| Summary: | Lake Tahoe Report Segment #151 - "Fish Species of the Lake Tahoe Basin" (Air Date: Jan. 9, 2006). Segment 151 - In terms of lakes, Tahoe is a relatively harsh environment for fish. It was cutoff from other bodies of water many thousands of years ago, so as it evolved, only seven species of fish evolved in it. However, since the introduction of humans and human intervention at Lake Tahoe, that number has changed. According to Brant Allen, fisheries biologist with the UC Davis Tahoe Environmental Research Center, “The original native game fish was the Lahontan cutthroat trout, which is no longer in the lake. But, there are still six native species of fish swimming in Tahoe.” The Lahontan cutthroat trout, named for the distinctive red streak under its chin, once topped Lake Tahoe’s food chain and weighed as much as 40 pounds. This fish thrived in the Tahoe Basin and migrated the length of the Truckee River between Tahoe and Pyramid Lake. The native fish that still survive in Lake Tahoe include: • The mountain whitefish (Prosopium willaimsoni) is Lake Tahoe’s only native game fish. It lives near the bottom to a depth of about 100 feet. • The Lahontan redside shiner (Richardsonius egregious) is a native minnow that is abundant in the shallow shorezone and can usually be seen in large numbers around marinas and rock crib piers. It grows to 3 to 4 inches long. • The Lahontan speckled dace (Rhinichthys osculus) is another native minnow that grows to about 2 to 3 inches long. It is difficult to find, as it seeks the cover of rocky substrate on the bottom of the lake. • The tui chub (Gila bicolor) is a bottom-oriented chub that feeds on zooplankton or sediments on the bottom of the lake. • The Tahoe sucker (Catostomus tahoensis) is a bottom feeder that grows to about 16 inches long. • The Paiute sculpin (Cottus beldingi) grows to about 3 inches long. It lives under rocks and is rarely observed in less than 10 feet of water. The native Lahontan cutthroat trout went extinct in Lake Tahoe in 1939, due in part to overfishing, competition with nonnative species, and the development of dams. In particular, Derby Dam below Reno and Sparks and the Tahoe Outlet Dam in Tahoe City isolated the Tahoe population of cutthroat trout from other populations within the historic range. Beginning in the late 1800s, when the effects of human environmental changes had reduced the numbers of Lahontan cutthroat in the lake, humans began introducing nonnative fish species in hopes of increasing Tahoe’s yield of game fish. These introductions included lake trout from the Great Lakes, Chinook salmon, Atlantic salmon, golden trout, Arctic grayling, Great Lakes whitefish, brook trout, brown trout, and rainbow trout. Of these fish species, the lake trout, brown trout, brook trout, and rainbow trout were able to establish self-supporting populations in the Tahoe Basin. In the 20th century, additional introductions of nonnative invertebrates and fish further altered the Tahoe Basin ecosystem. Using the best available science at the time, exotic species were introduced with the intention of adding a recreational component or supporting an existing fishery. Unfortunately, not all of the species behaved as expected in the clear, cold waters of the Tahoe Basin. After 70 years of alteration, the aquatic ecosystem now supports nonnative lake trout (Mackinaw) as the top predator. They are accompanied by rainbow trout, brown trout and kokanee salmon, providing multiple recreational fishing opportunities for shallow and deep-line anglers. The native Lahontan cutthroat trout is now among the most endangered western salmonids. Fortunately, as noted above, the other six native Tahoe fish species have survived the planned exotic introductions and continue to thrive within the Tahoe Basin. In recent years, new threats to Tahoe’s remaining native fish have arisen. A number of warm-water fish species have been illegally introduced to Lake Tahoe, including largemouth and smallmouth bass, crappie, and sunfish. While these fish are typically associated with warm-water environments, their populations are able to grow and spread within the Tahoe Basin. Taking advantage of seasonally warm water in bays and marinas, the fish feed on native minnows and successfully spawn. Scientists from University of California Davis and University of Nevada Reno plan to study the potential expansion of these species, and with help from the USDA Forest Service Lake Tahoe Basin Management Unit, implement a plan for their control. “The warm-water invasive species appear to pose a great risk to Tahoe’s remaining native species,” states Brant Allen a research biologist for UC Davis. “Their ability to consume large numbers of fish and the apparent overlap with native minnow spawning areas is a big concern.” Warm-water fish invasions are not new to California. Nearby Lake Davis continues to experience problems resulting from the illegal introduction of northern pike, a voracious predator. Controlling the spread of similar species in the Tahoe Basin could go a long way to preserving native fish and assist the recovery of Tahoe’s once great Lahontan cutthroat trout.
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