Conservation status and population trends of Mexican Goodeids, 2011

 

Conservation status and population trends of Mexican goodeid fishes in the wild

 

John Lyons

University of Wisconsin Zoological Museum

2801 Progress Road

Madison, WI  53716 USA

John.Lyons@Wisconsin.gov

 

Introduction

The Mexican fishes of the family Goodeidae have fascinated scientists, naturalists, and aquarists from around the world for nearly a century. But the goodeids are in trouble in the wild. Habitat destruction, water pollution, and exotic species have caused most species to become rare, and several are likely now extinct (Lyons et al. 1998; Contreras-Balderas et al. 2003; De la Vega-Salazar et al. 2005; Domínguez-Domínguez et al. 2005a,b; Jelks et al. 2008). The distribution and abundance of most species has declined precipitously over the last 10-25 years, and the continued survival of many species is precarious (Lyons et al. 1998; Soto-Galera et al. 1998, 1999; De la Vega-Salazar et al. 2003a; Domínguez-Domínguez et al. 2008a; Helmus et al. 2009). There is an urgent need to conserve the remaining intact natural habitats that support healthy goodeid populations and to establish a worldwide network of goodeid captive breeding and maintenance efforts if the disappearance of this group of fishes is to be prevented (De la Vega-Salazar et al. 2003b; Medina-Nava et al. 2005, Domínguez-Domínguez et al. 2006; Helmus et al. 2009).

In this paper I summarize the current (2011) conservation status and population trends of goodeid fishes in the wild in Mexico, updating and expanding upon the status and trends survey from Domínguez-Domínguez et al. (2005a,b). My purpose is to inform aquarium hobbyists of the rapid deterioration of many wild populations and to call attention to the dire prospects for their continued existence without immediate intervention. I hope to encourage hobbyists to support on-the-ground conservation efforts in Mexico and to participate in the long-term captive rearing and preservation of goodeids as a part of their hobby.

 

Sources of Data

I have based my status and trends designations of the Mexican goodeids on a combination of the recent scientific literature, museum specimens, communication with other goodeid scientists, and my own personal field collections, with emphasis on population data collected within the last 10-15 years. Over the last decade or more, I have sampled many different potential goodeid habitats, and I have encountered nearly all of the goodeid species still extant in the wild. I generally follow the taxonomy for goodeids proposed by Miller et al. (2005), but I make some modifications (noted in the text) based on recent genetic analyses by Doadrio and Domínguez-Domínguez (2004) and Webb et al. (2004), and I also include new species described by Radda and Meyer (2003) and Domínguez-Domínguez et al. (2008b). I include 40 goodeid species in my analysis, but recognize that there are populations within several species that probably warrant recognition as separate species.

 

Interpretation of Status and Trends

I designate the conservation status of goodeids based on the terminology and criteria of the World Conservation Union for the protection of rare species (formerly known as the International Union for the Conservation of Nature; IUCN 2001). Note, however, that these are my designations, and they have not been formally recognized by the World Conservation Union. Briefly, “extinct” indicates species for which no specimens have been collected for many years, despite repeated targeted surveys in appropriate habitats. I distinguish between species for which no living specimens exist anywhere on earth (“extinct”) and for which no specimens occur in nature but for which viable captive populations are still present (“extinct in the wild”). “Critically endangered” is applied to species that either persist in the wild at only 1-3 distinct locations with a combined minimum annual population of fewer than 250 adults or that have experienced overall decreases in distribution and abundance of more than 80% within the last 10 years. “Endangered” species either occur at 4-8 distinct locations with a combined minimum annual population of no more than 2500 adults or have decreased in distribution and abundance by 50-70% within the last 10 years. “Vulnerable” species either occur at 9-15 distinct locations with a combined minimum annual population of no more than 10000 adults or have declined by 30-50% in distribution and abundance within the last 10 years. “Nearly threatened” species are uncommon and in decline, but they do not quite meet the criteria for designation as vulnerable or endangered. “Least concern” species have a broader and more stable distribution and abundance and are not in immediate danger of being designated as vulnerable or endangered, although they may be declining in distribution or abundance in some areas.

I also report the official Mexican government status designation from the federal regulations established to protect rare species (“Norma Oficial Mexicana”; NOM 2002).  Three categories apply to the goodeids: “Extinct” – no specimens encountered for many years despite repeated targeted sampling of appropriate habitats; “Endangered” – species rare and in decline and likely to become extinct within the near future without protection and management; and “Threatened” – species uncommon and in decline and likely to become endangered within the near future without protection and management.

 I provide population trends for each species based upon my and my colleague’s observations since the late 1990s. If we have noted the disappearance of a species from a particular location or the substantial decline of a particular population, I classify the species as declining. If no populations have been eliminated and population abundances show no clear trend during this time period, I classify the species as stable. If the species is expanding its range through movement and colonization of new habitats or if a particular population has grown noticeably, I classify the species as increasing. Note that an increase in the known range of a species based on the discovery of a new population that is believed to always have been present does not qualify a species to be classified as increasing.

 

Summary of Goodeid Conservation Status and Population Trends

Although most species are not given an official conservation status by the Mexican federal government, I conclude that nearly all Mexican goodeids qualify for a protected conservation status designation (Table 1). Of the 40 goodeid species I recognize, the Mexican government classifies two as extinct, eight as endangered, and four as threatened. In contrast, I recommend that two goodeid species be designated as extinct, three as extinct in the wild, 16 as critically endangered, seven as endangered, nine as vulnerable, none as nearly threatened, and only three as least concern. My designations are generally the same as in Domínguez-Domínguez et al. (2005a,b), except that Zoogoneticus quitzeoensis has changed from vulnerable to endangered because it has been split into two species (the other being Z. purhepechus), Girardinichthys multiradiatus and Xenotoca melanosoma have been reclassified from nearly threatened to vulnerable, Ilyodon cortesae has been re-classified from vulnerable to critically endangered, Allotoca diazi has declined from endangered to critically endangered, and three formerly critically endangered species are now thought to have become extinct in the wild. Girardinichthys (Hubbsina) turneri is probably completely extinct with no captive populations, whereas Allodontichthys polylepis and, Allotoca goslinei still have viable captive populations.

