Effects of a declining lake elevation and increasing TDS levels on Lahontan tui chub in Walker Lake, Nevada

Authors: Karie A. Wright

Year: 2012 (xliv)

Abstract

Over allocation of water rights in the Walker Basin, Nevada, has resulted in a decline in Walker Lake level. This decline has caused an increase in total dissolved solids (TDS) concentrations and resulted in a depauperate freshwater fish community. Walker lake TDS are mostly comprised of bicarbonate, sodium, sulfate, and chloride, which degrade gill and kidney functions and impact survivorship and size of fishes. Toxic TDS levels have eliminated other native fishes such as LCT (Oncorhynchus clarki henshawi), Tahoe sucker (Catostomus tahoensis), Lahontan redside shiner (Richardsonius egregious), and Lahontan speckled dace (Rhinichthys osculus) that once lived in Walker Lake. Lahontan tui chub (Siphateles bilcolor pectinifer and S. b. obese) are the last remaining fish species. Stage of egg development in tui chub was observed in order to document changes in viability as TDS concentration naturally increased in Walker Lake. Advanced development in tui chub embryos declined and an increase in deterioration was observed as TDS levels rose. An assessment of the tui chub population indicated a complete absence of cohorts under age three when TDS exceeded 15 g/L and once TDS exceeded 17 g/L, no cohorts under age five were found. Based on observed symptoms of physiological stress and mortality observed latter in the study the maximum tolerance of adults is likely to be around 20 g/L. At the conclusion of the study, gill net catch per unit effort (CPUE) was less than one tenth the CPUE from five years earlier when TDS levels were under 15 g/L. Understanding the effects of increasing TDS levels on tui chub provides resource managers valuable information that will aid in decision making for future management and restoration of the fishery as well as for future water acquisitions.