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The Cuatro Ciénegas valley is home to 16 species of native fishes, 9 of which are endemic. The threat of habitat reduction, degradation, and introductions of exotic species looms over much of the valley and is a constant threat to the continued existence of these species. Understanding patterns of desiccation in the valley can be important for managing water use in the valley and understanding aquifer dynamics. We retook photographs from 12 sites for which historic photographs existed. Some of these photographs are from as far back as the 1920’s. By comparing historic to modern photographs we will discuss drying in the Cuatro Ciénegas Basin. It appears that drying has been mainly limited to habitats on the perimeter of the valley while habitats in the center of the valley, at lower altitudes, remain similar to historic conditions. Compared to at least three sites just outside the valley, many sites in Cuatro Ciénegas still remain relatively pristine. This contribution was supported in part by a grant from the Nature Conservancy to Hendrickson, Marks and Francisco García de León, and made possible by INE permits to García de León.

The ictalurid genus Prietella was described from a single locality in northern México (Coahuila) in 1954, and until very recently went largely unstudied. Cave explorers have recently uncovered new localities and a second species much farther to the south (México: Tamaulipas). Our team visited over 50 sites, including all of the previously known sites possible, and explored many new sites, expanding the known range of Prietella and describing their habitat. We identified geological units and mapped caves, identified associated troglobitic invertebrates, estimated population sizes and measured water chemistry parameters. We also comment on laboratory diet, parasites, sensory biology, behavior (such as jaw locking and periods of inactivity), reproduction and systematics based on preliminary genetic data. Prietella phreatophila is listed as endangered, and due to the recent discovery of many more sites (formerly documented from three localities, now known from twelve sites, though some are hydrologically connected) we recommend threatened status, with careful attention to growing threats such as over pumping and contamination of the aquifer it lives in. Should these patterns continue unchecked, re-listing this species as endangered may be called for. Prietella lundbergi was also described from one site but is now known from two, though it is quite rare at both (only five specimens have ever been seen). P. lundbergi was described after the most recent revision of the Mexican endangered species list and should probably be considered as endangered.

The mission of the Desert Fishes Council is to preserve the biological integrity of North America’s desert aquatic ecosystems and their associated life forms, to hold symposia to report related research and management endeavors, and to effect rapid dissemination of information concerning activities of the Council and its members.

Abstract of paper presented at Annual Meeting of the Society for Integrative and Comparative Biology, January 02-06, 2002, Anaheim, California, USA – The basin of Cuatro Cienegas, with over 200 springs and pools, lies in the Chihuahuan desert of northern Mexico. The area is a high priority conservation site with many endemic fishes and mollusks. Although geographically isolated, the basin’s fauna is threatened by invading species. Stable isotope studies using 13C and 15N revealed dietary overlap between juveniles of the endemic cichlid, Herichthys minckleyi, and the invasive cichlid, Hemichromis guttatus. We conducted a field enclosure experiment to examine this interaction using growth rates as the dependent variable. Results showed H. minckleyi juveniles lost weight in the presence of H. guttatus. In contrast, H. guttatus gained weight in the presence of H. minckleyi indicating that H. guttatus could out compete H. minckleyi juveniles. These results provide strong evidence that juvenile H. minckleyi found in habitats with H. guttatus will be negatively affected potentially leading to increased juvenile mortality for H. minckleyi.

Polymorphism in feeding structure could be rare because it represents an ephemeral and transitional stage in speciation. Alternatively, intraspecific morphological specialization may be latent in many species and only arise in exceptional ecological settings due to distinct functional demands prey place on predators. In order to unravel these hypotheses, we examined diet specialization in the trophically polymorphic cichlid fish Herichtys minckleyi using gut analysis and stable isotopes obtained from fish from eight populations in Cuatro Cienegas in Northeastern Mexico. We found papilliform pharyngeal morphs ate a greater percentage of plants and arthropods compared to molariform morphs. Although snail shell constituted some proportion of the gut contents of all jaw types, papilliform morphs are not often crushing snails. Approximately 90% of molariform morph guts contained crushed snails and their isotope signatures differed significantly from papilliform morphs. Individuals with intermediate pharyngeal morphologies frequently crushed snails and have stable isotope values between the molariform and papilliform morphs indicating their diets reflect their intermediate dentition. Using the snail opercula found in the guts, we estimated both the number of snails eaten and force used by individual H. minckleyi to crush snails. By quantifying the condition of amphipods, we also assessed the shredding abilities of the pharyngeal morphs. The hardness of the shells of snails inhabiting Cuatro Cienegas will be contrasted with those of other molluscs. Finally, the estimated ontogenetic pharyngeal jaw crushing abilities of H. minckleyi will be compared to other molluscivores.