Most goodeids have declined in range or abundance or both since the late 1990s (Table 1). Of the 37 species still found in nature as of the late 1990s, I classified 23 as declining, 14 as stable, and none as increasing. One species, Goodea atripinnis, did expand its range into the Durango area via human introductions during this time period, but this increase was offset by losses of populations within its native range.

 

Conservation Status and Populations Trends of Species

 

Allodontichthys: This genus consists of four bottom-dwelling species found in fast-flowing areas of streams and rivers on the Pacific slope of west-central Mexico in the Ameca, Armería, and Coahuayana river basins (Lyons and Mercado-Silva 2000; Webb 2002). It is most closely related to Ilyodon and Xenotaenia (Doadrio and Domínguez-Domínguez 2004; Webb et al. 2004).

Allodontichthys hubbsi: Endangered/Stable – This species is known from only four areas in the upper Coahuayana River basin (Lyons and Mercado-Silva 2000). Two of these populations are small, but two, Contla Stream and the nearby upper Tamazula River, are fairly large. None of the populations have shown major changes since the late 1990s (Domínguez-Domínguez et al. 2005b).

Allodontichthys polylepis: Extinct in the Wild?/No records since 2000 (Declining) – As of its initial description in 1988 (Rauchenberger 1988), this species was known from three areas in the upper Ameca River basin. By the late 1990s, the Potrero Grande Stream population had disappeared, but the De la Pola River and Diabalos Stream populations persisted (Domínguez-Domínguez et al. 2005b). However, the last confirmed collections were from the De la Pola River in 1998 and from the Diabalos Stream in 2001. A major drought in 2001-2003 that completely dried the Diabalos Stream and reduced the De la Pola River to small isolated pools with no current may have eliminated the species. Targeted surveys of many streams within the range of A. polylepis in 2004, 2005, 2006, and 2008 failed to find specimens. Based on these surveys, the species is feared to be extinct in the wild, but there is a small chance that a population persists in a remote and inaccessible stream.

Allodontichthys tamazulae: Vulnerable/Stable – Historically know from throughout the Upper Coahuayana River basin (Miller et al. 2005). Pollution from a sugar cane mill near the town of Tamazula has made a portion of the former range of the species in the lower Tamazula River uninhabitable since the 1970’s (Lyons and Mercado-Silva 2000). Since the 1980’s and 1990’s, A. tamazulae has been found at 10 locations, several of which are moderately large. Recent surveys indicate that all of these populations still persist.

Allodontichthys zonistius: Vulnerable/Stable? – Known from about 12 locations in the Armería River basin and one location in the middle Coahuayana River basin (Lyons and Mercado-Silva 2000; Webb 2002). Improved water quality from a sugar mill discharge has led to increases in abundance in the Ayuquila River in the Armería basin near the city of Autlán, but these gains have been offset by population declines further downstream in the Armería River and its tributaries near the city of Colima.

 

Alloophorus: This genus contains a single species, A. robustus, which historically was widespread in the Lerma, upper Santiago (including Lake Chapala), and upper Balsas river basins on the Pacific slope and the endorheic (no outlet) Lake Pátzcuaro, Lake Zirahuén, and Lake Cuitzeo/Grande de Morelia River basins in central Mexico (Miller et al. 2005). The species has broad habitat tolerances, occurring in lakes, springs, and rivers. In the past, A. robustus was harvested for human food in many places, although currently most populations are too small to support a significant fishery.

Alloophorus robustus: Vulnerable/Declining. Once known from over 50 different localities, this species now persists at about 25. Since the 1990s, it has disappeared from Lake Chapala and the adjacent Santiago and Lerma rivers, from the Laja River, a major Lerma tributary, and from Lake Yuriria. The species has become rare in the Lake Cuitzeo/Grande de Morelia, Lake Pátzcuaro and Lake Zirahuén basins, persisting only in spring areas and small tributaries (Lyons et al. 1998; Soto-Galera et al. 1998, 1999; Mercado-Silva et al. 2006; Domínguez-Domínguez et al. 2008b). Losses have been from a combination of declines in water quality and quantity (e.g., Chapala, Cuitzeo) and predation and competition from introduced non-native species (e.g., variable platyfish Xiphophorus variatus (Poeciliidae) in the Laja River; largemouth black bass Micropterus salmoides (Centrarchide) in Lake Zirahuén). Remaining strongholds include the La Mintzita Springs in the Lake Cuitzeo basin near the city of Morelia, Lake Zacapu in the headwaters of the Angulo River drainage, a Lerma River tributary, and the Duero River drainage, also a Lerma River tributary, including the La Luz and Orandino spring lakes.

 

Allotoca: This is the most diverse genus of goodeids, with seven or eight currently recognized species and probably one or more additional undescribed species (Doadrio and Domínguez-Domínguez 2004; Webb et al. 2004; Miller et al. 2005). Overall, the genus had a historically wide range in the Armería, Ameca, Magdalena, Lerma, Cuitzeo/Grande de Morelia, Pátzcuaro, Zirahuén, and upper Balsas basins on the Pacific slope of central Mexico. However, the individual ranges of most species are (or were) quite small. Some populations of Allotoca that have disappeared may have represented additional undescribed species. For example, a single distinctive Allotoca specimen was collected from the upper Armeria River basin in the 1930s and a different but also distinctive Allotoca specimen was found in Lake Chapala in the 1960s, but no Allotoca have been found in either location since. Thus, whatever species these specimens represented, new or otherwise, they have been eliminated (Lyons et al. 1998).

Allotoca catarinae: Vulnerable/Stable – Known from about 10 locations in the upper Rio Cupatitzio drainage in the upper Balsas River basin near the city of Uruapan and possibly also in the Lake Cuitzeo/Grande de Morelia and Lake Pátzcuaro basins, although the taxonomic status of specimens from outside of the Río Cupatitzio drainage is uncertain (Doadrio and Domínguez-Domínguez 2004). None of these populations are particularly large, but all have persisted since the late 1990s.

