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.