The Rio Fuerte drains 33,835 km2.of the Sierra Madre Occidental of the Mexican states of Chihuahua, Sinaloa, Durango, and Sonora. Its tributaries pass through Barranca del Cobre (Copper Canyon) as they drop from headwaters as high as 2,808 m above sea level to the Mar de Cortes (Gulf of California). Its headwaters interdigitate closely with east-flowing tributaries of the Rio Conchos, an important tributary of the Rio Bravo (Grande), and interior drainages of Chihuahua and Durango, such as the Rio Nazas. The Fuerte shares its fish fauna with these neighboring drainages, and has no endemics. Northernmost tributaries are relatively arid, but southern tributaries drain sub-tropical areas with much higher rainfall. Dams and diversions now block movements of many marine fish species that used to move far upstream, and more are in construction or planned. Large river fish habitats at lower elevations have been converted almost entirely into canals and the natural mainstream channel now carries only minimal or highly modified discharges, often contaminated by agricultural runoff. At higher elevations, fish habitats have been severely impacted by logging and grazing. Logging development continues, recently expanding from traditional conifers to lower-elevation oaks. Exotic fishes have had, or surely will have, broad impacts on the native fauna through predation, competition and hybridization. Tilapias from Africa are widely established now, as are several centrarchids that will undoubtedly impact on the native cichlid (Cichlasoma beani), cyprinids, catostomids, poeciliids, and others. While not well studied taxonomically, the basin’s native catfish, closely related to Ictalurus pricei, is now broadly hybridizing with introduced channel catfish (I. punctatus). At higher elevations, the beautiful native Mexican golden trout is very likely to hybridize with rainbow trout being widely introduced for fish culture. El Rio Fuerte drena 33,835 km2 de la Sierra Madre Occidental en los estados de Chihuahua, Sinaloa, Durango y Sonora. Sus tributarios fluyen a traves de la Barranca de! Cobre (Copper Canyon) y caen desde las cabeceras de 2,808 m sobre el nivel del mar hacia el Mar de Cortes (Gulf of California). Sus cabeceras interdigitan cercanamente con los tributarios de flujo este del Rio Conchos, un importante tributario del Rio Bravo (Grande) y drenajes interiores de Chihuahua y Durango como el Rio Nazas. El Fuerte comparte su fauna de peces con estos drenajes vecinos y no presenta endemicos. Los tributarios norteños son relativamente aridos, pero los tributarios sureños drenan areas subtropicales con mayor regimen de lluvias. Las presas y canales, que bloquean ahora el movimiento de muchas especies de peces marinos que lo usaban para remontar el rio, siguen en construcción y planeación. Los habitats de peces de rios grandes en bajas elevaciones han sido convertidos en canales y el canal principal natural ahora mantiene descargas minimas o altamente modificadas, frecuentemente contaminadas por desechos de la agricultura. A grandes elevaciones, los habitat de los peces han sido impactados severamente por la tala y el pastoreo. Los desarrollo madereros continuan y recientemente se han expandido de las tradicionales coniferas a los encinos de mas baja elevaci6n. Los peces exóticos tienen o seguramente tendran grandes impactos sobre los peces nativos a traves de la depredación, competencia e hibridación. Las tilapias de Africa estan ahora ampliamente establecidas al igual que varios centrarquidos, que indudablemente impactan sobre el ciclido nativo (Cich/asona beani), ciprinidos, catost6midos, pecilidos y otros. Aunque no esta bien estudiado taxonomicamente, el bagre nativo de la cuenca, cercanamente relacionado a Ictalurus pricei, esta ahora hibridizandose ampliamente con el bagre de canal introducido. A grandes elevaciones, la hermosa trucha dorada Mexicana nativa, es muy posible que hibridice con la trucha arcoiris, que ha sido ampliamente introducida como pez de cultivo.

A grant has been awarded to Dr. Richard L. Mayden at Saint Louis University to conduct field and laboratory research in collaboration with other USA scientists and several scientists from Mexico on the environmental status, distribution, conservation and genetics of native trout populations of Mexico. While biologists have been aware of the existence of native trout in Mexico for over a century, they have received little study. Beginning in the mid-1990’s a group of ichthyologists and conservation biologists from both Mexico and USA jointly formed an international alliance, Truchas Mexicanas, to better understand the native trout of the Sierra Madre Occidental. Through these efforts, scientists have discovered previously unknown trout species restricted to Mexico and introduced (non-native) populations of rainbow trout. The existence of these non-native rainbow trout originating from streams in the US and Canada in the ranges of the unique Mexican trout species is a significant threat to the future existence of native species. Rainbow trout are known to displace native trout species through competition or genetically “swamp out” their gene pools through aggressive hybridization. Other native populations of trout are also predicted to occur in the upper Rio Conchos; these populations are predicted to also be in danger from habitat destruction and introductions of rainbow trout. In this study we will inventory many river systems of the sierras for native and introduced trout species, including the upper Conchos River system. Genetic samples will be examined from all of these populations to evaluate genetic variability of native species and determine if any native populations are compromised genetically through hybridization with introduced rainbow trout. This research supports the development of an international alliance investigating native trout populations of Mexico and southwestern United States. Trout species are important game and forage species for human populations, constituting a major element of diets in some regions. Trout fisheries are also very important economic elements to some regions as trout are highly prized sport fish species. Understanding native trout species diversity in Mexico and its conservation and maintenance in these streams has a major impact on both fisheries and economic areas. Mexican trout species are the southern-most trout and are adapted to theses unique ecosystems. Introductions of non-native rainbow trouts will seriously jeopardize these adapted populations and lead to their extirpation from the region. This will have serious sociological and economic impacts for the native people of the region.

The mission of the Desert Fishes Council is to preserve the biological integrity of North America’s desert aquatic ecosystems and their associated life forms, to hold symposia to report related research and management endeavors, and to effect rapid dissemination of information concerning activities of the Council and its members.

