ABSTRACT. Meeting opening dedication

ABSTRACT. Cuatro Ciénegas has a rich history and is a place that has sustained life for millions of years. Throughout human history, people have inhabited it and exploited its resources. The modern history of Cuatro Ciénegas begins with a milestone: its founding as a town, but is preceded by attempts at settlement and hacienda by the Spanish and/or New Spaniards. However, evidence of material culture dates back 5,000 years, continuously inhabited by a single people, the Ndé, who have several tribes or gonka. Those who inhabited Cuatro Ciénegas are known as the Tobosos and later by the Natage, known as Mescalero Apaches. The resources found in the Cuatro Ciénegas Valley, such as animals, plants, and stones, used by the Ndé, both for consumption and processing, will be discussed.

ABSTRACT. Over the last decade, evidence has accumulated that water level declines in Cuatrociénegas, the world’s most biodiverse spring-based wetland and an important Mexican desert biodiversity hotspot and protected area, are related to largescale groundwater-based agriculture in adjoining valleys that contribute to the aquifer that feeds its springs and wetlands. At the same time, the area has transformed into a popular tourism destination, with rapid and massive expansion of the hotel industry and visitation. However, two of the primary developers established non-profit foundations with conservation- and community-support objectives, and are working together with the Federal Reserve System (CONANP), local conservation groups, regional universities, and the municipal government to assure that development is sustainable and compatible with biodiversity conservation. Much remains unknown about basic ecology and genetics of its highly endemic and diverse fish fauna, its three endemic turtles (not to mention many other endemic herps, invertebrates and plants) and there are new initiatives working to support field and laboratory research, as well as establishment of captive breeding programs. Hydrogeology/karst aquifer expertise is obviously also important. This talk will review the history of biological and hydrological explorations in the valley, as well as the role of Desert Fishes Council in the valley over the last 50+ years, and provide an update on the current conservation status of the valley. The Desert Fishes Council (https://www.desertfishes.org/) meeting in Cuatrociénegas in November of this year will provide opportunities for others to learn more and possibly become involved.

ABSTRACT. An overview of Mexico's Protected Areas system with emphasis on the responsibilites and projects of the Cuatrociénegas Protected Area Office with focus on endangered and invasive species and the diverse challenges of assuring sustainable of the fauna and flora of this important ecosystem.

ABSTRACT. This presentation provides an overview of the ecological significance of Cuatro Cienegas, focusing on its unique hydrological features that support a highly endemic and diverse biota. It discusses current conservation methodologies implemented by Fundación Pro Cuatro Cienegas, including habitat restoration, water management strategies, and species recovery programs targeting geographically isolated and threatened species. The session emphasizes the integration of scientific research, community engagement, and sustainable practices to promote landscape resilience and ecological integrity in this desert ecosystem.

ABSTRACT. The Coahuila Center for Biodiversity Conservation and Ecology Research at the Autonomous University of Coahuila (CICBEC of the UAdeC) seeks to contribute to the conservation of biological diversity in regions that, due to their characteristics, are unique in the world, with an emphasis on the state's desert zone. This is achieved through cutting-edge, high-quality scientific research, collaboration with rural communities, and the dissemination and application of the knowledge generated. CICBEC conducts specialized research in biotechnology, specifically focusing on the sustainable use of plant and microbiological resources in the Cuatro Ciénegas Valley for agricultural applications. The center also employs researchers certified by the National Forestry Commission (CONAFOR) to carry out technology transfer projects focused on candelilla wax and the use of the creosote bush. CICBEC hosts students from various regional and national institutions, showcasing the research generated in Cuatro Ciénegas at the federal and international levels.

