Fish trackers study movement of Tahoe bass
August 29, 2009
Legend has it that a prehistoric beast similar to the fabled Loch Ness Monster roams the depths of Lake Tahoe.
While the “Tahoe Tessie” myth holds more whimsy than weight, researchers from the University of Nevada, Reno, were at Lake Tahoe this week tagging beasts that could have real consequences for the lake’s historic underwater inhabitants.
Joined by employees of the California Department of Fish and Game, the researchers used two boats equipped with electrofishing equipment to catch 24 largemouth bass in the Tahoe Keys on Wednesday afternoon as part of a new study of warm-water fish in Lake Tahoe.
The largemouth bass is one of several warm-water fish species that were likely introduced – either intentionally or accidentally – into the lake by anglers in the mid-1980s and appears to be spreading around the lake’s near shore areas, according to recent research.
The fish may be contributing to a decrease in the number of native fish species in the lake since 1960, said Sudeep Chandra, a University of Nevada, Reno professor who studies invasive species at the lake.
Bass are voracious predators that eat native fish – like minnows and trout – or out-compete those species for food and habitat, added Stafford Lehr, senior fisheries biologist supervisor with the California Department of Fish and Game.
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“They are having an impact on the native fishes of Lake Tahoe,” Lehr said.
Some of the bass caught Wednesday weighed more than 6 pounds.
In addition to the University of Nevada, Reno, and the Department of Fish and Game, the study that began Wednesday is sponsored by the U.S. Forest Service and the Tahoe Resource Conservation District. The study is a follow- up to a pilot project last year that showed warm-water fish species were able to leave the relatively warm refuge of the Tahoe Keys for other parts of the lake as early as July, sooner than researchers anticipated, Chandra said.
In the latest study, bass were stunned using electroshocking equipment and brought on shore, where researchers sedated them using club soda. Researchers then made a small incision on the bass’s bellies to implant two tags, before stitching the fish back up and returning them alive near the area they were caught.
One tag – a computer chip similar to what are often implanted into cats and dogs – will stay useful to researchers throughout the life of the fish and may allow them to one day estimate the total number of largemouth bass in the lake, something that remains unknown to scientists, Chandra said.
The second tag is an acoustic tag that will operate for more than a year and will allow researchers to track movements of the bass through the Keys.
By studying bass movements past 13 receivers that have been placed in the Keys during the next two years to pick up signals from the acoustic tags, researchers should be able to determine how often bass leave the Keys and gain greater knowledge about what triggers them to do so, Chandra said.
Researchers also hope to gain a greater understanding of how warm-water fish interact with the invasive plants – like Eurasian watermilfoil and curly-leaf pondweed – that are spreading around the lake and are already ubiquitous in the Keys, Chandra said.
The information gathered during the latest study will likely be critical to understanding how to protect the dwindling number of native fish species in the lake, Chandra said.
Both Lehr and Chandra expressed doubts about whether warm-water fish species could ever be eliminated from Lake Tahoe, but said this study will be critical step to figuring out what to do next.
“You first have to have a good understanding of the problem,” Lehr said.
Because the species were introduced to the lake relatively recently, the spread of the species can likely be controlled, Chandra said.
Using electrofishing to remove fish from the lake and eliminating the dense underwater forests of milfoil and pondweed where the warm-water fish thrive are two ways the populations of the fish species in the lake could potentially be limited, Chandra said.