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 Grigri writes "A paper By Juan Miguel Artigas.
Many thanks to kindly allow us to publish it on Goodeids.com
All you want to know about the last Characodon populations... from a survey made by the author in all the Characodon sites.
Introduction
Back at the beginning of the 20th century the dry lands of the Guadiana valley in the northern Mexican state of Durango were the home land of one of the most brilliant, bloody and infamous of Mexican revolutionaries, better know as Pancho Villa, although his original name was Doroteo Arango. He was famous among many other things because in 1916 he led the only army, the ”northern division,” that has ever invaded the Continental United States. This happened after the US government had decided on supporting his enemies in México city. The ancient volcanic lands of astonishing beauty are famous also for the deadly scorpions that inhabit them, and their romantic landscapes were a preferred set for the making of popular western movies.
Silent witnesses of this land’s history for countless years, a small group of desert fishes has managed to survive the many tests that nature has put on them for their survival, battles that after thousands of years of winning they have just started to dramatically lose to human population expansion, ignorance, lack of love for nature and greed.
Isolated in some of the most incredibly small and vulnerable habitats known, the species and populations of the ancient livebearer cyprinodontiform genus Characodon are desperately calling for the attention of those that among their enemies have the virtues that could save the species from their total extirpation from this universe, a rescue that unfortunately does not seem very likely to happen.
The whole family Goodeidae comprises what may eventually end up in a little over 40 species of fish, all endemic to the western part of central México and a separated area in the Southwestern United States. This interesting and unique group of both livebearing and egg-laying fishes has seemingly evolved from the egg laying cyprinodontiforms of the genus Profundulus (Webb, 1998) that inhabit the mountain streams in the southern part of México and Central America. Their diversification has involved vicariance (isolation due to natural processes, which can eventually lead to speciation) owing to geologic activity along the Neovolcanic ridge of México. This chain of volcanoes divides México horizontally, and has no doubt caused the piracy of tributaries and the isolation of basins. The result is a geographical area full of astonishingly beautiful features, including volcanoes, forests, ridges, lakes, mountain creeks and rivers, among others.
General description
Characodon are small fishes no bigger than five centimeters in males, with females reaching just a little bit more. Their coloration has been partly the cause why many aquarists readily fall in love with them. Males and females are dimorphic in body patterns, the males being those with the nicer colors. Males normally show unpaired fins of striking coloration, mostly black or red with a black margin. The scales on the flanks, with more intensity on those in the rear-half of the body, show a beautiful iridescence in silver, green or blue, depending on the population origin, which forms a reticulated pattern on a dark colored background. Males also show a ventral yellow to orange color in the lower area of the head, in the throat and the rear part of the pectoral fins. Characodon have a dark back. Females, less colored than males, are normally olive green to gray with some degree of yellow coloration on the body. They have translucent fins and an arrangement of black blotches along the mid-lateral flanks, present in some populations.
In external appearance, Characodon are fish with very robust and moderately compressed bodies, small pelvic fins set back in the body, around the middle part of it. The dorsal fin has a short base and is located far back in the body, its beginning closely matching that of the anal fin or even a little behind.
Characodon belong in the livebearing sub-family Goodeinae of the family Goodeidae. The first few (of eight) anal spines in males are shorter in size and form the andropodium. This organ has been described as a gonopodium (Turner, Mendoza, and Reiter, 1962), the modification of the first few anal fin rays of the Poeciilid males to transport sperm to the females. Apparently, the andropodium is only a ”physical clasping appendage” common among viviparous halfbeaks (Hemirhamphidae) and some South American killifishes to hold the female proximal to the male, while a muscular intromittent organ is extruded from the male’s urogenital pore. Although the existence of such a muscular organ in male Goodeines has been proven (Mohsen, 1961a, 1961b), its function has not. So, it is probably this organ and not the andropodium that accomplishes insemination. The andropodium divides the anal fin, giving rise to the common name for the Goodeines of ”Splitfins”.
Male Goodeines have a little longer dorsal and anal fins with more rays on them. The caudal fin is rounded. Characodon normally have a pointed head with some indentation above the eye in some populations, holding small mouths facing upwards.
The trophotaeniae, which are the equivalent of an umbilical cord used by Goodeines to feed their pre-born babies, are particularly shaped in Characodon, having just two elongated un-branched processes joined at the proximal end.
Taxonomy
Characodon was described as a genus in 1866 by Albert Günther, the legendary fish curator of the British Museum of Natural History. The generic name is probably inspired by the sharp bi-cuspid row of teeth in the middle part of the fish's jaws, in Greek, "odus" is a tooth and "characo" means "notched or cut in", "charax" refers to a pointed stake. Günther considered Characodon monotypic (comprised of only one species) and described C. lateralis as the type (and only) species. Günther based his work on specimens that were stated to be collected by Dr. Seeman's in southern Central America, an error in locality later recognized by subsequent researchers. Leonard Michael Smith and Robert Rush Miller (Smith and Miller, 1986) recognized that their material for C. lateralis, collected in upper Rio Mezquital in the state of Durango, corresponded to the same species that Günther used in his description in 1866.