Resource polymorphisms, or morphological variations related to resource use, are common in fishes and are thought to be a possible step in speciation. This study experimentally tests the hypothesis that fitness (as estimated by growth rates) is increased by the presence of multiple trophic morphotypes (or morphs) within a population. Cage experiments were used to quantify the intraspecific competitive interactions between morphs of the polymorphic cichlid Herichthys minckleyi in Cuatro Ciénegas, México. Results suggest that competition is reduced between morphs in mixed-morph treatments relative to equal-density single-morph treatments. Field studies revealed that the morphs feed in different microhabitats and use different feeding behaviors within these microhabitats. These results suggest that the polymorphism is maintained in the population because it decreases competition between the morphs, and that differences in feeding behavior facilitate resource partitioning.

While biologists have been aware of the existence of native Mexican trouts for over a century, they have received little study. The few early studies that did much more than mention their existence began in the 1930s and continued into the early 1960s, focusing primarily on distributional surveys and taxonomic analyses. Starting in the 1980s the Baja California rainbow trout became the subject of more detailed studies, but very little remains known of mainland trouts of the Sierra Madre Occidental. We review earlier studies and report on our own collections and observations made between 1975 and 2000. We present newly discovered historical evidence that leads us to conclude that a lost” cutthroat trout, a lineage not previously known from Mexico, was collected more than a century ago from headwaters of the R¡o Conchos (a major tributary of the Rio Grande (= R¡o Bravo)), a basin not previously considered to harbor a native trout. We review the last century of regional natural resource management and discuss our own observations of trout habitats. Impacts of logging, road building and overgrazing are widespread and expanding. Many streams suffer from heavy erosion, siltation and contamination, and though long-term hydrologic data are generally not available, there is evidence of decreased discharge in many streams. These problems appear related to region-wide land management practices as well as recent regional drought. Trout culture operations using exotic rainbow trout have rapidly proliferated throughout the region, threatening genetic introgression and/or competition with native forms and predation on them. Knowledge of distribution, abundance, relationships and taxonomy, not to mention ecology and population biology, of native trouts of the Sierra Madre Occidental remains inadequate. Vast areas of most mainland drainages are still unexplored by fish collectors, and even rudimentary information regarding basic biology, ecology and population structure of stocks remains lacking. Concentrated exploration, research and management of this long overlooked and undervalued resource are all urgently needed. The history of natural resources exploitation that placed so many native trouts of the western United States on threatened and endangered species lists is repeating itself in the Sierra Madre Occidental. Without concerted action and development of region-wide socio-economic solutions for current, largely non-sustainable resource management practices, native Mexican trout gene pools will soon be in grave danger of extinction.

The mission of the Desert Fishes Council is to preserve the biological integrity of North America’s desert aquatic ecosystems and their associated life forms, to hold symposia to report related research and management endeavors, and to effect rapid dissemination of information concerning activities of the Council and its members.

The mission of the Desert Fishes Council is to preserve the biological integrity of North America’s desert aquatic ecosystems and their associated life forms, to hold symposia to report related research and management endeavors, and to effect rapid dissemination of information concerning activities of the Council and its members.

The Mexican Neovolcanic Plateau sharply divides the vertebrate fauna of Mesoamerica where the climate of both the neotropics 12 and temperate North America gradually blend. Only a few vertebrate groups such as the Heroine cichlids, distributed from South 13 America to the Rio Grande in North America, are found both north and south of the Neovolcanic Plateau. To better understand the 14 geography and temporal diversification of cichlids at this geologic boundary, we used mitochondrial DNA sequences of the cy- 15 tochrome b (cyt b) gene to reconstruct the relationships of 52 of the approximately 80 species of Heroine cichlids in Mesoamerica. 16 Our analysis suggests several cichlids in South America should be considered as part of the Mesoamerican Heroine clade because 17 they and the cichlids north of the Isthmus of Panama are clearly supported as monophyletic with respect to all other Neotropical 18 cichlids. We also recovered a group containing species in Paratheraps + Paraneetroplus+ Vieja as the sister clade to Herichthys. 19 Herichthys is the only cichlid clade north of the Mexican Plateau and it is monophyletic. Non-parametric rate smoothing of cichlid 20 cyt b sequence resulted in an estimated divergence time of approximately 6 million years for Herichthys. This temporal diversifi- 21 cation is concordant with divergence times estimated for anurans in the genus Bufo, a group that exhibits a similar geographic 22 distribution. Our results indicate the 5-million-year-old extension of the Mexican Neovolcanic Plateau to the Gulf Coast of Mexico 23 has strongly influenced the current transition between the vertebrate faunas of the Neotropics and Nearctic

Nymphophilus minckleyi is a hydrobiid snail endemic to the freshwater spring ecosystem of Cuatro Ciénegas, Mexico. We used seven allozyme loci to examine the genetic substructure of N. minckleyi from 14 sites (subpopulations) in the basin and to test the hypothesis that spring pools in Cuatro Ciénegas are separated into seven hydrologically distinct drainages. Hierarchical F-statistics suggest significant population structure exists among the fourteen populations but not among the seven proposed drainages. Cluster analysis of Nei’s genetic distance did not show populations grouping according to drainages, although it did reveal alternative clusters. We found two distinct morphotypes that were supported as genetically distinct groups by the allozyme data. Genetic studies of vagile species in desert spring ecosystems can be used to reveal hydrologic connections and identify genetically unique sub-populations.