Allotoca diazi: Critically Endangered/Declining – Older literature (e.g., Meek 1904; Mendoza 1962) placed this species in the genus Neoophorus, but recent morphological and genetic analyses indicate that Allotoca is more appropriate (Meyer et al. 2001; Doadrio and Domínguez-Domínguez 2004; Webb et al. 2004). Currently, A. diazi is known from only three small areas in the Lake Pátzcuaro basin, the only basin where it occurs. It has declined dramatically in Lake Pátzcuaro proper and persists only as a remnant population there. The only remaining large population is in the Molino de Chapultepec Springs near the town of Pátzcuaro.

Allotoca dugesii (spelled dugesi in older literature; e.g., Smith and Miller 1980): Endangered/Declining – The widest ranging of the Allotoca species, historically known from much of the middle and lower Lerma and upper Santiago river basins on the Pacific slope and the endorheic Lake Pátzcuaro, Lake Zirahuén, and Lake Cuitzeo/Grande de Morelia River basins (Miller et al. 2005). Currently, the species is known from only six locations. A new population was recently discovered in a spring along the Duero River in the Lerma River basin near the town of Etúcuaro, but it is very small. Recent surveys have documented the species disappearance from the Santiago and Zirahuén basins where it was once widespread and common. Strongholds are the Molino de Chapultepec Springs and the La Maiza Springs in the Cuitzeo/Grande de Morelia basin near the city of Morelia. Domínguez-Domínguez et al. (2002) published observations on larval feeding of this species that will useful in the maintenance of captive populations.

Allotoca goslinei: Extinct in the Wild?/No records since 2004 (Declining) – Known from only a small tributary of the Ameca River, the Potrero Grande Stream, and the Ameca River itself near the mouth of the stream in the upper Ameca River basin near the city of Ameca (Smith and Miller 1987). The species had been eliminated from the Ameca River by the late 1990s but was still moderately common in the headwaters of the Potrero Grande Stream. In the early 2000s, the non-native green swordtail Xiphophorus helleri (Poeciliidae) became established in the Potrero Grande Stream. As swordtail numbers increased, the abundance of A. goslinei dropped rapidly, presumably from competition or predation on larvae. The last specimen of A. goslinei was collected in 2004, and none could be found in targeted surveys in 2005, 2006, and 2007 (Helmus et al. 2009). Based on this, A. goslinei is feared to be extinct in the wild, although it slightly possible that a small population persists in an isolated area of the stream not yet invaded by the swordtail.

Allotoca maculata: Critically Endangered/Declining – This species was described from the endorheic Lake Magdalena basin in west-central Mexico, where it was thought to be endemic, that is, found nowhere else (Smith and Miller 1980). Believed extinct by the late 1980s (Miller et al. 1989), this species was rediscovered in the 1990s at two locations, Lake Magdalena and the nearby but hydrologically isolated headwaters of the San Marcos River in the Ameca River basin near the town of Etzatlán (includes Palo Verde Reservoir, ditches at Granja Sanguaripa, and the San Marcos River). However, genetic analyses indicate that the San Marcos populations likely represent a new but as-of-yet undescribed species (Doadrio and Domínguez-Domínguez 2004). Regardless of taxonomic status, populations at both locations are very low and decreasing. During a 2008 survey, it required over an hour of intensive sampling to collect two individuals from Lake Magdalena, and during this same survey no specimens were found at the San Marcos River sites. Populations are threatened by extensive drying of habitats in the San Marcos River and possibly competition with non-native blue tilapia Oreochromis aureus (Cichlidae) in Lake Magdalena.

Allotoca meeki: Critically Endangered/Declining – Known only from the endorheic Lake Zirahuén basin, where it was once common. The introduction of non-native largemouth black bass, a fish predator, eliminated the species from Lake Zirahuen by the late 1990s (Domínguez-Domínguez et al. 2005b). A population of A. meeki persisted in Lake Opopeo in the headwaters of a tributary system, but by the 2000’s bass had invaded this lake, and no A. meeki could be found there in a 2011 survey. Three individuals were encountered in a small shallow outlet of the lake, but the prospects for the long-term survival of the species in this outlet are bleak.

Allotoca zacapuensis: Critically Endangered/Stable – This species was described just recently in 2001 (Meyer et al. 2001), and is known only from Lake Zacapu in the headwaters of the Angulo River drainage in the Lerma River basin. Within the lake it is known from only two spring areas where it is rare but apparently relatively stable in numbers (Domínguez-Domínguez et al. 2005b).

 

Ameca: This genus consists of a single species, A. splendens, which, until recently was thought to be restricted to the Teuchitlán Springs and their outlet in the upper Ameca River basin on the Pacific slope of west-central Mexico (Miller et al. 2005). However, within the last five years, two new populations have been discovered in adjacent basins.

Ameca splendens: Critically Endangered/Stable? – This species is known from the Teuchitlán Springs and was recently discovered in the El Moloya Springs in the endorheic Lake Magdalena basin and the El Molino pond in the endorheic Lake Sayula basin (both adjacent to the Ameca basin) by Omar Domínguez-Domínguez, (Universidad Michoacana de San Nicolas de Hidalgo, Morelia, Mexico). Based on his unpublished analyses, the taxonomic status of the two new populations is not completely resolved, but both are morphologically and genetically very similar to Teuchitlán A. splendens and are probably the same species. The Teuchitlán population occupies only a limited part of the springs but is moderately large and seems stable (López-López et al. 2004). However, the El Moloya and El Molino populations appear to be very small. In 2010, the El Molino pond dried up during a drought, and the current status of the population there is unknown. Bailey et al. (2007) provide an analysis of genetic diversity within the Teuchitlán Springs population.

 

Ataeniobius: This genus is represented by a single species, A. toweri, and is limited to the thermal-spring lakes in the headwaters of the Verde River system in the Pánuco River basin on the Atlantic slope of central Mexico (Miller et al. 2005).

Ataeniobius toweri: Critically Endangered/Stable – Known from the Media Luna and Los Anteojitos lakes and their outlets. The species associates closely with dense vegetation making it difficult to survey, but the populations appear to be small and stable. Both lakes are protected as reserves, but groundwater pumping in the region that may reduce spring inputs into the lakes and the introduction of non-native species both threaten the continued survival of A. toweri (Domínguez-Domínguez et al. 2005b).

 

Chapalichthys: This genus has two currently recognized species, one in the Lake Chapala basin and the other in a nearby portion of the upper Balsas River basin, both on the Pacific slope of central Mexico (Miller et al. 2005).