In the same paper, Smith and Miller set the current status of the genus Characodon by describing a then recently discovered species of Characodon from the isolated spring of ”El Baño de las mujeres” near the town of El Toboso in the valley of Guadiana; C. audax, specific name referring to the aggressive intraspecific disposition of males of the new species. The holotype for C. audax was collected by a party including Robert and Frances Miller in 1982.
Smith and Miller also recognized the validity of the formerly described and now extinct species C. garmani Jordan & Everman 1898, that had been relegated to synonymy of C. lateralis by Tate Regan (Regan 1906-1908), curator of fish at the British Museum of Natural History (after Albert Günther). C. garmani, which we just know by one female (MCZ 27704), honors the ichthyologist Garman, who had recognized the differences of the female from C. lateralis as he examined a collection of fishes made by Edward Palmer in a spring or stream near the city of Parras, Coahuila, several hundred kilometers northeast from the Valley of Guadiana, in the Chihuahua desert.
Origin
Characodon are genetically distinct from other goodeid genera (Fitzsimons, 1972) and thought to be the most primitive members of the goodeid subfamily Goodeinae (Webb, 1998). Characodon branches evolutionarily from the very base of the sub-family, putting it apart from the rest of the Goodeinae genera. The Characodon genus is restricted to the valley of Guadiana, a small area in the state of Durango around the capitol city, and was also known in a discontinued population east from Durango in the Coahuila valley of Parras. Characodon seems to be, and their external appearance testifies so, the closest relatives of their now far away disjointedly inhabiting cousins of the sub-family Empetrichthyinae, the other Goodeid sub-family that is comprised by four species restricted to a small area in the dry southwestern United States, in the state of Nevada.
It seems that back in history Characodon and those species in Empetrichthyinae, as difficult to imagine as it can be today, were not living in isolation from each other. It is now believed that the upper Rio Mezquital, habitat of Characodon, instead of flowing to the Pacific coast in México as it does today, was in fact flowing to the Rio Bravo del Norte (Rio Grande for US) (Conant, 1963; Smith & Miller, 1986), border for a long length between México and the United States. Seemingly Empetrichthyinae habitats in the state of Nevada were also part of this fluvial system. Apparently, geological events have rendered the Rio Bravo shorter than it once was in history.
This event seems to be confirmed by the presence in the valley of Guadiana of a member of the genus Cyprinodon, the pupfishes, a genus associated with Gulf of Mexico and Gulf of California affluents fauna, the species in question being Cyprinodon meeki, belonging to the C. eximius complex of species of the genus, associated with the Rio Conchos in México. C. meeki still nowadays inhabits sympatrically (in the same place) with Characodon lateralis in isolated springs near the towns of Abraham Gonzalez and 27 de Noviembre in Durango.
The relation of the waterways in this area to those in northeastern México and the southern United States is also testified by the historical presence of several other species of fish of northerly ancestry together with Characodon, sharing habitats in the Valley of Guadiana, among them the Cyprinids Gila conspersa (UMMZ 179651), Notropis aulidion (UMMZ 179646), Codoma ornata (UMMZ 179653) and Dionda episcopa (UMMZ 179652), a catfish of the Ictaluridae family Ictalurus barbouri (UMMZ 219050), a sucker of the Catostomidae family Catostomus plebeius (UMMZ 213306) and the diminutive darter of the Percidae family Etheostoma pottsi (UMMZ 179656). Many of those species are unfortunately gone from the valley nowadays.
A reinforcement of the southern origin of Characodon in the area is given by a now very rare (almost extinct in fact) little Atherinid belonging to a group of species that evolved hand by hand with Goodeinae in the basin of the Rio Lerma-Santiago. I refer to the genus Chirostoma and its valley of Guadiana representative Chirostoma mezquital.
Distribution and habitat
The Guadiana valley, found at around 1,800 meters above sea level, is a place with a semi-arid environment at the eastern base of the Sierra Madre Occidental mountains. The mountains, now heavily exploited for its wood by saw mills for many years, were covered in other times with beautiful pine forests, just remaining nowadays in the more remote areas. The ground of the valley is of volcanic origin with black basaltic rocks everywhere.
Weather is mild and never too extreme but air temperatures during the winter for some days can reach below 0 degrees Celsius, while high temperatures can rise to 35 degrees Celsius in the summer. Given the small size of the habitat, the temperature fluctuation should have some impact on the water temperature. However, even in the winter months, maybe due to the water flow, cold air temperatures do not seem to affect greatly in my experience, with temperatures holding around 20 Celsius degrees. It would not surprise me however, that lower temperatures could be recorded in some parts of the habitat, specially those areas where flow has been reduced. I have heard from collectors of temperatures of 16 degrees Celsius.
