Date of Award:

5-2024

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Watershed Sciences

Committee Chair(s)

Phaedra Budy

Committee

Phaedra Budy

Committee

Robert Al-Chokhachy

Committee

Janice Brahney

Abstract

Lake level decline affects lakes worldwide, changing the availability and character of nearshore habitat used by fish to spawn, and increasing total dissolved solids (TDS), similar to salinity, a factor that negatively impacts fish health. Lake level decline can affect different lakes in different ways, but typically when lake level declines significantly, there is less nearshore habitat overall, and what nearshore habitat remains has less diverse habitat for fish. We investigated whether both impacts of lake level decline may be causing declines of Tui Chub Siphateles bicolor, a large minnow native to Pyramid Lake that spawns in nearshore habitat. Tui Chub are the main food source for Lahontan Cutthroat Trout, a sought after, and vulnerable, sportfish also native to the lake. Pyramid Lake declined 98 feet from 1891 to 1967 because of human water use and remains low today. We used nets to capture Tui Chub during their spawning season to determine their preferred spawning habitat. We then used topographic data of the Pyramid Lake basin to understand the amount of spawning habitat at historical, and potentially future, lake levels if lake levels continue to decline in Pyramid Lake. We tested the response of Tui Chub eggs and larvae to TDS by spawning Tui Chub at a range of TDS levels. Based on our results, Tui Chub spawn in some of the warmest water found in Pyramid Lake during the summer and seek rocky areas to deposit their eggs, habitat features that may be reduced in Pyramid Lake with further lake level decline. With an additional 26 feet of lake level decline, Pyramid Lake will have less nearshore habitat than all other historical and contemporary lake elevations we investigated, potentially seriously restricting habitat available for Tui Chub spawning. Tui Chub eggs and larvae in our experiment were unable to hatch at TDS levels greater than those already found in Pyramid Lake. However, we experienced artificially high levels of toxic ammonia in most replicates such that all egg deaths could not be attributed to the TDS treatments. Our results have important implications for water demand for Pyramid Lake to make sure there are enough Tui Chub to support the population of Lahontan Cutthroat Trout in the lake.

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Creative Commons Attribution 4.0 License
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