMAZONS, AMAZONAS: (1) upper Maranon, Alto Maranon, Intercordilleran Maranon, from the source at some 16000 feet elevation on the knot uniting the western and central Cordilleras down to Lago Lauricocha and the gorge of the Maranon, bending abruptly eastward and escaping to the Amazonian plain at the Pongo de Manseriche (q.v.).*** Its largest tributary the Rio Santiago. (2) Alto Maranon; this name applied also to that portion of the river from the Pongo de Manseriche to the mouth of the Ucayali.* (3) Bajo Maranon; from the junction of the Alto Maranon with the Ucayali to the Brazilian border.* (4) Peruvian Amazon or Amazons; includes all three of the above sections.* (5) Solimodes; from the Peruvian border to the mouth of the Rio Negro (others say the mouth of the nearby Rio Madeira). The Brazilians insist that the Amazon as such heads at this point, although it continues in a very direct line for some 1500 miles further upstream.*** (6) Amazon; lower Amazon, bajo Amazon; from the mouth of the Rio Negro to the sea, in the Brazilian sense. In the broader sense, all the four sections namedabove.*** The northern Peruvians claim the name for the entire river. The southern Peruvians hold out for a nomenclature which would establish the sources of the Amazon at the head of the Rio Apurimac in southwestern Peru, since it, together with the Ucayali, constitutes the longest course. Apo: village on western bank of the upper Huallaga, some fifteen miles above Hudnuco, and at the junction of the Rio Huacar (Yanahuanca). Marks the most elevated point where fishes were obtained on the Huallaga, at near 7000 feet elevation.* Ampyiacu, Rro: small, lowland stream entering the Peruvian Amazon from