ABSTRACT. The increase in groundwater extraction from the El Hundido aquifer, Coahuila, in early 2001 raised significant concerns about the potential adverse effects on the adjacent Cuatrociénegas aquifer, which contains a great diversity of endemic species. In 2004, IMTA [1] conducted a study to evaluate the hydrodynamic, isotopic, and geochemical behavior of the El Hundido aquifer and its possible interaction with the Cuatrociénegas aquifer, Coahuila. The main results of the study indicate that there is a hydrodynamic divide between the Cuatrociénegas and El Hundido aquifers and that the groundwater in Cuatrociénegas is isotopically different from that of El Hundido. It was recommended to instrument the Cuatrociénegas valley basin to more accurately determine the variables involved in calculating the hydrological balance and groundwater availability. In 2007, IMTA [2] constructed 11 monitoring wells in the western portion of the aquifer, while in 2014 [3] the instrumentation of the eastern portion was completed with the construction of 5 additional monitoring wells (Figure 1). The wells were equipped with automatic measuring instruments (leveloggers-barologger), which have now reached the end of their useful life, so the replacement of these instruments is underway to continue monitoring groundwater levels. To date, records of static water levels are available from 2008 to 2018. This paper presents the main results of the studies carried out by IMTA, as well as the progress made in reactivating the monitoring network for the static water levels of the Cuatrociénegas aquifer in Coahuila. [1] Aldama, Á.A., Aparicio, J., Gutiérrez-Ojeda, C., Martínez-Morales, M., González-Hita, L., Herrera-Zamarrón, G., Mata-Arellano, I., Mejía-González, M.A., Ortiz-Flores, G., Gallardo Almanza, P., Lobato-Sánchez, R., Pérez-López, J.L., Reza-Arzate, G., Fritz, P., Ramírez-Espinoza, J. & Cardona. A., (2007). Comportamiento hidrogeológico de los acuíferos Cuatrociénegas y El Hundido, Coahuila, México. Ingeniería Hidráulica en México, Vol. XXII, no. 3, July-September, 2007, pp. 37-59. [2] IMTA, 2007, Estimación del balance y la disponibilidad del acuífero Cuatrociénegas, Coahuila-1a. Etapa. Proyecto TH0727.1 de Recursos Fiscales. [3] IMTA; 2014, Red de monitoreo automática de niveles piezométricos del acuífero de Cuatrociénegas, Coahuila, Proyecto TH1405.1 de Recursos Fiscales.

ABSTRACT. High permeability karstic aquifers and low recharge rates in arid and semi-arid regions lead to the formation of extensive (often interbasin) regional flow systems such as are documented in Cuatrociénegas valley. The flow system discharges to springs that support unique spring-fed ecosystems. The springs occur in lines parallel to the Sierra San Marcos that divides the valley into west and east sub-basins, The west sub-basin hosts fracture-controlled springs with relatively high and constant discharge, elevated temperatures, and high conductivity. The east sub-basin is comprised of dozens of stratigraphically-controlled small springs adjacent to alluvial fans with lower temperature, lower conductivity, and relatively low discharge affected by precipitation. Isotopic data (tritium, 2H/18O, and 3H/3Hetrit) from the springs show that regional groundwater flow predominates with local recharge also occurring in the mountains surrounding Cuatrociénegas and also that mountain recharge older than 50 years predominates. Analysis of permeability and recharge data predicts recent interbasin flow from the Ocampo Valley to the north and the Hundido Valley to the southwest and perhaps farther. Limited by sparse data, research on quantification of the flow system in this karstic regional aquifer system and the precise locations and rates of local recharge is required to preserve spring flows, which are also threatened by climate change, population growth, and aquifer overpumping. This will require more water wells, pump tests, and water quality data on local and regional scales.