A new family (Lacantuniidae), genus and species of catfish, Lacantunia enigmatica, is described from the Río Usumacinta basin of Chiapas, México. This odd siluriform is diagnosed by five distinctively autapomorphic and anatomically complex structures. The fifth (last) infraorbital bone is relatively large, anteriorly convex and remote from a prominent sphenotic process. The lateral margin of the frontal, lateral ethmoid and sphenotic bones are thick at the origins of much enlarged adductor mandibulae and levator arcus palatini muscles; otherwise the skull roof is constricted and flat. One pair of cone-shaped “pseudo-pharyngobranchial” bones is present at the anterior tips of enlarged cartilages medial to the first epibranchial. A hypertrophied, axe-shaped uncinate process emerges dorsally from the third epibranchial. The gas bladder has paired spherical, unencapsulated diverticulae protruding from its anterodorsal wall. Lacantunia enigmatica cannot be placed within or as a basal sister lineage to any known catfish family or multifamily clade except Siluroidei. This species may represent an ancient group, perhaps of early Tertiary age or older, and it adds another biogeographic puzzle to the historically complex Mesoamerican biota.

With an origin dating back 400 million years, fishes represent the most ancient group of vertebrates (Helfman et al. 1997). They are also the most diverse, with more than 25,000 species. Of the more than 2200 species known from Mexico, about 500 live in freshwater. The Mexican Official Norm NOM-059-ECOL-2001 lists only 186 fish species among the 1515 vertebrates “At Risk” in Mexico (SEMARNAT 2002; see chapter 4). Fishes thus account for only 12.3% of all listed species in Mexico, compared to 30.8% for reptiles, 24.8% birds, and 19.5% mammals. Why are so few fishes listed in Mexico? The answer probably has little to do with actual conservation status and more to do with other factors. First, the great taxonomic diversity of fishes renders any comprehensive evaluation of their conservation status quite daunting. Not only are fishes more than half of all vertebrate species, but new species continue to be described every year (Helfman et al. 1997). Because fishes live only in water, they are more difficult to observe than are most other vertebrates. Finally, fishes show a high degree of intraspecific phenotypic variation that makes them highly sensitive to environmental factors and often difficult to identify (Allendorf et al. 1987; Allendorf 1988). Fishes are important to humans because they represent an important source of food. Their commercial and recreational value has led to fish farming on an industrial scale, both for easy exploitation and as a means to recover overharvested natural populations. Scientific interest in fishes is also considerable. Those species easy to manage in captivity can be used in laboratory experiments. Additionally, freshwater fishes in particular can be used as biogeographic indicators, contributing important information to our understanding of the history of river basins and serving as indicators of aquatic ecosystem health. Though their aquatic habitats perhaps make wild fish populations more difficult to study than terrestrial organisms, they clearly deserve greater emphasis in the field of biological conservation. The northern part of Mexico harbors 3 aquatic ecoregions known as the Sonoran, ChihuahuanPotosian, and Tamaulipan regions (ContrerasBalderas 1969). The Tamaulipan ecoregion is located between the Sierra Madre Oriental and the Gulf of Mexico, within the Mexican states of Coahuila, Nuevo Leon, and Tamaulipas (CONABIO 2000); the last of these states is the focus of this chapter. To the north, Tamaulipas is bounded by the Rio Grande (Rio Bravo), which marks the border with Texas. To the west, Tamaulipas is bounded by the Mexican states of Nuevo Leon and San Luis Potosi, to the east by the Gulf of Mexico, and to the south by the states of Veracruz and San Luis Potosi (fig. 7.1). The geomorphology of watersheds influences species richness (Eadie et al. 1986). For example, river discharge is a direct measure of availability of habitat for freshwater fishes (Livingstone et al. Patterns of Species Diversity and Ecological Importance of Natural Ecosystems 1982), and there is a positive correlation between species richness and surface area of a river basin (Horwitz 1978). Thus, anthropogenic alterations of a watershed can drastically reduce its associated biological diversity (Sheldon 1987). Decreases in total habitat area and habitat fragmentation (typically a result of dams) occur conjunctively, reducing not only the size of many populations but also the potential for dispersal and genetic flow (Frankham et al. 2001). Additionally, diversion canals linking once separate waterways, and the introduction of exotic species, are both leading to homogenization of aquatic faunas (Sheldon 1988). Due to the rapid increase in hu.man populations, northern Mexico has experienced major, humaninduced alterations and fragmentation of its watersheds and associated changes in the distribution of taxa and loss of biodiversity (Contreras-Balderas 1978). Clearly, any conservation effort requires an inventory of the ichthyofauna using a taxonomic and biogeographic approach, focusing on documenting and maintaining overall biodiversity, but also including the rare and endangered species. The specific objectives of the study described in this chapter were to evaluate the diversity of freshwater fishes in Tamaulipas, to characterize each watershed and analyze the status of its ichthyofauna, and to determine the level of anthropogenic impact on freshwater fish communities statewide. We begin with a description of the watersheds of Tamaulipas, then present a synthesis of the state of knowledge of taxonomy, biology, genetics, evolution, exploitation, and conservation of fishes in Tamaulipas and provide the first list of freshwater fishes assembled for the state.