Chapalichthys encaustus: Vulnerable/Declining – This species was formerly abundant throughout nearshore areas of Lake Chapala and was also encountered in adjacent areas of the Lerma and Santiago rivers and their tributaries (Lyons et al. 1998). Since the late 1990s, C. encaustus has disappeared from the mainstem Santiago and Lerma rivers due to pollution and has become much less common in Lake Chapala owing to the invasions of the non-native livebearers Poecilia sphenops and Gambusia yucatana (Poeciliidae) (Becerra-Muñoz et al. 2003). Chapalichthys encaustus still persists in the lower portion of the Duero River drainage, a Lerma River tributary, including the La Luz and Orandino lakes, and also in Cajititlán and Los Negritos lakes, both near Lake Chapala. In 2005, a single individual was collected from La Vega Reservoir in the upper Ameca River basin, probably introduced during a stocking of blue tilapia, but there is no indication that C. encaustus has become established there (Pablo Gesundheit-Montero, Universidad Nacional Autónoma de Mexico, Mexico City, personal communication).

Chapalichthys pardalis: Critically Endangered/Stable – This species is known from only two areas in the upper Balsas River basin, the San Juaníco Lake and the Tocumbo Springs, located about 25 km downstream on the outlet of the lake (Miller et al. 2005). For many years the San Juaníco population was considered a separate species, C. peraticus (e.g., Domínguez-Domínguez et al. 2005b), but recent genetic and morphological analyses (Miller et al. 2005; Kyle Piller, Southeastern Louisiana University, Hammond, Louisiana, USA, personal communication) indicate that the there are insufficient differences between the two populations to warrant separate species status. The Tocumbo population is small and is limited to a spring system that has been heavily modified as a swimming area. The San Juaníco population is larger and occupies a bigger area, but is nonetheless still small.

 

Characodon: This distribution of this genus is separate from that of other Mexican goodeids, being found on the Pacific slope of northwestern Mexico in the states of Durango and Coahuila far to the north of the other species. Three species are recognized, one long extinct and the other two critically endangered and declining.

Characodon audax: Critically Endangered/Declining – C. audax and C. lateralis are known from a series of semi-isolated springs and their outlets in Tunal/Durango River drainage in the upper Mezquital River basin. When first described (Smith and Miller 1986), C. audax was believed restricted to a single spring system near the town of El Toboso. The population here was morphologically distinctive from other Characodon populations. All other populations in the Tunal/Durango River drainage (~17 known historically) were considered C. lateralis. However, recent genetic analyses reveal little difference between the El Toboso population and many other Characodon populations (Omar Domínguez-Domínguez, personal communication). The genetic analyses suggest that populations from spring systems above the El Salto waterfall on the Tunal River (e.g., Los Pinos, Guadalupe Aguilera (Laguna Seca), Cerro Gordo, San Vincente de Chupaderos, Presa Peñon del Aguila, El Toboso, El Tobosito, Abraham González, 27 de Noviembre, Puente Piño Suarez) are similar enough to be considered the same species, in which case they could all be called C. audax. Populations from springs below the waterfall (e.g., Los Berros (Ojo de Agua de San Juan), La Constancia, Amado Nervo) are genetically distinct enough to be considered a separate species and could be called C. lateralis. However, morphological, coloration, and behavioral differences exist among populations that are similar genetically, and a detailed revision of the genus being conducted by Michael Tobler (Oklahoma State University, Stillwater, Oklahoma, USA, personal communication) needs to be completed before the two species can be adequately defined and delineated.

Regardless of how they are defined, both C. audax and C. lateralis are on the verge of going extinct. As of the 1990’s there were about 11 populations still extant, but as of 2011 only seven remained, and two of these (El Toboso – C audax; Amado Nervo – C. lateralis) had declined sharply and had almost disappeared (Michael Tobler and Juan Miguel Artigas-Azas, San Luis Potosí, Mexico, unpublished data). The other five populations (Guadalupe Aguilera, Abraham González, and 27 de Noviembre (C. audax?) and Los Berros and La Constancia (C. lateralis?) remained stable but were very small,

Characodon garmani: Extinct/No records since 1890s – This species is known from only a single female individual, collected from the Parras Valley in Coahuila prior to 1895 (Fitzsimons 1972; Smith and Miller 1986; Miller et al. 2005). This valley had no outlet to the sea, and the habitat there was heavily modified before C. garmani could be studied or protected in captivity. Many attempts have been made to find the species over the last 60 years with no success, and it is clearly extinct (Miller et al. 1989).

Characodon lateralis: Critically Endangered/Declining – See C. audax.

 

Girardinichthys: This genus occurs in central Mexico in several different basins. Historically, Girardinichthys was believed to have only two species, G. multiradiatus and G. viviparous. However, Radda and Meyer (2003) proposed combining the genus Hubbsina with Girardinichthys and demoting Hubbsina to a subgenus, which would expand Girardinichthys to four species. I accept this new taxonomy here, but note that that only limited data have been presented to support combining the two genera, and the name change is not accepted by all ichthyologists (e.g., Domínguez-Domínguez et al. 2005b; Miler et al. 2005).

Girardinichthys ireneae: Critically Endangered/Declining – Until recently, this species was considered to be part of Hubbsina turneri (Domínguez-Domínguez et al. 2005; Miller et al. 2005). When Radda and Meyer (2003) subsumed Hubbsina within Girardinichthys, they split the former H. turneri into two species, G. ireneae and G. turneri. Girardinichthys ireneae, as currently defined, is known only from the upper portion of the Angulo River drainage of the Lerma River basin, primarily in Lake Zacapu and a few smaller spring-fed lakes nearby. It appears to have disappeared from the smaller lakes since the 1990’s and persists only in Lake Zacapu.

Girardinichthys multiradiatus: Vulnerable/Stable? – This species was known historically from about 16 locations located just northwest, west, and south of greater Mexico City including 13 streams and wetlands in the upper the Lerma River basin and single sites in the headwaters of the Balsas River basin on the Pacific slope, the endorheic (no outlet) Lake Zempoala system, and the Taxingu Reservoir in the upper Pánuco River basin on the Atlantic slope (Domínguez-Domínguez et al. 2005b). Distribution and abundance of G. multiradiatus declined substantially in the Lerma basin over the 20th century, and the seven remaining populations there are now small and isolated, but these populations seem to have been stable since the late 1990s. The Balsas, Zempoala, and Taxingu populations also still persist.