The city of Durango, with around 430,000 habitants (INEGI, 2000), is found at the mid-western edge of the valley just at the base of the ridge. Many of the habitats of Characodon in the area are unfortunately very close to the city, while some of them have been engulfed by it.
To better explain Characodon, its populations and species, I have divided their distribution into three zones, isolated from each other for apparently the longest time.
Below the falls of Rio Mezquital
The first area comprises springs and creeks flowing into Rio Mezquital down from the beautiful basaltic waterfalls at ”El Salto”. This habitat is now mostly destroyed by the unmerciful pouring of untreated (alright, for the past few years now badly treated) wastes of the big ”Celulosas de México” factory some 25 km east of Durango city by Highway 45. The enjoyment of one of the major scenic areas has been taken away from the local population and visitors by the greed and unconsciousness of at the very least the past policies of this factory and the likely complicity of state and federal authorities. The beautiful underwater landscape down the river is now almost dead, with just the lower forms of life still inhabiting it.
Since the beginning of the 20th century, several researchers recorded collecting spots for Characodon along the lower course of Rio Mezquital below the waterfalls, places that hold Characodon no more. We so far just know of Characodon in this area by two isolated populations: the first at the spring of San Juan near the town of Los Berros; the second at a tiny creek that crosses the little town of Amado Nervo, both bodies of water eventually flowing into Rio Mezquital. Amazingly enough, the two mentioned populations are very distinctive from each other, despite their geographic closeness.
Amado Nervo
Being the most endangered in this area, living solely in a creek crossing the little town of Amado Nervo, this population resembles most closely on in its general appearance its northern cousins of Empetrichthyinae, particularly Crenichthys baileyi. The vulnerability of this population is remarkable. The little creek, running among large trees, over a bed of sand and mud, is no more than an approximate average of a meter wide and no more than 20 centimeters deep, and, to make things worse, it is somewhat polluted by the apparent pouring of untreated sewage from town houses. The creek does not hold truly aquatic vegetation but just terrestrial plants that overshade some areas in the shores (watercress among others) and some filamentous algae. Characodon is always found hiding under the overhanging vegetation. This particular population is maybe the least colorful of all, with a yellow base color both in females and most of the males. The gravid spot in the posterior part of the belly readily identifies females, and the males are of course recognizable by the presence of the andropodium.
The social behavior of Characodon is apparently poorly understood. Although some of the males are gifted with silver bodies and red caudal and anal fins with a distal narrow black bar at the edges, the fact is that just a few of the males of this population show that intense coloration, most males being yellow in overall coloration,. With this I am not suggesting they are ugly though. My own aquarium populations include both types of males and it is clear that the colorful males show dominance over the colonies, which makes also easy its predominance over time.
Characodon is the only fish in Amado Nervo and populates it in a good density, which given the size of the colonizable habitat does not translate directly into a huge population. The fact that Characodon is closely associated with overhanging vegetation is not a surprise, as otherwise the tiny habitat would not provide any refuge against the bigger birds and the heat of the merciless desert sun.
Water chemistry measurements in Amado Nervo show a pH around 8.0, a General hardness of 12 German degrees, Carbonate hardness of 12 degrees and a temperature around 20 degrees Celsius.
Ojo de agua de San Juan
The Ojo de agua de San Juan spring (N23d57.102’ W104d16.121’) at 1807 m over sea level seems to be the most stable of all Characodon habitats, as the water is abundant and pollution is unlikely. The Ojo de Agua itself is a popular place for picnics; it is well taken care of by the local inhabitants and seemingly relies on an abundance of water. The spring is at least 100 meters long by 20 meters wide and is more than two meters deep with a mostly sandy to rocky bottom, with some areas of clay. The water is clear with over two meters of visibility and a healthy abundance of aquatic vegetation, mostly beds of hornwort (Ceratophyllum demersum), Duckweed (Lemna sp.), a Pondweed (Potamogeton sp.) and water lilies (Nymphaea sp.). The habitat is shared with two native species, the Cyprinid Dionda episcopa and the Characinid Astyanax sp. Not all is perfect though, as exotics have unfortunately been introduced, Xiphophorus helleri and Sarotherodon aureus in this case. The effect of this introduction in the long run is uncertain. The snapper turtle Chelydra serpentina is also common in the habitat.
In the ojo de agua de San Juan, the tendency to hide among vegetation is less pronounced among the Characodon lateralis (known commonly in the hobby as Characodon lateralis ”Los Berros”), as the deeper habitat surely offers protection against birds, so individuals confidently wander through the bottom picking on it for food and grazing for algae on the rocks, which shows their seemingly omnivorous habits. In the aquarium, this population seems to be the least aggressive of all.