ABSTRACT. The arid and semi-arid regions of our planet support extraordinary freshwater biodiversity but its long-term sustenance requires maintaining a delicate balance between water consumption and natural replenishment. Preparing a detailed and accurate water budget that accounts for both replenishment (inputs) and all forms of consumption -- both human and environmental -- is a crucially important foundation for successful water governance. A water budget helps water managers and users to understand how and where water is being consumed, and whether a condition of overdraft or unsustainable use exists. Groundwater systems are particularly difficult to manage well, due to limited natural recharge (replenishment) and the pervasive use of aquifers as primary water supplies in dry regions. When aquifers are being overdrafted, a variety of corrective strategies must be implemented to bring the hydrologic system back into a sustainable balance. The Cuatro Cienegas aquifer system has been in an overdraft status since 2012, due to a combination of reduced replenishment driven in part by climate warming, and an expansion of water consumption for both domestic use and in irrigated agriculture to produce alfalfa, fodder corn, and fodder oats. This presentation will summarize available management solutions based on examples from dry regions around the globe.

ABSTRACT. Cuatro Ciénegas, Coahuila, Mexico, is one of the most unique freshwater ecosystems in North America, comprising more than 200 variably interconnected aquatic bodies that sustain exceptionally high levels of endemism (Fensham et al., 2023). According to Hendrickson et al. (2008), the basin supports sixteen native fish species, eight of which are endemic. Cuatro Ciénegas Shiner, Cyprinella xanthicara, Longfin Gambusia, Gambusia longispinis, Cuatro Ciénegas Platyfish, Xiphophorus gordoni, Cuatro Ciénegas Pupfish, Cyprinodon atrorus, Bifasciate Pupfish, Cyprinodon bifasciatus, Interior Killifish, Lucania interioris, Minckley’s Cichlid, Herichthys minckleyi, and Cuatro Ciénegas Darter, Etheostoma lugoi.

These endemic and other native species face critical threats from invasive alien species (IAS) such as Blue Tilapia, Oreochromis aureus, Jewel Cichlid, Hemichromis guttatus, Common carp, Cyprinus carpio, Louisiana Crayfish, Procambarus clarkii, and the Asian Snail, Melanoides tuberculata. Although not included in this study, invasive plants such as Giant Reed, Arundo donax, and Saltcedar, Tamarix ramosissima, are also present and are known to cause extensive ecological impacts in other regional drainages. These invasives have disrupted ecological balance by altering native fish assemblages, increasing interspecific competition, and degrading aquatic habitats, reportedly leading to sharp declines in native fish populations.

While the Comisión Nacional de Áreas Naturales Protegidas has implemented invasive species control programs in Cuatro Ciénegas, their long-term effectiveness has not been formally evaluated. This study aims to address that knowledge gap by (1) assessing current fish assemblages, (2) quantifying the abundance and distribution of native and invasive species, and (3) evaluating the effectiveness of previous control strategies. Through a combination of field surveys, stomach content analyses, and literature review, we aim to generate an integrated dataset describing the status of native and invasive fishes to inform future science-based management and guide the effective removal of high-impact IAS for the long-term conservation of native freshwater biodiversity in the Cuatro Ciénegas Basin.

In addition, the study will compare multiple resource-use areas characterized by varying levels of extraction restrictions to assess their potential effects on fish assemblages and associated habitat conditions. Sampling will also encompass sites with high levels of tourism activity as well as remote areas, allowing for a comparative analysis of anthropogenic pressure and ecological integrity. Together, these efforts seek to provide evidence-based insights to strengthen management actions supporting the long-term persistence and resilience of this globally significant ecosystem.

