New Mexico Geological Society Annual Spring Meeting — Abstracts

The semi-arid landscape of the southwest has been home to desert fishes for over 10,000 years.  Throughout this time, the fish have evolved in isolated niches during dry years and have mixed with high waters during wet years.  Today, due to land use practices and climate change, 20% of the native desert fish species are extinct.  Many more are listed as endangered (54) or proposed to be endangered (124), including the Zuni Bluehead Sucker (ZBS).  Once abundant in the Little Colorado River, the ZBS is now reduced to three spring-fed sections of 2nd and 1st order tributaries of the Zuni River in the Zuni Mountains, New Mexico.  My research focuses on one of the habitats for the ZBS, Agua Remora, an intermittent stream with headwaters located in the uplifted granite block.  A perennial hillslope spring flows into the channel some 2 km west of the continental divide.  At the spring site, several man-made pools are found.  Where the spring water flows into the channel and below, fish are present.  Above the spring input, ZBS are have not survived.  This research used spatial and temporal hydrogeochemical data to determine suitable habitat conditions for the species at the Agua Remora site.  These data will be used to better inform resource managers about the fish habitat and to ensure survival of the species.Beginning in May 2012, three sample sites were determined for the collection of water samples and continuous monitoring.  These sites included; 1. The spring (Spring) which is 15 meters away from the channel on a hillslope, and 2. A perennial pool in the channel above the spring input where ZBS are not found (Fishless) and 3.  A perennial pool in the channel below the spring where ZBS (Fish) have been found there since 2004.  Methods for the sites included seasonal field visits for ion and isotope analysis as well as continuous monitoring of physicochemical parameters including water temperature, specific conductance and dissolved oxygen.Analysis of major ions, indicate that the spring waters and the stream waters represent different hydrochemical facies, NaClSO₄ and CaMgHCO₃^- respectively, indicating they have different flow paths.  Isotopic analysis shows elevated δD and δ¹⁸O values indicating different recharge pathways for the channel water and the spring water.  Continuous monitoring of parameters suggests that the Fishless pool is anoxic after antecedent precipitation events with dissolved oxygen (DO) values < 2 mg/l for more than 30 days.  In comparison, the DO values in the Fish pool averaged 6 mg/l and rebounded after wetting events.  Spring waters have DO ranging between 1-4 mg/l.  These data suggest that the spring input is providing the necessary discharge conditions for re-aeration during low flow.  The spring water also lowers the residence time in the Fish pool making the habitat more suitable for ZBS after infrequent precipitation events.