Coloration in this population is strongly yellow to golden. As in the Amado Nervo fish, some of the males show red caudal and anal fins with thin black margins. This particular population shows a clear pattern on the flanks characterized by an irregular longitudinal succession of black blotches, which are more common on females. Water chemistry measurements at Ojo de Agua de San Juan show a pH around 7.8, a General hardness of 10 German degrees and a temperature around 24 degrees Celsius, with some variation during the year.
Nombre de Dios
Together with the populations from Rio Mezquital, a population that was known to inhabit until not many years ago a spring just west of the town of Nombre de Dios (UMMZ field # Z199015) is now gone for unclear reasons. The river is healthy at this point and it is not affected by the Rio Mezquital pollution (of which this river is an affluent) but seemingly may be affected with some degree of sewage pollution, apparent from the heavy algae growth in the riverbed.
Above the falls
The second area I will write about is located above the waterfalls at El Salto and includes springs located mostly north of the city of Durango in the Guadiana valley and outside of it.
Rio Tunal
Central to this valley and the larger of the habitats is the Tunal river (the name given to the Mezquital river above the falls). Back at the beginning of the 20th century, the renowned ichthyologist Seth Eugene Meek documented the presence of at least ten native fish species from the Rio Tunal. Oh those days! Apparently the introduction of Micropterus salmoides - the terrible black bass; Lepomis macrochirus - the bluegill; Cyprinus carpio - the common carp; and Carassius auratus - the goldfish, for the first time in 1968 (Contreras Balderas, 1975), probably to the Peñon del Aguila dam up the Tunal river with their subsequent colonization of the river downstream from the dam significantly decreased the native species. Collections of the University of Michigan that have taken place after 1985 just document the presence of the bigger endemic species Catostomus plebeius, Gila conspersa and Ictalurus sp., together with the introduced black bass and the bluegill, something that agrees with my own diving experience at the river.
The fact is that Characodon lateralis is no more in the Tunal river, at least since 1968, although it was common in 1963. Populations above the waterfalls that I can testify are still thriving are to be located at small springs, all of them without direct connection to Tunal river, all of them very small and fragile habitats. I am writing of those springs around the little towns of Abraham Gonzalez-27 de Noviembre, Guadalupe Aguilera and a creek in the very upper reaches of Rio Canatlán, a Mezquital headwater affluent, at the town of Los Pinos.
A couple more springs where populations were documented are found one at San Vicente Chupaderos, where apparently they are extirpated either by the introduction of the exotics Goodea atripinnis (another goodeid from far away distribution) and Lepomis machochirus or the activity of the adode-brick producers in the area (now also gone), who have murkied the water in the other times clear water springs. The second one was located at the west side of the town of Cerro Gordo north of the city of Durango; that spring is dry nowadays.
27 de Noviembre - Abraham González
Twenty seven kilometers northeast from Durango city by highway 43, the springs at the eastern side of the town of Abraham Gonzalez form small ponds. Those overflow eastwards forming still more ponds and a small creek (no more than a meter wide at most points), which crosses highway 43 to finally sump at the valley a few kilometers away from the origin, in front of the town of 27 de Noviembre. Some man-dug small intermittent channels no more than 30 cm. deep and 60 cm. wide also flow westwards from the main springs along town streets, holding populations of Characodon lateralis.
At 27 de Noviembre-Abraham Gonzalez Characodon lateralis cohabits nowadays with Cyprinodon meeki, Chirostoma mezquital (very rare), Ictalurus sp. and the exotics Sarotherodon aureus (introduced as a farm fish for human consumption), Lepomis machrochirus and Gambusia senilis, which appeared in the basin in 1976 (UMMZ 203232). Apparently the fact that this habitat offers many extreme areas of shallows with abundant aquatic and overhanging vegetation has facilitated C. lateralis and Cyprinodon meeki to remain thriving with so many exotics.
The habitat is shallow, with a muddy bed and murky water, and an abundance of hornwort (Ceratophyllum demersum) and the presence of Duckweed (Lemna sp.), Pondweed (Potamogeton sp.) and water lilies (Nymphaea sp.). The valley is flat and just low vegetation grows in it, with several isolated trees. As with the rest of the bodies of water the chemistry of the water is very alkaline (up to pH 9) with a moderate hardness. Water temperature in this valley is controlled by the outflow of the springs and apparently never goes below 15 degrees Celsius. We should consider Durango is found in the highlands of the Mexican plateau at parallel 22 and so temperature is more on the temperate side than tropical with temperatures below 0 degrees Celsius being not rare during winter nights. Water never gets warm at all, the warmest being around 25 degrees Celsius in my own measurements.
The particular population of Characodon lateralis at 27 de Noviembre shows a very nice green sheen on the flanks in the adult males, which hold intense red colored caudal and anal fins with a broad black marginal bar, a truly beautiful fish. Females have a base olive green color with some scarce black spotting on the flanks, and the presence of the gravid spot.