Girardinichthys (Hubbsina) turneri: Extinct/No records since 1980s – As defined by Radda and Meyer (2003), this species was limited to Yuriria Lake in the Lerma River basin and the nearby endorheic Lake Cuitzeo/Grande de Morelia River basin. These two areas have been heavily polluted and modified, and no G. turneri have been observed in either area since the late 1980s despite repeated and intensive targeted sampling, strongly suggesting that the species is extinct in the wild (Soto-Galera et al. 1999; Domínguez-Domínguez et al. 2005b). Unfortunately, it appears that no captive populations exist, so the species may be completely extinct.

Girardinichthys viviparus: Critically Endangered/Stable? – Historically, this species was endemic to and abundant in the many lakes and wetlands of the endorheic Valley of Mexico, where Mexico City is located (Miller at al. 2005). Construction of a canal to drain the Valley allowed the species to colonize a small spring along the Tula River in the headwaters of the Pánuco River on the Atlantic slope where the species still remains in small numbers (Edmundo Díaz-Pardo, Universidad Autónoma de Querétaro, Querétaro, Mexico, personal communication). The drainage of the Valley coupled with the rapid expansion of Mexico City led to a drastic decline in the distribution and abundance of G. viviparus. During the 20th century, the species was eliminated from Lake Texcoco and Lake Chalco and became rare in Lake Xochimilco and Lake Zumpango, all of which have become greatly reduced in size, highly polluted, and dominated by non-native fish species (Domínguez-Domínguez et al. 2005b). Despite poor environmental conditions, the Xochimilco and Zumpango populations have managed to survive up to the present. The best remaining population is in the artificial Lake Mayor in Chapultepec Park in downtown Mexico City. This population persists in moderate numbers despite poor water quality, but it is vulnerable to drainage of the lake for maintenance.

 

Goodea: I consider this genus to have only one species, but some ichthyologists and aquarists recognize one or two additional species (e.g., Doadrio and Domínguez-Domínguez 2004). This genus is the most widespread of the Goodeids and occupies the broadest range of habitats, with a native distribution that encompasses most of the highlands of central Mexico including streams, rivers, wetlands, springs, lakes, and reservoirs (Miller et al 2005).

Goodea atripinnis: Least Concern/Declining – This species has the largest distribution of any goodeid species. Its native range includes the Lerma, upper Santiago (including Lake Chapala), upper Ameca, upper Armería, and upper Balsas river basins on the Pacific slope, the endorheic Lake Zirahuén, Lake Pátzcuaro, and Lake Cuitzeo/Grande de Morelia River basins in central Mexico, and the upper Pánuco River basin on the Atlantic slope. Many years ago it invaded and became established in the endorheic Valley of Mexico, and an introduced population was recently discovered in the upper Mezquital River basin within the range of Characodon near Durango (Michael Tobler, personal communication). Some early authors (e.g., Meek 1904; Mendoza 1962) considered the Lake Pátzcuaro population a different species, G. luitpoldi, but recent genetic and morphological analyses indicate that this population is not distinct from G. atripinnis (Doadrio and Domínguez-Dominguez 2004; Webb et al. 2004; Clyde Barbour, Wright State University, Dayton, Ohio, USA, personal communication; Kyle Piller, personal communication). Other authors consider the Pánuco River basin populations a distinct species, G. gracilis (e.g., Doadrio and Dominguez-Domínguez 2004; Domínguez-Domínguez et al. 2005b). Although there are minor genetic and morphological differences between Pánuco River basin populations and other Goodea populations, I do not consider them large enough to warrant recognition of G. gracilis as a separate species.

Goodea atripinnis remains common in many areas and is probably still the most abundant goodeid species overall, but its distribution and abundance have steadily declined over the last 25 years (Lyons et al. 1998; Soto-Galera 1999; Domínguez-Domínguez et al. 2005b; Mercado-Silva et al. 2006). Historically the species supported commercial fisheries in the larger lakes where it occurred, but in recent years it has been eliminated from Lake Zirahuén, reduced to a small remnant population in Lake Pátzcuaro, and greatly decreased in number in Lake Chapala and Lake Cuitzeo, largely owing to predation by and competition with non-native fish species. Only a handful of populations persist in the upper Pánuco River basin, primarily because of water diversions and groundwater pumping, which have eliminated habitat. Pollution and habitat modifications have devastated populations in many areas of the Lerma and upper Santiago basins.

 

Ilyodon: This genus is found in fast-flowing streams in the upper Ameca, Armería, Marabasco, Coahuayana, and Balsas basins in the mountains of west-central Mexico. It is most closely related to Allodontichthys and Xenotaenia (Doadrio and Domínguez-Domínguez 2004; Webb et al. 2004).There is substantial morphological variation within and among populations of Ilyodon, and the taxonomy of several species is unresolved. I recognize three species, but some ichthyologists and aquarists recognize as many as five or six or as few as one or two.

Ilyodon cortesae: Critically Endangered/Stable? – This species was recently described (Paulo-Maya and Trujillo-Jimenez 2000), and is known from only three nearby locations in the Tacámbaro River drainage in the upper Balsas River basin. However, some ichthyologists question the validity of this species and suggest that it may be merely a variant of I. whitei (Miller et al. 2005; Omar Domínguez-Domínguez, personal communication). Little is known about the overall distribution and abundance of I. cortesae, which is found in a remote and difficult-to-access area, but known populations are small and localized.