A new family (Lacantuniidae), genus and species of catfish, Lacantunia enigmatica, is described from the Río Usumacinta basin of Chiapas, México. This odd siluriform is diagnosed by five distinctively autapomorphic and anatomically complex structures. The fifth (last) infraorbital bone is relatively large, anteriorly convex and remote from a prominent sphenotic process. The lateral margin of the frontal, lateral ethmoid and sphenotic bones are thick at the origins of much enlarged adductor mandibulae and levator arcus palatini muscles; otherwise the skull roof is constricted and flat. One pair of cone-shaped “pseudo-pharyngobranchial” bones is present at the anterior tips of enlarged cartilages medial to the first epibranchial. A hypertrophied, axe-shaped uncinate process emerges dorsally from the third epibranchial. The gas bladder has paired spherical, unencapsulated diverticulae protruding from its anterodorsal wall. Lacantunia enigmatica cannot be placed within or as a basal sister lineage to any known catfish family or multifamily clade except Siluroidei. This species may represent an ancient group, perhaps of early Tertiary age or older, and it adds another biogeographic puzzle to the historically complex Mesoamerican biota.

Herichthys minckleyi Kornfield & Taylor 1983 is an endangered, trophically polymorphic cichlid endemic to the Cuatro Ciénegas basin of Coahuila, Mexico. A “molariform” morph has stout pharyngeal teeth while a “papilliform” morph has numerous fine pharyngeal teeth. Individuals with intermediate pharyngeal dentition also exist, as does yet another morph, called the “piscivore,” that has a comparatively more fusiform body than do “normal-bodied” individuals. Previous studies indicated that morphs utilize different food sources, thus suggesting morph-specific spatial segregation would be likely since food resource availability is spatially heterogeneous. We present data from an observational study of all morphs (but focusing on the 3 most common, normal-bodied ones – molariform, papilliform and intermediate) in a single spring pool, Poza Mojarral Oeste. We analyzed morph distribution in relation to habitat types, and document morph-specific differences in feeding behavior. Habitat partitioning on both spatial and temporal axes was also investigated. Habitat use by each molariform, papilliform, and intermediate pharyngeal morphs was found to be non-random. Morphs differed in habitat use, albeit with considerable overlap. Strong segregation among morphs was not detected in any season or time of day, but habitat use patterns varied seasonally within each morph and were consistently different among morphs. Morphs of this species displayed a variety of feeding behaviors, but in general all behave as feeding generalists. This endangered species may prove more difficult to manage than are other, non-polymorphic species. It is clearly important to manage not only for the maintenance of the species, but also for maintenance of its different morphs, which our study indicates may each require different mixes of habitat types⬚. We thus hypothesize that any changes in habitat heterogeneity will lead to altered proportions of the different morphs of the species.⬚

We studied how pharyngeal jaw morphology influences feeding performance and prey use in the trophically polymorphic cichlid fish Herichthys minckleyi. In this species, the pharyngeal jaw exhibits two discrete morphologies. “Molariforms” possess robust jaw structure with flattened teeth and enlarged muscles, and “papilliforms” exhibit more gracile jaws, pointed teeth, and smaller muscles. The threefold difference in molariform and papilliform pharyngeal muscle mass found in an ontogenetic series of individuals (Range: 65 mm to 146 mm) support the hypothesis that the morphotypes differ in crushing force used to process prey. For both morphotypes, we also tested for tradeoffs in handling time and the ability to process several types of prey that occur in H. minckleyi’s native habitat, Cuatro Ciƒ\_snegas. Unexpectedly, handling time on plants and arthropods was only slightly different between morphotypes. However, papilliforms consistently shredded plants more finely than molariforms, while only molariforms appeared capable of crushing snails. We inferred molariforms routinely employed their maximum force producing capabilities in the wild to crush the exceptionally hard snails endemic to Cuatro Ciƒ\_snegas. Comparisons with other molluskivorous fish suggested that the amount of hard-shelled prey H. minckleyi ingests is not unusual, but the mass of its pharyngeal musculature and the force used to crush snails is unparalleled.

Synopsis We analyzed feeding behavior of individuals of Herichthys minckleyi, the Cuatro Ciénegas cichlid, under laboratory conditions and freely behaving in their natural environment using high-speed video imaging. In a multivariate analysis of suction feeding behaviors there was no clear grouping of feeding events based on the environment, which suggests that most of the variability in the data was unrelated to differences between lab and field behaviors. In fact, the variability within an environment was far greater than the variability between the two environments. These results suggest that laboratory studies can accurately describe the kinematics of behaviors seen in the field. However, although lab based studies can quantify behaviors seen in the field, natural habitats are complex and provide individuals with the opportunity to exploit a wide range of food types and microhabitats, which may elicit behaviors not observed in the laboratory. However, feeding behaviors observed in the lab are representative of frequently used feeding behaviors in the field, at least for this species. Thus, we suggest that laboratory studies of feeding behavior, particularly those that test biomechanical or performance-based hypotheses can be extrapolated to natural environments.