Guadalupe Aguilera
The most beautifully colored Characodon lateralis is found in this pristine area. In the flat lands around the town of Guadalupe Aguilera some 60 kilometers north of Durango city, small volcanic rocks cover the whole area. The spring is located in the valley in between the towns of Guadalupe Aguilera and Venustiano Carranza, at a place known as "Laguna Seca" (Dry pond). The whole habitat comprised a small spring at the base of a low mount, it flows in a small heavily vegetated creek some one hundred meters to a swampy area and finally a shallow pond that is absorbed by the valley ground.
Water in this area is clear and the creek bed is composed mostly of mud, although a small pool just at the spring has a sandy bed. Characodon is mostly found the length of the shallow creek hiding in the dense bog vegetation. Very few if any Characodon are to be found at the swamp or the lagoon at the end of the creek, which dries up on the dry season. An incredibly small habitat! What it is so nice about this place is the pristine state of it. Its isolation and very low human population offer us a spring with no exotic species, Characodon lateralis only shares its habitat with the cyprinid Gila conspersa, turtles, an abundance of aquatic insects and an apparently endemic and plentiful leech! (God I hate those!)
This particular population shows a very nice blue sheen on the scales on the sides in the males and the red on unpaired fins is the deepest of any population I know, thick black borders are found in the distal part of the dorsal and caudal fins. The posterior half of the body is also red with blue on the scales. Males also show a yellow orange area in the operculum below the eyes that extends back to the rear of the pectoral fins. The upper part of the body is dark olive green. All adult males are colored the same, as opposed to populations below the falls.
The water parameters in this place correspond closely with those found in other springs in the valley.
Los Pinos
The most northerly population of Characodon lateralis I know of inhabits the headwaters of Rio Canatlán, an upper affluent of Rio Tunal above Peñon del Aguila dam, about some 16 kilometers north of the plaza at down town at Canatlán by highway 39. The whole habitat is a lame remnant of a creek. Talking to the people in the area, they accept the creek had seen better times, losing over the years its flow for unknown reasons. The dry season gave me a sad view of this habitat, with just a few shallow pools remaining in the muddy river bed; this habitat is not there for long!
Characodon in this situation showed a considerable amount of parasites on the sides. The habitat is similar to the above-mentioned areas with an abundance of aquatic and overhanging vegetation in the remaining pools. Truly aquatic plants at the place are however limited to Potamogeton sp. in some areas.
Twenty years ago, a collection by Dr. Robert Rush Miller in this place (UMMZ Field #RRM82-65) produced besides Characodon lateralis the following species; Chirostoma mezquital, Gila conspersa and Lepomis macrochirus (most likely colonizing up from the dam)
Characodon lateralis in this particular place shows a similar coloration to those found south in Guadalupe Aguilera but with a more distributed blue on the scales on the flanks, the yellow in the lower part of the head and behind the pectoral fins shows a more orange tone and the red on the fins is not as intense. But make no mistake, a beautiful fish!
The habitat is found in an area between two mountain ridges which were in past times covered with pine and oak forests; nowadays farms with apple trees are common and the pine forests have receded to the upper parts of the mountains.
El Toboso
But the most unique area of them all is found somewhere between Guadalupe Aguilera and 27 de Noviembre in the volcanic valley. Beside the little town of ”El Toboso”, there is found a small spring cited by Robert Rush Miller as ”El baño de las mujeres,” (N24d16.560’ W104d34.936’ AOSL 1909 m.) which gives it life. The tiny spring, followed by a small creek of no more than two hundred meters empties finally into a shallow pond ”Laguna del Toboso” where it soaks into the ground. ”Laguna del Toboso” is an ephemeral lake that just receives water from the spring during the rainy season, and it has been dry on several occasions, like at least in the dry seasons of 1982, 1983, 1985 (Smith and Miller, 1986) and 2001. The little lake however never fills enough to obtain an outlet from the little basin. It seems that the bed of ”El Toboso” lake is just separated from the Rio Mezquital drainage (Rio La Sauceda basin at that point) by a low divide of less than 50 meters, this divide being the separation between C. lateralis and the C. audax ranges.
The creek at its widest is maybe a meter, running among the black volcanic rocks that give this area an out-of-earth appearance; the creek bed is muddy and bog and Duckweed (Lemna sp.), Pondweed (Potamogeton sp.) and water lilies (Nymphaea sp.) are found in some areas, although Characodon audax here seem to be proficient enough to hide among the many stones. In its deepest natural area, this habitat should not be deeper than 20 centimeters. Again, at least the turtle Chelydra serpentina can be found here (and the bloody leeches!)
In coloration, C. audax is quite unique, with fins (paired and unpaired) velvety black in the males and silver scales on the sides. The lower part of the head and the back part of the pelvic fins shows a salmon coloration. Females are olive green showing the expected gravid spot.