Ilyodon furcidens: Least Concern/Declining – As I define it, this species is widely distributed and common in the Armería, Marabasco, and upper Coahuayana river basins and uncommon in the upper Ameca River basin. Recent genetic analyses suggest that populations may also occur in parts of the Balsas River basin, although more specimens and analyses are needed to confirm this (Kyle Piller, personal communication). Because of this uncertainty about the identity of some Balsas populations, some authors consider I furcidens a synonym of (i.e., the same species as) I. whitei (Doadrio and Domínguez-Dominguez 2004). Two morphotypes of I. furcidens are present in many areas of the Armería, Marabasco, and Coahuayana basins (Lyons and Navarro-Pérez 1986), and these were long thought to be two different species, the narrow-mouthed form, I. furcidens and the wide-mouthed form, I. xantusi. However, work by Turner et al. (1983, 1985) and Grudzien and Turner (1984) demonstrated that narrow-mouthed females could produce both narrow-mouthed and wide-mouthed offspring, as could wide-mouthed females, proving that the two morphotypes were part of the same species. Ilyodon furcidens was the older of the two names and thus had priority, so the name I. xantusi is no longer considered valid. Some ichthyologists and aquarists consider populations from the upper Ameca River basin to be a separate species, I. “amecae” (Doadrio and Domínguez-Domínguez 2004). However, genetic and morphological differences between Ameca and Armería populations are small (Kyle Piller, personal communication), and I do not consider the Ameca populations worthy of separate species status. Furthermore, the name I. “amecae” has never been formally described in the scientific literature, and under the rules of scientific nomenclature it is therefore not appropriate for use in scientific or aquarium publications.

Ilyodon furcidens is often the most common species at the localities where it occurs. However, numbers appear to be decreasing since the 1990’s. Populations have declined or disappeared from several streams in the Ameca River basin because of shrinking water levels and invasions of non-native species. Within the Armería River basin, the expansion of the non-native largemouth black bass, a top predator, has apparently resulted in the near elimination of the I. furcidens from long stretches of the Ayuquila River (Norman Mercado-Silva, Universidad de Guadalajara, Autlán, Mexico, personal communication).

Ilyodon whitei: Vulnerable/Declining – As I define it, this species is limited to the Balsas River basin, where it occurs in about 12 different areas. Specimens from a tributary to the Balsas River near Ciudad Altamirano in the state of Guerrero were described as a separate species, I. lennoni (Meyer and Forster 1983), but I and most other ichthyologists (e.g., Doadrio and Domínguez-Domínguez 2004; Domínguez-Domínguez et al. 2005b; Miller et al. 2005) do not consider this name to be valid. Many populations of I. whitei have declined or disappeared over the last 25 years, largely because of predation by or competition from non-native fish species (e.g., Contreras-MacBeath et al. 1998). Non-native species now dominate many areas of the Balsas River basin.

 

Neoophorus: This genus currently consists of one species, N. regalis, which some ichthyologists place in the genus Allotoca (Webb et al. 2004; Miller et al. 2005). I concur with Doadrio and Domínguez-Domínguez (2004) that genetic information support recognition of Neoophorus as a distinct genus, but additional genetic and morphological studies to confirm this view are warranted.

Neoophorus regalis: Critically Endangered/Declining – At present this species survives in only one small unnamed stream near the city of Los Reyes, Michoacán, in the upper Balsas River basin. Historically, the species was widespread and moderately common in streams and wetlands near Los Reyes (Miller et al. 2005), but distribution and abundance have declined steadily over the last 25 years as wetlands have been drained and streams have been channelized and diverted for agriculture. Introductions of non-native green swordtails and blue tilapia may also have contributed to losses. As of the early 2000’s, N. regalis was known from four locations (Domínguez-Domínguez et al. 2005b), but 2008 and 2011 surveys found the species at only one of these locations, where it was uncommon.

 

Neotoca: This genus consists of one species, N. bilineata, which many ichthyologists place in the genus Skiffia (Webb et al. 2004; Domínguez-Domínguez et al. 2005b; Miller et al. 2005). I concur with Doadrio and Domínguez-Domínguez (2004) that genetic information supports recognition of Neotoca as a distinct genus, but as is the case for Neoophorus, additional genetic and morphological studies to confirm this view are warranted.

Neotoca bilineata: Critically Endangered/Declining – Historically, this species was reported from three distinct areas: Lake Chapala and adjacent portions of its outlet, the upper Santiago River; the Lerma River and its tributary the Laja River and Lake Yuriria in the middle Lerma River basin; and the endorheic Lake Cuitzeo/Grande de Morelia River basin near the city of Morelia (Miller et al. 2005). The Lake Chapala area records are from the early 1900’s, and no individuals have been collected there for at least 60 years (Lyons et al. 1998). The last middle Lerma basin records are from the 1990’s, and recent surveys have not encountered any specimens (Soto-Galera et al. 1998; Mercado-Silva et al. 2006). The only remaining populations are in the Lake Cuitzeo/Grande de Morelia River basin (Domínguez-Domínguez et al. 2005b). Pollution and habitat modifications had eliminated the species from Lake Cuitzeo and from most of the Grande de Morelia River drainage by the 1990’s, leaving only four surviving populations (Soto-Galera et al. 1999). Two of these have since disappeared, and the long-term survival of this species in the wild is highly uncertain (de la Vega-Salazar 2003a; Domínguez-Domínguez et al. 2005b).

 

Skiffia: As I define it, this genus has three species, all limited to central and west-central Mexico where they are found mainly in springs and spring-fed lakes and streams (Miller et al. 2005).

Skiffia francesae: Extinct in the Wild/No records since 1970’s – This species has long been thought to be endemic to the Teuchitlán Springs in the upper Ameca River basin. It was already believed extinct in the wild when it was first formally described as a species in 1978 (Kingston 1978; Miller et al. 1989). Fortunately, numerous captive populations exist in North America and Europe, although many of these are inbred (Domínguez-Domínguez et al. 2005b). In 2007, Omar Domínguez-Domínguez discovered a new population of Skiffia that suggested that S. francesae might still persist in wild. These fish came from the El Molino pond in the endorheic Lake Sayula basin, which is located about 80 km south of the Teuchitlán Springs. Some individuals from El Molino looked identical to S. francesae, whereas others had pigmentation that was more reminiscent of S. multipunctata (James Langhammer, Royal Oak, Michigan, USA, personal communication). Genetically, the El Molino fish were more similar to S. francesae than to S. multipunctata (Omar Domínguez-Domínguez, personal communication). Two interpretations of the status of the El Molino fish are possible. They may represent a disjunct and somewhat distinctive population of S. francesae, in which case the species is not extinct in the wild. Alternatively, they may represent a new and undescribed species of Skiffia different from S. francesae, in which case S. francesae still remains extinct in the wild. Further study will be needed to resolve the issue, but regardless, the El Molino population is of great importance. Regrettably, in 2010, the El Molino pond dried completely during a drought, and the current status of the wild population is unknown. Fortunately, Omar Domínguez-Domínguez had established a captive population in Morelia before this happened.

