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.

This first meeting of those conducting scientific research in the valley of Cuatrociénegas, Coahuila, México and nearby regions was organized for the primary purpose of increasing and improving interactions among the diverse researchers working in the area, and to increase and improve communications between researchers, the management community (both government, NGO and private interests) and the general community of Cuatro Ciénegas.

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.

Convergence has long been of interest to evolutionary biologists. Cave organisms appear to be ideal candidates for studying convergence in morphological, physiological, and developmental traits. Here we report apparent convergence in two cave-catfishes that were described on morphological grounds as congeners: Prietella phreatophila and Prietella lundbergi. We collected mitochondrial DNA sequence data from 10 species of catfishes, representing five of the seven genera in Ictaluridae, as well as seven species from a broad range of siluriform outgroups. Analysis of the sequence data under parsimony supports a monophyletic Prietella. However, both maximum-likelihood and Bayesian analyses support polyphyly of the genus, with P. lundbergi sister to Ictalurus and P. phreatophila sister to Ameiurus. The topological difference between parsimony and the other methods appears to result from long-branch attraction between the Prietella species. Similarly, the sequence data do not support several other relationships within Ictaluridae supported by morphology. We develop a new Bayesian method for examining variation in molecular rates of evolution across a phylogeny.

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.

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 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.

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.