El Toboso is another habitat that remains in good shape in spite of its water exploitation for human use and the man made modification of the course of the creek. Three very small dams have been built to contain the water for cattle drinking, but the Characodon seem to use them well. Some water is also pumped out for the town’s use, but does not seem to be enough to jeopardize the habitat so far. On talking to the people in the area, they agree the habitat has not been reduced in its normal flow, so far. The habitat though is extremely vulnerable.
During my last visit to this place, I visited a nearby spring, El Mescal (N24d16.768’ W104d36.178’ AOSL 1914 m), no more than 2.2 kilometers west of El Toboso, which I was assured contained a Characodon population, my extreme excitement to see how they looked as I rushed to the water was just followed by frustration when I learned no fish could be found in the small area after hours of collecting effort. In later research, I found out that back in 1985 Robert R. Miller had visited the same spring without finding any fish, so, you can’t always trust what you are told by local people!
However, it can’t be ruled out that Characodon audax is not found in some other closely located springs. Dominic Isla (Personal communication, 2002), a well-known livebearer expert, back in 1993, with a group of other aquarists and scientists, was able to collect C. audax from a smaller spring close to ”El Toboso,” at the place known as ”El Tobosito,” at this time I have not visited such place.
The Parras valley
But the sadder part of the Characodon history follows; some three hundred kilometers northeast of the Guadiana valley is the Parras valley, a desert area enclaved in the Chihuahua desert, a locality remote from the areas of distribution of other Goodeids. The Parras valley, with other times beautiful springs, has experienced extensive agriculture development that led to the construction of a dam fed by the springs, where several exotics were introduced, with the consequent extermination of the endemic fish species (IUCN, 1990). From 1880 to 1895, six endemic species were described from the valley. By 1968, just three of the endemics remained (Contreras Balderas, 1975). Among the lost fish there was a third Characodon; C. garmani Jordan & Evermann, 1898. That species would have been the northernmost Goodeinae, but we don’t even have a picture to know how this little fish looked in life, and just one preserved female is the representative of the species. C. garmani seemed to be a more elongated Characodon than either C. lateralis or C. audax, with a shorter anal fin base, shorter pelvic fins and longer pectoral fins (Smith and Miller 1986).
Other species extinct in the valley of Parras were the minnow Stypodon signifer and the pupfish Cyprinodon latifasciatus, which disappeared between 1900 and 1953 (Miller, 1961.)
Biology
Characodon exhibits a large degree of aggressiveness, especially in the males. Males hold loose territories and are intolerant of other adult males; adult females and young individuals remain in groups and are tolerated in territories. In the wild they school loosely and are associated with the bottom of their habitats, from which they pick their food. Diving in Ojo de Agua de San Juan, I have been able to observe them grazing algae from rocks or picking on the sediment. This would be my only clue as to what they eat in the wild, as no snorkeling is possible in other areas (Let alone the leeches!). A plentiful fauna of aquatic insects is also present in all parts of Characodon habitat, so this could possibly be another source of food.
Perhaps due to the nature of their habitat, shallow and mostly clear which facilitates predation, they have a tendency to remain near or among vegetation, mostly overhanging in the edges of creeks or among the bog plants, where they congregate in good numbers.
Females are courted by males, who slightly lean forward and shake their fins and bodies, trying to impress them. If females remain in place, males get side to side and couple with them, achieving fertilization. Contrary to Poeciliids, fertilization is just good for one batch of babies.
Pregnant females retire to the deeper areas of the vegetation, far from the colony activity, where they wait for the time the gestation takes. Babies, in batches from 10 to 40, and sometimes over 50, depending on the size of the female and maybe other factors like isolation time, are due after about 28 days (but this period seems to be somewhat variable), when they are big enough to survive for themselves. Fry are born still retaining the trophotaeniae (umbilical cord), which may persist for as long as a week after birth. Babies try to stay in the safer areas of the habitat.
Aquarium maintenance
Characodon are a pleasure to keep and a serious aquarist could soon be hooked on their long time keeping. Look at me, keeping at home five of the remaining known seven populations, like if I had a thousand tanks!
In my opinion, tank size and fish density is of primary importance, both for them to keep healthy and for you to keep interested, as just the larger tanks give you the pleasure to observe their social interactions. Mine are kept in 130 liter aquariums, where I keep about 25 fish. I have seen failures by friends when they try to keep them in smaller tanks, as males turn out to be too aggressive. It seems dominant males won’t kill other adult males in a single moment, as if they were cichlids, but dominated males will slowly be wasting away until they die, unable to get enough food. I guess that is even more cruel for them.
While Characodon can be kept with other fish, I try to keep them in a one-species only tank, but that is just my preference! They seem to do pretty well with other Goodeids, Poeciliids and small Cyprinids, among other small fish, in my experience, and of course I would guess with many other species of fish, but to know you have to open your eyes and try. C. audax however should not be kept with other Goodeids with black ornaments, like species of Skiffia or Girardinichthys, as C. audax seems provoked by the black markings on them. Characodon lateralis however, does not seem to have a problem with this.