ABSTRACT. Carbonate geology and karst aquifers are widespread, representing 15% of the global, ice-free, continental surface. Calcium carbonate precipitation in karst ecosystems reduces water clarity and light availability, streambed stability, and phosphorus (P) availability, all of which have the potential to limit primary and secondary production. We investigated these potential abiotic effects on ecosystem production and food web dynamics using a spatial gradient of calcium carbonate precipitation in the Little Colorado River, AZ, USA, which is one of the population strongholds of the threatened Humpback Chub (Gila cypha). We found that both light and phosphorus availability were higher in the upstream, low-precipitation reach of the river during karst spring-fed baseflow conditions, but this spatial gradient weakened when overland flows produced by rainfall events added to base flows. Nutrient assays demonstrated that primary production was limited by phosphorus availability throughout the river suggesting that the increased P availability we documented in upstream low-precipitation reaches is likely supporting higher rates of autochthonous production in these locations. Emergent aquatic insects, an important prey resource for Humpback Chub and other fishes, were also more abundant at upstream, low-precipitation sites. Previous work has demonstrated higher juvenile Humpback Chub growth rates in the upstream, low-precipitation sites, suggesting that calcium carbonate precipitation is regulating food web production and fish growth. As calcium carbonate precipitation is a common feature of karst-fed aquatic ecosystems worldwide, our work suggests that processes that regulate calcium carbonate precipitation rates are an underappreciated control on light and phosphorus availability with implications for freshwater food web and ecosystem processes.

ABSTRACT. The North and Northeastern regions of Mexico include the states of Sonora, Durango, Chihuahua, Coahuila, Nuevo León, and Tamaulipas. This area encompasses six biogeographic provinces, highlighting its ecological, economic, and energy-related significance, with a complex territorial and environmental dynamic. Its main economic activities are mining, manufacturing, commerce, and various urban services. The region features a diversity of water systems, including rivers, aquifers, lagoons, and wetlands, although many of these face pressures from overexploitation and climate change. It relies heavily on underground aquifers, especially in arid zones such as Chihuahua, Coahuila, and northern Nuevo León. These extreme environmental conditions—particularly the lower number of freshwater bodies compared to central and southern Mexico—result in a biodiversity that is generally distinct from the rest of the country, especially regarding freshwater ecosystems. The Ichthyological Collection of the Universidad Autónoma de Nuevo León has recorded 209 species in Northern Mexico between 1966 and 2019. These species are distributed across 90 genera, 38 families, and 21 orders. Among the northern states, Tamaulipas is represented by 59 species, making it the state with the highest species richness; however, it is important to note that many of these species were recorded in Laguna Madre, Tamaulipas, so their affinity is not exclusively freshwater. The second most species-rich state is Chihuahua, with 56 species, followed by Coahuila with 39. Sonora is represented by only three species, mainly because most of the species recorded in that state are marine. The most represented orders in the northern states are Cypriniformes (29.6%) and Cyprinodontiformes (26.7%). The most represented families are Leuciscidae (21.8%), Poeciliidae (14.6%) and Cyprinodontidae (8.7%). Since 2020, the region has experienced significant hydrological changes, which may affect the ichthyological biodiversity of its water bodies. This underscores the need for ongoing monitoring and the development of ecological studies that provide specific and updated information to support more effective management strategies under various future scenarios.

ABSTRACT. The Sonoyta pupfish (Cyprinodon eremus) and the longfin dace (Agosia chrysogaster), native species of the Sonoyta River, a binational basin between northwestern Mexico and the southwestern United States of America (USA), are in danger of extinction (PROY-NOM-059-SEMARNAT-2025 and IUCN Red List). For more than 25 years, a binational working group (BWG) has brought together experts from various institutions who developed an ex situ conservation strategy or refuges, where populations of both species are protected, with some refuges emulating the Sonoyta River habitats. The refuges aim to promote habitat diversity, which contributes to genetic variability, safeguarding the species due to their extirpation (local extinction) in their natural habitat. The BWG has dedicated technical, financial, and management resources to maintain and raise awareness about the loss of these freshwater species in the Sonoran Desert. Simultaneously, community outreach actions have been carried out to sensitize local inhabitants about the importance of these species, strengthening social participation in conservation. This effort represents the firm conviction of experts and institutions from the USA and Mexico to prevent the extinction of two native freshwater fish species and sets the course for resources to be secured in the coming years to sustain the project, including increasing the number of refuges and implementing the design of re-population programs in the natural habitat. This project is supported by: the NPS, the OPWR, the CPWR, the ASDM, the CONANP, the DICTUS, and the CEDO.