The Northwestern Sierra Madre Occidental of Mexico is a rugged mountain range covering portions of Sonora, Chihuahua, Durango and Sinaloa, and is drained by multiple Pacific Slope Rivers to the west and the Casas Grandes, Conchos, and Nazas to the east. The overall area is topographically, climatically and biotically diverse, ranging from endorheic basins (Casas Grandes) to mountainous areas elevations up to 3348 m, average mean temperatures from 10-20°C and precipitation from 250- 1100 mm/yr. The region is also geological complex that, combined with these other variables, provides a great diversity of both aquatic and terrestrial habitats conducive to both biotic endemicity and diversity. The overall diversity of the region has contribiited to the recent listing of this region by Conservation International as one of six new high-priority biodiversity hotspots. Our understanding of the aquatic and terrestrial biodiversity of this region, however, is poor and in urgent need of rapid investigation by collaborative communities. The combination of an incredibly rugged landscape, drug and bandit activities and indigenous peoples that have not always been welcoming to visitors has resulted in a general paucity of roads in the region, and the lack of access has limited inventory studies. Recently, however, access to the region has changed dramatically and many of the areas are now accessible enough for logging, mining, and agriculture practices, all exerting extreme pressures in some areas on the biodiversity. In addition to human-induced changes to these diverse ecosystems, impacts of invasive aquatic species are becoming more and more apparent, and the potential for severely reducing population sizes of species or their extirpation or extinction is real. While several invasive or exotic species are identified as potentially destructive to these communities, the exotic Rainbow Trout (Oncorhynchus mykiss) that is derived from hatcheries or culture facilities within the region represents one of the most critical threats to the aquatic and semi-aquatic biodiversity. The native trout of mainland Mexico represent the southern- most salmonids, and are at imminent risk of introgression and/or replacement by feral Rainbow Trout, Oncorhynchus mykiss. Our recent survey efforts have expanded the known diversity and ranges of each of several distinct forms, which we feel represent valid species. We discuss our discovery of multiple new species from the Sierra Madre Occidental and focus on a new species of trout restricted to the upper Conchos drainage, the first native species of Oncorhynchus known to occupy the Atlantic Slope in Mexico. Many of these taxa are restricted to small areas of intact habitat in headwater areas of high-elevation streams, and are at risk from a suite of human-associated perturbations, emerging diseases, and introduced species. These fishes occupy unique habitats, and represent a diverse portion of the Mexican montane ichthyofauna. The habitats on which they depend support a wide range of other aquatic organisms, most of which are grossly understudied. The discovery of the Conchos Trout derived primarily by GARP niche modeling of a subset of localities of previously sampled undescribed native Mexican trout, provides only a snapshot of the biodiversity awaiting to be discovered in this region. The rugged landscape of the Sierra Madre Occidental simply precludes routine sampling at easily accesible locations of streams and most sampling locations require time-intensive access. In an effort to rapidly assess the biodiversity of rivers of this region we employed this method to aid in predicting the most suitable and highly probable Mexican trout niches in the region. This method offered highly efficient and powerful results that not only predicted the occurrence of a previously unknown trout in the upper Rio Conchos but also provided excellent predictions of available habitats in drainages where previously unknown trout have been discovered by the Truchas Mexicanas team in the last nine years. Multiple threats exist to the biodiversity of the northern Sierra Madre Occidental, including uncontrolled introductions of exotic and invasive species, emerging diseases such as whirling disease, Myxobolus cerebralis, infectious pancreatic necrosis (IPN), iridioviruses and pathogenic water mold, Saprolegnia ferax, land-use practices leading to habitat degradation via overgrazing, logging, deforestation and road construction, increasing human population growth, over-fishing or overharvesting of aquatic resources and global climate cliange reducing surface and ground water in the area and creating environments more conducive to the spread of invasive species, congregated and dense human populations, and emerging diseases. Immediate actions need to be developed to aid in public education as to the threats to these ecosystems, protection of areas, assessment of diversity, and sustainable development throughout the region that incorporates a likely highly successful ecotourism system for the region.

A complex of little-studied catfishes of the genus ⬚Ictalurus⬚ is native to Pacific drainages of the Sierra Madre Occidental and interior drainages of Northwest Mexico. Its only described member, ⬚Ictalurus pricei⬚, is protected by the Mexican and US governments and given varied conservation status by diverse other conservation organizations. We contribute new data and a review of previous work to partially rectify prior inadquacies of genetic and conservation status information on the complex. Sequence data for the cytochrome b (⬚cytb⬚) and 12S ribosomal (⬚12SrRNA⬚) mitochondrial genes provide new diagnostic molecular characters for ⬚I. pricei⬚ and both genes display intra-specific variation. The only ⬚I. pricei⬚ specimens we could obtain, however, despite extensive field collection efforts, were from a captive broodstock established starting 20 years ago for conservation purposes. We provide basic, previously unpublished information about the history and, unfortunately, recent apparent demise of that captive stock. Non-native catfishes are widely introduced throughout the range of the ⬚pricei⬚ complex and, along with habitat degradation, represent a significant, but still very little-studied threat to its genetic integrity and persistence. Conservation of the Yaqui catfish is clearly a complicated issue with much remaining to be learned, but it is clear that current levels of protection do not adequately reflect its critical conservation plight and management efforts to date have failed to provide appropriate, long-term conservation actions and much-needed research.