Food is no problem, as they eat anything offered. I try to supply them with live food at least twice each week, while in the meantime I feed them spirulina flakes, krill flakes and my own home cooked food, based on vegetables, shrimp and fish fillet (small fish that eat big fish).
For water parameters I subscribe to good tank maintenance, alkaline water with moderate hardness (But heck I have that kind of water out of the sink, so I can’t talk about experiences with soft acid water on them) and temperature from 20 to 26 Celsius. I can tell you however that they absolutely hate bad water maintenance or very warm water, which makes their life miserable and makes them sick. I however keep some of my populations in temperatures that could go below 10 degrees Celsius for some periods of time during the winter (they are outside my fishroom), without any problem at all, provided temperature does not drop suddenly, which may cause them to contract ick.
Tanks are heavily planted and they seem to love it that way; anyway, they would eat their fry if cover is not provided, so besides the beauty plants bring, the colonies can be self maintained like that.
Conclusions
As you have learned Characodon live in extreme areas; they dwell in habitats that are doomed, most likely even by nature alone, and their likely destiny is being accelerated tremendously by humankind. Most of the populations mentioned are now occupying dying bodies of water, small tracks of tiny creeks, small isolated springs. In most habitats, excepting Ojo de Agua de San Juan, water is no deeper than 30 cms, the creeks are normally no more than a meter wide, so that is why this little fish deserves so badly the attention of serious aquarists in their understanding and long term maintenance.
Of all the places Characodon inhabited, a survey in 1982-83 for Cyprinodon meeki revealed Characodon in just seven springs or spring-fed habitats, plus the upper Rio Canatlán (headwater affluent of Rio Mezquital). Of those springs, nowadays just five still hold Characodon; Amado Nervo, Ojo de agua de San Juan, Abraham Gonzales/27 de Noviembre, El Toboso and Guadalupe Aguilera. The springs at San Vicente Chupaderos, Nombre de Dios and Cerro Gordo have lost their populations. The population at Rio Canatlán remains but seemingly for not too long. This situation is especially tragic if we consider the differences in the populations.
Although you may be wondering ”Where on earth am I going to get this fish?” I should tell you that although these days you can’t expect to find them in aquarium shops, people who keep them around the world are generally more than happy to share their populations with interested parties, provided they have a long-term interest in them. To this end I can serve as middle person.
It is important to mention that the population of San Vicente de los Chupaderos, although apparently extinct in the wild was saved from total extinction by a group of aquarists from Southern California, who collected them back in 1986 in a clear water spring (that they found gone in 1993), Kit Stowell from San Diego, has preserved that population.
Nowadays, the project ”Fish Ark” at the University of Michoacán in México, being inspired and started by Ivan Dibble from England and now headed by Omar Dominguez Domínguez from the University staff, maintain a wonderful collection of all species of Goodeines in the University laboratory, including all Characodon populations, collections that they are willing to share with seriously interested parties.
And so the efforts to keep these fish must be focused on long-term colonies, not just the occasional keeping of a fish for display but also in the hope that one day the habitats can be restored for the fish to be returned to them or for serving as a backup if fragile populations in the wild are lost. With this you may be doing a favor to the fish, but mostly to the humankind, who otherwise will be deprived of the joy of knowing these fantastic jewels of nature.
Acknowledgements
I want to thank James Langhammer, Andreas Tveteraas, Christopher H Stowell, Shane Webb and Mogens Vestergaard for critically reading this manuscript, their corrections and valuable comments. I also want to additionally thank José Luis Blanco Barlés for his help in the correct identification of plants and turtles in the Guadiana valley, and his valuable comments.
References
Conant, Roger; 1963; Semiaquatic Snakes of the Genus Thamnophis from the Isolated Drainage System of the Rio Nazas and Adjacent Areas in Mexico"; COPEIA 1963, No. 3; pages 473-499.
Contreras Balderas, Salvador; 1975; Cambios de composición de especies en comunidades de peces en zonas semiáridas de Nuevo León; Contribuciones del Laboratorio de Vertebrados de la Universidad Autónoma de Nuevo León, Vol. 13, pp. 181-194.
Günther, Albert; 1866; Catalogue of fishes in the British Museum. Catalogue of the Physostomi, containing the families Salmonidae, Percopsidae, Galaxidae, Mormyridae, Gymnarchidae, Esocidae, Umbridae, Scombresocidae, Cyprinodontidae, in the collection of the British Museum. Cat. Fishes i-xv + 1-368
Fitzsimons, John Michael; 1972; A Revision of Two Genera of Goodeid Fishes (Cyprinodontiformes, Osteichthyes) from the Mexican Plateau; Copeia, pp.728-756.
INEGI (Instituto Nacional de Estadística, Geografía e Informática); 2000; Censo Poblacional 2000, Mexico; http://www.inegi.gob.mx.
