The receding waters of Walker Lake, Nevada: a history of its fishery and status update on the Lahontan cutthroat trout, Oncorhynchus clarki henshawi, and tui chub, Siphateles bicolor

Authors: R. Bruce Medhurst, David B. Herbst, Ian D. Bell

Year: 2012 (xliv)

Abstract

Walker Lake, Nevada, is a terminal lake which is one of two remaining relics of Pleistocene Lake Lahontan (the other being Pyramid Lake, NV). Walker Lake is fed by the Walker River which has experienced several large scale climate related fluctuations in discharge over its 40,000 year history but more recently, a significant and rapid reduction due to agricultural use over the past 130 years. Native Lahontan Cutthroat Trout, Oncorhynchus clarki henshawi, (LCT) populations began declining around 1860, and attempts to bolster the fishery through stocking began as early as 1909 when lake salinity was at 3.2g/l total dissolved solids. By the 1950s, with reduced river inflows and a lake salinity of 6.8g/l, natural spawning in the Walker River had diminished to an extent that the fishery was entirely dependent upon planted LCT from other populations. In an attempt to create a viable fishery, over 49 species of brackish and fresh water fish species were tested in Walker Lake, none of which survived salinities in excess of 8.4g/l in 1963 except LCT and native Tui Chub, Siphateles bicolor. The loss of aquatic invertebrates, a critical fish food resource, has also occurred with the amphipod Hyalella and seed shrimp Ostracoda disappearing in the mid 1980s at a salinity near 10g/l. By 1995, at a salinity of 13g/l, LCT required acclimation to saline water before planting in Walker Lake with limited success once lake salinity exceeded 15g/l in 2005. In an effort to restore Walker Lake, Congress enacted a law in 2005 that created a program to acquire water rights from willing sellers in the Walker Basin in order to send more water on to the lake. However, with current lake salinity in excess of 19g/l, the continued survival of Tui Chub, the remaining aquatic invertebrates on which they depend, and use of the lake by migrating water fowl is in question.