México is the southernmost country in North America, and extends into Central America, south of the Isthmus of Tehuantepec. The northern half of México is located on the Temperate belt and is arid in character (Nearctic), while the rest is within the Tropical belt (Neotropical). Climate varies from extremely temperate desert in the north, to tropical humid in the south. México has more than 500 freshwater fish species, about 271 of them country endemics, and approximately 48 endemics from binational basins. There are still some 30–40 fish species not yet described. There are 563 fish species colonizing coastal flood plain species. In addition to the numbers of colonizing fishes, the burden of introduced exotics has also been growing. In 1904, only 4 species were recognized as exotics; by 1997 the number had increased to 94, and by 2008 to 115. The main fish collections in Mexico are at IPN, UNAM, and UANL and are the most representative, being national in scope, although concentrated in the tropics, central region, and general in coverage, respectively. The decline of the native fish fauna has been in focus in recent years, usually as trend-in-time comparisons, where the loss of native forms and increase of exotics and/or colonizer species is evident in many basins, mainly in Río Balsas, Río Grande, and Río Lerma-Santiago. As a result, the numbers of species reported at some degree of risk have been increasing also, from 17 in 1963 to 192 in 2005. The trends in colonizers, exotics, and species at risk among Mexican fishes are parallel. The Index of Biological Integrity (IBI), in either its geographical, or historical form (IBIh), has been applied to the Rio Grande/Río Bravo basin, USA and México. IBIh values go between 0–91 (average 31). Alien species are regarded as detrimental. Overall, the IBI trends have been similar in all regions, starting from 70–95% in upper reaches, decreasing to less than 0–35% in the lower reaches of West central basins, and then down to 15% or less near the Lower Rio Grande delta. Several alien species of plecos have been recognized in the rivers Balsas, Grijalva-Río Usumacinta complex, and, also, one in the Rio Grande. Mexican rivers are notoriously dewatered in the northern half of the country. Until 1962, the Rio Grande had an average runoff of 12,000+ millions of cubic meters/year; however by 2002 it was less than 2% of that value. The river went nearly dry along the Big Bend region and was dry for months in the delta region, both in 2002 and 2004. The Rio Grande is mostly dry north of the Río Conchos junction, its main Mexican tributary, and other tributaries provide now between 1% (Río San Juan) and 20% (Río Conchos) of pre-1960 runoff. A modified Index of Biological Integrity for Rio Grande resulted in grades from 70 to 95% of the baseline in upper reaches, less than 35% in lower reaches, to less than 15% near the coast. The Texan version of the IBI was not representative as it suppresses data on euryhaline fishes. The reports of total toxics were masked, since the sum should have included both organics and heavy metals exceeding USA regulations to the total count, but only one of the two was included.

This is the third compilation of imperiled (i.e., endangered, threatened, vulnerable) plus extinct freshwater and diadromous fishes of North America prepared by the American Fisheries Society’s Endangered Species Committee. Since the last revision in 1989, imperilment of inland fishes has increased substantially. This list includes 700 extant taxa representing 133 genera and 36 families, a 92% increase over the 364 listed in 1989. The increase reflects the addition of distinct populations, previously non-imperiled fishes, and recently described or discovered taxa. Approximately 39% of described fish species of the continent are imperiled. There are 230 vulnerable, 190 threatened, and 280 endangered extant taxa, and 61 taxa presumed extinct or extirpated from nature. Of those that were imperiled in 1989, most (89%) are the same or worse in conservation status; only 6% have improved in status, and 5% were delisted for various reasons. Habitat degradation and nonindigenous species are the main threats to at-risk fishes, many of which are restricted to small ranges. Documenting the diversity and status of rare fishes is a critical step in identifying and implementing appropriate actions necessary for their protection and management.

The variation and composition of Mexican wild trout mitochondrial DNA haplotypes throughout northwestern Mexico was determined by means of polymerase chain reaction-restriction fragment polymorphism analysis (PCR-RFLP), of one region of mitochondrial DNA between cytochrome b and the D-loop. This analysis was based on 261 specimens taken in 12 basins and four hatcheries from northwestern Mexico. From 23 haplotypes, 15 wild trout haplotypes were identified and classified in four groups: (1) one restricted to Nelson’s trout (Oncorhynchus mykiss nelsoni), (2) four restricted to R¡o Mayo and R¡oYaqui trout (O. mykiss sspp.), (3) six to Mexican golden trout (O. chrysogaster) with two subgroups, and (4) one exclusive to R¡o Piaxtla trout. Distributions of native haplotypes broadly overlap the distribution of non-native hatchery rainbow trout reflecting the historical management of introductions of exotic rainbow trout and the artificial transference of these trout among basins.