Skiffia lermae: Endangered/Declining – The historical range of this species encompassed many sites in central Mexico including Lake Zacapu, Lake Yuriria, and the Laja River in the middle Lerma River basin, and the endorheic Lake Pátzcuaro, Lake Zirahuén, and Lake Cuitzeo/Grande de Morelia River basins. Distribution and abundance of S. lermae have declined steadily over the last 50years, with continued losses through the 2000’s. The species has disappeared from the Laja River, Lake Yuriria, Lake Cuitzeo, and the entire Lake Zirahuén basin, and has become uncommon and limited to a few small springs in the Lake Pátzcuaro and Grande de Morelia River basins (Lyons et al. 1998; Soto-Galera et al. 1998, 1999; de la Vega-Salazar 2003a; Domínguez-Domínguez et al. 2005b, 2008a; Mercado-Silva et al. 2006). At present, about six populations remain, the largest of which are in Lake Zacapu in the Lerma River basin, the Molino de Chapultepec Springs in the Lake Pátzcuaro basin, and the La Mintzita Springs in the Grande de Morelia River basin.

Skiffia multipunctata: Endangered/Declining – This species was found historically in Lake Chapala, the upper part of the Santiago River basin near the city of Guadalajara, including Lake Cajititlán, and the lower Lerma River basin, particularly the Duero River basin (Domínguez-Domínguez et al. 2005b). Pollution, habitat modifications, and introductions of non-native species have eliminated S. multipunctata from Lake Chapala, the Santiago River basin, and parts of the lower Lerma River basin (Lyons et al. 1998; Soto-Galera et al. 1998). The only area where the species remains is the Duero River drainage, but even there populations have disappeared from the lower portion of the drainage because of stream channelization and water diversions for agriculture and probably also from Lake Camécuaro National Park because of introductions of non-native largemouth black bass. Only six or seven viable populations remain, with the largest found in the spring-fed La Luz and Orandino lakes. Information on the larval ecology of S. multipunctata in captivity is provided by Escalera-Vásquez et al. (2004) and Kelley et al. (2005).

 

Xenoophorus: As presently defined, this genus has only one species, X. captivus, which is known from three hydrologically and geographically isolated areas located to the northeast of the main body of the goodeids species on the Atlantic slope in the states of Zacatecas and San Luis Potosí (Miller et al. 2005). Populations from each area are somewhat distinctive morphologically and genetically, and they were formerly considered different species (Fitzsimons 1979).

Xenoophorus captivus: Critically Endangered/Declining – The distribution and abundance of this species has shrunk considerably since the 1970’s and 1980’s owing to groundwater pumping and spring diversions that have lowered water levels and degraded water quality. The population in the endorheic Illescas spring system on the border of Zacatecas and San Luis Potosí appears to be extirpated, with the last confirmed collection from the 1990’s (Domínguez-Domínguez et al. 2005b). The current status of the populations in three small springs, Venados, Moctezuma, and Agua de Enmedio, located in a small endorheic basin in northern San Luis Potosí, is uncertain, and perhaps only the Venados populations still remains (Omar Domínguez-Domínguez, personal communication). Three or four small and somewhat interconnected populations are known from the upper portion of the Santa María del Río River drainage in the upper portion of the Pánuco River basin in southern San Luis Potosí. Of these, the Tierra Quemada River population appears to be in the best shape, but even there fish density is low.

 

Xenotaenia: This genus has a single species, X. resolanae, limited to streams and small rivers in the Marabasco and Purificación river basins on the Pacific slope of west-central Mexico (Lyons 1996). It is most closely related to Allodontichthys and Ilyodon (Doadrio and Domínguez-Domínguez 2004; Webb et al. 2004; Miller et al. 2005).

Xenotaenia resolanae: Vulnerable/Stable –This species is known historically from a total of 16 locations. Within the Purificación River basin, water pollution from sugar mill discharges, human sewage, and animal wastes had eliminated or reduced most populations by the 1980s, but since then remaining populations seem to have stabilized (Lyons and Navarro-Pérez 1990; Lyons 1996; Domínguez-Domínguez et al. 2005b). In the upper Marabasco River basin, which has less human development, the species has seen little decline, although most populations are small. Overall, about 10 total populations still exist.

 

Xenotoca: Based on the morphological analyses of Fitzsimons (1972), this genus is currently considered to have three species, X. eiseni, X. melanosoma, and X. variata. However, Webb (1998), in his Ph.D. dissertation, provided genetic and morphological evidence that X. eiseni and X. melanosoma are not the closest relatives of X. variata. He proposed that X. eiseni and X. melanosoma be placed in a new and separate genus “Xenotichthys”. Subsequent genetic analyses supported the distinctiveness of X. eiseni and X. melanosoma from X. variata (Doadrio and Domínguez-Domínguez 2004; Webb et al. 2004). Consequently, in some publications, the two species were referred to as “Xenotoca” eiseni and “Xenotoca” melanosoma to indicate the likelihood that their genus would eventually change (e.g., Miller et al. 2005). To date, the proposal by Webb (1998) to apply “Xenotichthys” as the genus for X. eiseni and X. melanosoma has not yet been formally published. By the rules of scientific nomenclature, until this new genus name is described and diagnosed in a scientific journal, it is not appropriate for use in scientific or aquarium publications.

Xenotoca eiseni: Endangered/Declining – This species, as currently defined, has a wide range in west-central Mexico, encompassing portions of the lower Santiago River basin, the upper portions of direct Pacific drainages near the cities of Tepic and Compostela in the state of Nayarit, the endorheic Magdalena Lake and Atotonilco Lake basins, and the upper Ameca, Armería, and Coahuayana river basins (Miller et al. 2005). However, recent genetic and morphological analyses indicate that populations in the Magdalena Lake and Ameca River basins are distinctive and probably represent a different and as yet undescribed species (Kyle Piller, personal communication). Regardless of taxonomic status, X. eiseni has declined substantially over the last 25 years owing to stream channelization, water diversions, pollution, and perhaps non-native species (Domínguez-Dominguez et al. 2005b). This is despite the species being highly tolerant of environmental extremes and being considered among the hardiest of goodeids (Miller et al. 2005). Since the 1990’s, X. eiseni has disappeared from most of its Santiago, Ameca, Atotonilco, Armería, and Coahuayana basin localities, and currently persists at no more than six or seven sites. These sites are all small and localized.

