Fish-based index of biological integrity (IBI) for Ecological Assessment in the San Carlos and San Antonio Rivers located in the APFF Canon de Santa Elena, Chihuahua, Mexico

Authors: De La Maza, Mauricio*, Lozano-Vilano, Ma. de Lourdes*, Contreras-Balderas, Armando J., Garcia-Ramirez, Ma. Elena

Year: 2015 (xlvii)

Abstract

The state of a river ecological health can be assessed through the analysis of its biological, physicochemical and habitat components, as well as the presence of invasive species. The Rio Grande (Rio Bravo) is crucial for the economic and social welfare of the extensive border region that exists between Mexico and the United States. Among the sites that have being identified as priority conservation areas by the Commission for Environmental Cooperation (CEC) are the San Antonio and San Carlos creeks, which are located within the limits of APFF CaÁƒÂ±ÁƒÂ³n de Santa Elena in Mexico. Originally, our hypothesis for this study considered that both systems were in fair ecological conditions. In order to determine the ecological status of both creeks, we designed an Index of Biological Integrity (IBI) for fish, and determined baselines for the metrics used, as well as other ecological parameters. Our results indicate 1) presence of moderate levels of fecal pollution probably coming from livestock and domestic waste; 2) creek sections with moderate to high eutrophication mainly from rural communities and agricultural runoff and irrigation returns; 3) presence of residual traces of heavy metals, which possibly originated from some of the abandoned mines in the region; 4) presence of 3 native species in both systems; and 5) invasion by the exotic species Fundulus zebrinus Fish and water samples were taken from 10 sites in both creeks; an extra control site was sampled from a nearby Arroyo El Chapo. In order to construct the IBI we considered the three native species identified, as well as 3 Á¢â‚¬Å“potentialÁ¢â‚¬Â and one exotic species for both sites. IBI scores for the various sites indicate different degrees of ecological impact. On a scale of 0 to 100, the Arroyo San Carlos scored 22, San Antonio 18, and their confluence 66; while nearby Arroyo El Chapo, located in the same hydrological sub-region scored 65. We recommend: 1) that livestock should be excluded from the riparian zones, 2) the treatment of waste water from small rural communities and 3) the construction of oxidation ponds to treat irrigation returns that cause eutrophication. Finally we recommend starting a restoration program, in order to restore habitat and species at specific sites, as well as a program for the control and/or eradication of exotic species.