The evolutionary viability of an endangered species depends upon gene flow among subpopulations and the degree of habitat patch connectivity. Contrasting population connectivity over ecological and evolutionary timescales may provide novel insight into what maintains genetic diversity within threatened species. We employed this integrative approach to evaluating dispersal in the critically endangered Coahuilan box turtle (Terrapene coahuila) that inhabits isolated wetlands in the desert-spring ecosystem of Cuatro Ciénegas, Mexico. Recent wetland habitat loss has altered the spatial distribution and connectivity of habitat patches; and we therefore predicted that T. coahuila would exhibit limited movement relative to estimates of historic gene flow. To evaluate contemporary dispersal patterns, we employed mark-recapture techniques at both local (wetland complex) and regional (inter-complex) spatial scales. Gene flow estimates were obtained by surveying genetic variation at nine microsatellite loci in seven subpopulations located across the species’ geographic range. The mark-recapture results at the local spatial scale reveal frequent movement among wetlands that was unaffected by inter-wetland distance. At the regional spatial scale, dispersal events were relatively less frequent between wetland complexes. The complementary analysis of population genetic substructure indicates strong historic gene flow (global FST = 0.01). However, a relationship of genetic isolation by distance across the geographic range suggests that dispersal limitation exists at the regional scale. Our approach of contrasting direct and indirect estimates of dispersal at multiple spatial scales in T. coahuila conveys a sustainable evolutionary trajectory of the species pending preservation of threatened wetland habitats and a range-wide network of corridors.

Sprawling across a cactus-studded valley in México’s Chihuahuan Desert is a place like no other on the planet. . It’s called Cuatrociénegas, and it is a crunchy expanse of land isolated in a basin ringed by mountains like salt on the rim of a margarita glass. The seemingly dry, desert area, however, is best known for its life-giving waters—pools, wetlands and rivers filled to the brim with an amazing assortment of unique species. “This is an incredibly diverse area for this part of the world, with more endemic species per area than the Galápagos Islands,” says Dean Hendrickson, curator of ichthyology at the Texas Natural Science Center. But Cuatrociénegas is not immune to change, and its rare ecosystems are under increasing pressure from climate change, invasive species and agriculture. Hendrickson, who has been visiting the area since 1979, now finds himself working with others to forge a sustainable future for the region. “My vision is to get a big interdisciplinary, international project going and try to find solutions that we can propose to the local community,” he says. He has established a permanent research station in town, and he hopes this will encourage more researchers from other fields to begin projects there. “There are very complex issues here that go way beyond simple biology and conservation and get into sociology and economics,” he says.

Researchers at the University of Texas at Austin are studying the biology and hydrology of Cuatrocienegas, a rare and endangered desert oasis in northern Mexico. Covers research of Dean Hendrickson and Brad Wolaver.

The trout species of Mexico‘s Sierra Madre Occidental (SMO) range have been essentially ignored in science except for the efforts of Needham and Gard (1959) in the mid-20th century. Even after their work documenting the existence of the Mexican Golden Trout Oncorhynchus chrysogaster no focused efforts to study the diversity in the SMO south of the USA were initiated until 1997. Sampling in the Sierra Madre Occidental is extremely difficult, but our efforts since that year have revealed that all of Mexico‘s SMO trout are native (except for hatchery-reared) to the Río Yaqui system southward to the Río Acaponeta, and in the Río Conchos drainage. Morphological and genetic studies of the populations from these rivers support the hypothesis of multiple divergent lineages that we argue are distinct evolutionary species. Conservation and protection of these lineages are critical and should constitute a coordinated effort involving governmental agencies, private organizations, nonprofit groups, and individuals. More inventory work is warranted to better understand the distributions of the native trout and efforts should be made to eliminate the introduction of ―hatchery rainbow trout‖ Oncorhynchus mykiss into grow-out facilities in these mountains, instead replaced with propagation efforts on the different native species within their respective drainages. The diversity of wildlife and natural features across the SMO could, with proper planning and maintenance, serve as a fundamental, environmentally sound, sustainable resource for the region via ecotourism.

Collections of 231 catfish from 34 localities were surveyed for mtDNA (399 base pairs of cytochrome b) and morphological evidence of headwater catfish Ictalurus lupus in areas of historical occurrence in Texas and New Mexico. The species is of concern for conservation managers, primarily because of the potential for population losses from competition and hybridization with channel catfish I. punctatus. For cytochrome b, there were two deeply divergent (4.8–6.1%) groups, a channel catfish clade of 14 haplotypes (0.8% to 1.3% divergence) and a headwater catfish clade of two haplotypes (1.0% divergence), associated with morphotypes of channel catfish and headwater catfish, respectively. Morphotypes were based on field identification and a canonical discriminant function utilizing external morphology. All specimens from the Nueces River and the main-stem Rio Grande and the Pecos River conformed to morphological and mtDNA expectations for channel catfish. Apparently pure populations of headwater catfish were found only in two relatively isolated situations (Rocky Arroyo, New Mexico, and San Solomon Spring, Texas). Additional genetic evidence of headwater catfish was restricted to four populations in streams that are direct tributaries of either the Pecos River or the Rio Grande. Two of these populations (Independence Creek and Dolan Creek—Devils River) were morphologically distinct from, but shifted toward, the morphotype of channel catfish. A third population (Pinto Creek) was morphologically indistinguishable from channel catfish, and individuals from the fourth population (Delaware River) had morphotypes consistent with both species. The Pinto Creek, Independence Creek, and Delaware River populations exhibited mtDNA haplotypes from both species, whereas the Dolan Creek—Devils River population was fixed for a haplotype from the headwater catfish clade. A survey of early collection records tentatively suggests that hybridization between headwater catfish and channel catfish might be a result of relatively recent introduction of the latter to the Rio Grande basin.