18 June 2021

The Lake Mead Quagga Mussel Quandary: Reflections on My Remote Research with Invasive Mussels and Razorback Sucker

Written by: Elizabeth Renner

Ahoy! I’m Liz Renner and I’m a freshwater fisheries ecologist and Ph.D. candidate at Kansas State University in Manhattan, Kansas. My dissertation research in collaboration with the Kansas Dept. of Wildlife & Parks examines the ecological impact of zebra mussels (Dreissena polymorpha) and a nuisance baitfish called Gizzard Shad (Dorosoma cepedianum) in small impoundment food webs. This summer I’m working remotely as a DFP with the Southern Nevada Fish & Wildlife Office. For my DFP project, I am collaborating with a USFWS fish ecologist as well as aquatic ecologists with the Bureau of Reclamation to use 20 years of long-term water quality monitoring data to analyze the impact of invasive quagga mussels (Dreissena rostriformis bugensis) on an endangered native fish called the Razorback Sucker (Xyrauchen texanus) in Lake Mead.

Lake Mead is the largest reservoir by volume and the second-largest by surface area in the United States. First formed in 1935 following the construction of the Hoover Dam, the reservoir has been making the news in recent weeks for record-low water levels due to a prolonged megadrought across the Colorado River watershed. Lake Mead provides water to meet the municipal, industrial, and irrigation needs of 40 million people across seven states and Mexico. Unfortunately, Lake Mead is facing pressure from a growing list of ecological stressors, including anthropogenic climate change and aquatic invasive species. 

One such invasive species is the quagga mussel. Quagga mussels were first introduced to the Great Lakes from ship ballast water in the 1980s and were first detected in Lake Mead in the early 2000s. They have the potential to dramatically influence ecosystem productivity by selectively filtering out phytoplankton, leading to clearer, less productive water that is more concentrated with harmful cyanobacteria (blue-green algae).

So far my DFP project has involved a lot of data wrangling in Excel, but I find it pretty rewarding to compile and organize an entire database with 45,000 rows of data from scratch. My task for the summer is to analyze these data and prepare a report and presentation to the agency describing whether and how quagga mussels have impacted Lake Mead’s water quality. The productivity of the food web and water quality have direct impacts on endangered native fishes of the Colorado River like the Razorback Sucker, so our goal is to evaluate whether quagga mussels are making it more difficult for Razorbacks to survive and reproduce in Lake Mead, which is home to the last remaining population of pure, non-hatchery-stocked Razorback Sucker in the world.

I’ve dreamed of working as a fisheries biologist for the Service ever since I was 13 and watched electrofishing and fish stocking demonstrations by USFWS biologists when I attended a conservation camp for middle schoolers. That’s why I'm grateful for this opportunity made possible by the Hispanic Access Foundation for me to apply the knowledge I've gained from studying small Great Plains impoundments to the largest reservoir in the United States!  

Agency: U.S. Fish and Wildlife Service

Program: US Fish & Wildlife Service - DFP

Location: Southern Nevada Fish and Wildlife Office

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