Xenotoca melanosoma: Vulnerable/Stable – This species has a range generally similar to X. eiseni, although it is not found quite as far to the northwest (Miller et al. 2005). It occurs in the Santiago, Ameca, Armería, and Coahuayana river basins and the endorheic Magdalena, Atotonilco, San Marcos, Zacoalco, and Zapotlán lake basins. Since the 1960’s, it appears to have disappeared from all of the San Marcos, Zacoalco, and Zapotlán basins owing to lake drying from water diversions and perhaps also to the introduction of non-native blue tilapia, and it has been eliminated from portions of the Santiago and Coahuayana basins because of water pollution (Domínguez-Domínguez et al. 2005b). However, since the late 1990’s, distribution has remained fairly stable, and at present the species occurs at about 12 localities.

Xenotoca variata: Least Concern/Declining – This species is broadly distributed in central Mexico throughout the Lerma and upper Santiago river basins on the Pacific slope, the endorheic Lake Cuitzeo/Grande de Morelia River basin in central Mexico, and a small area of the upper Panuco River basin on the Atlantic slope (Miller et al. 2005). It is highly tolerant of pollution and habitat modifications and, along with Goodea atripinnis, still persists in areas where other goodeid species have been eliminated. Xenotoca variata is currently found at more than 30 locations throughout its historic range. Nonetheless, the species has declined in recent years, disappearing from heavily polluted areas of the Santiago and Lerma basins and from reservoir and lake habitats where the non-native largemouth black bass has become established (Lyons et al. 1998; Soto-Galera et al. 1998, 1999; Domínguez-Domínguez et al. 2005b; Mercado-Silva et al. 2006).

 

Zoogoneticus: This genus is found over a large portion of central and west-central Mexico. Until the late 1990’s, Zoogoneticus was thought to have only one species, the wide-ranging Z. quitzeoensis. Then in 1998, Z. tequila was described (Webb and Miller 1998) and in 2008, Z. quitzeoensis was split into two species, Z. quitzeoensis and Z. purepechus (Domínguez-Domínguez et al. 2008b), so now the genus contains three species.

Zoogoneticus purhepechus: Endangered/Declining – This species was recently split off from Z. quitzeoensis based on genetic and morphological differences (Domínguez-Domínguez et al. 2007, 2008b). The historical range of this species encompassed the lower Lerma, upper Santiago (including Lake Chapala), upper Ameca, and upper Armería river basins on the Pacific slope, and the endorheic Lake Magdalena, Atotonilco, San Marcos, and Sayula basins in west-central Mexico (Miller et al. 2005; Domínguez-Dominguez et al. 2008b). Lake drying, water pollution, and introductions of non-native species have eliminated Z. purhepechus from the Armeria, Atotonilco, and San Marcos basins, and possibly also the Ameca basin, and since the late 1990’s, the species has become rare in the Santiago (only a remnant population persists in Lake Chapala), Magdalena, and Sayula basins. The best remaining populations are in four small spring-fed lakes in the Duero River drainage of the lower Lerma River basin (Lyons et al. 1998; Soto-Galera et al. 1998).

Zoogoneticus quitzeoensis: Endangered/Declining – As currently defined, this species was known historically from the Angulo and Laja river drainages and Lake Yuriria in the middle Lerma River basin and throughout the endorheic Lake Cuitzeo/Grande de Morelia basin in central Mexico (Domínguez-Domínguez et al. 2007, 2008b). In recent years, Z. quitzeoensis has disappeared from the Laja River drainage, Lake Yuriria, and Lake Cuitzeo, and is greatly reduced in the Angulo and Grande de Morelia river systems owing to a combination of water pollution, habitat loss from water diversions, and introduction of non-native species (Lyons et al. 1998; Soto-Galera 1997, 1998; de la Vega-Salazar 2003a, 2005; Domínguez-Domínguez et al. 2005b, 2008a; Mercado-Silva et al. 2006). At present, seven or eight distinct populations remain, with the largest found in Lake Zacapu in the Angulo drainage and in La Mintzita Springs in the Grande de Morelia basin.

Zoogoneticus tequila: Critically Endangered/Stable? – This species, endemic to the Teuchitlán Springs in the upper Ameca River basin, was thought to be already extinct in the wild when it was first formally described in 1998 (Webb and Miller 1998), and many scientists and aquarists continue to believe that no wild populations exist (Miller et al. 2005). However, in 2000, a tiny remnant wild population was discovered in a small and isolated area of the Teuchitlán Springs (de la Vega-Salazar 2003b), and the species continues to persist there (Domínguez-Domínguez et al. 2005b, 2008a). Unfortunately, this population is so small that it has become inbred and its long-term viability is in doubt (Bailey et al. 2007). Several captive populations exist, but those that have been checked also appear to be inbred.

 

 

Conclusions and Implications for Aquarists

The Mexican goodeids are at a crossroads. Once the most diverse, widespread, and numerous group of fishes in central Mexico, they now have been reduced to only a shadow of their former distribution and abundance. If they are to survive the 21st century, major conservation initiatives must be undertaken. The remaining wild populations must be protected, and, where practical, lost populations should be restored. Aquarists can play an important role in both protection and restoration. They can support and promote Mexican and international groups and projects that focus on the conservation of freshwater habitats and native diversity within the range of the goodeids. They can draw on their experiences keeping goodeids and provide scientists and conservationists with essential information on goodeid biology that cannot be determined from remaining wild populations. And perhaps most importantly, aquarists can maintain captive populations of goodeids to provide a source for re-introductions in restored habitat, to supply specimens for scientific study and public education, and to prevent species from becoming totally extinct if they are lost from the wild. Only a few educational and scientific institutions maintain goodeids, and a diverse worldwide network of aquarists can help insure that goodeid species do not disappear from captivity.

Literature           Table