International Union for Conservation of Nature and Natural Resources (IUCN); 1990; 1990 IUCN red list of threatened animals. IUCN, Gland, Switzerland and Cambridge, U.K. 288 p.
Miller, Robert Rush; 1961; Man and the Changing Fish Fauna of the American Southwest; pap. Michigan Acad Sci Arts Lett. Vol. 46.
Miller, Robert Rush and Fitzsimons, John Michael; 1972; Ameca splendens, a new genus and species of goodeid fish from western Mexico, with remarks on the classification of Goodeidae. Copeia 1971, pp. 1-13.
Mohsen, T.; 1961a; Sur le presence d’un organe copulateur interne, tres évolué chez Skiffia lermae (cyprinodonte, Goodeidae). Comp. Rend. Seanc. Acad. Sci. Univ. Dakar, vol. 252, pp. 3327-3329.
Mohsen, T.; 1961b; Sur le dimorphisme sexual et la presence d’un organe copulateur trés évolué chez cyprinodonte Goodeidae Skiffia lermae Meek. Ann. Fac. Sci. Univ. Dakar, vol. 6, pp. 163-180.
Smith, Michael Leonard and Miller, Robert Rush; 1986; Mexican Goodeid Fishes of the Genus Characodon, with description of a New Species; American Museum Novitates 2851 pp. 1-14, figs 1-4, table 1.
Smith, Michael Leonard and Miller, Robert Rush; 1986; Origin and Geography of the Fishes of Central México; The Zoogeography of North American Freshwater Fishes. John Wiley & Sons, New York. pp. 487-517;
Webb, Shane Anthony; 1998; A Phylogenetic Analysis of the Goodeidae (Teleostei: Cyprinodontiformes); PhD dissertation, University of Michigan, Ann Arbor.
 Characodon audax male from El Toboso, aquarium picture. Photo by Andreas Tveteraas.
Distribution of Characodon in the Guadiana valley in México, the Mexquital river system has been outlined in blue. 1) Characodon lateralis male from Laguna Seca spring, Guadalupe Aguilera; 2) Characodon Audax male, El Toboso; 3) Characodon lateralis male, Abraham González - 27 de Noviembre; 4) The extinct Characodon lateralis from San Vicente de los Chupaderos (Photo by Kit Stowell); 5) Characodon lateralis male, Ojo de Agua de San Juan (also referred as Los Berros); 6) The two different male morphs of Characodon lateralis at Amado Nervo; 7) Location of the "El Saltito" waterfalls. Photo by Juan Miguel Artigas Azas.
Peñon del Aguila Dam in the upper Rio Mezquital (Tunal). Photo by Juan Miguel Artigas Azas.
The remaining of the habitat at Los Pinos, headwaters of Rio Mezquital. The only riverine locality of Characodon lateralis still with the fish, but not for long. Photo by Juan Miguel Artigas Azas.
View of the volcanic valley near Laguna seca, Guadalupe Aguilera. Photo by Juan Miguel Artigas Azas
The spring out of Abraham González as it gets to the Valley in 27 de Noviembre, in this habitat Characodon can still be found with Cyprinodon meeki. Photo by Juan Miguel Artigas Azas
 A Characodon lateralis adult female at Ojo de Agua de San Juan. Photo by Juan Miguel Artigas Azas.
This little creek crossing the little town of Amado Nervo is the whole habitat for a very distinctive population of Characodon lateralis, with males having two different colorations. The watercress visible at the shores provide the necessary cover for the fish. Photo by Juan Miguel Artigas Azas.
Ojo de Agua de San Juan near the town of Los Berros, the biggest habitat where a population of Characodon can be found. The population inhabiting here is highly distinctive. Photo by Juan Miguel Artigas Azas.
A male Characodon audax from the spring Laguna Seca near the town of Guadalupe Aguilera in Durango, Mexico. Photo by Juan Miguel Artigas Azas.
The spring at Laguna Seca, Guadalupe Aguilera. the resulting creek ends no more than a hundred meters from the spring pool in the front. Most Characodon live in the creek among the Watercress. Photo by Juan Miguel Artigas Azas.
The factory "Celulosas y Papel de México" that for many years has polluted the lower course of Rio Mexquital, making dissapear the river Characodon (and all other fihes) populations. Part of the valley of Guadiana can be seen in the background. Photo by Juan Miguel Artigas Azas.
The beautiful but polluted waterfalls at "El salitito" in Rio Mezquital, geographical barrier for Chracodon lateralis distribution. Photo by Juan Miguel Artigas Azas.
 El Toboso creek as it flows after the spring. Photo by Juan Miguel Artigas Azas.
A leech from El Toboso on a local farmer hand. Photo by Juan Miguel Artigas Azas.
The Cathedral at Durango city capitol. Photo by Juan Miguel Artigas Azas.
(Submitted by Grigri 12-5-05)
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Posted on Monday, December 05 @ 15:09:11 CST by goodeids |
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Average Score: 5
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