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Shrimp, Stonefly Populations Shrinking In Lake Tahoe



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(Sacramento, CA)
Wednesday, March 9, 2011

By Bob Moffitt

The Blind Amphipod Shrimp and Tahoe Stone Flies each have characteristics that make them unique to the lake. Fifty years ago, 3500 shrimp per square meter could be found on the bottom.  Today, six can be found in the same area.   

Annie Caires is with the University of Nevada Reno.  UNR just released the results of a two-year study of the shrimp, the flies and eight other species that are native to the lake.  She says the species are struggling to find food and shelter because the plants that provided both have all but disappeared.    

Annie Caires: "Those plants are adapted to pretty low light conditions, so they only need about one percent of the light to reach the bottom."

But she says that light is no longer reaching the bottom because of the decline in the lake's clarity from 1960 to 2000.

The species are also under attack from predators…crayfish, and a non-native species of Mysid Shrimp.  Mysid Shrimp were introduced in the 1960's by the California Department of Fish and Game and the Nevada Department of Wildlife.  to help feed the lake trout population.

Annie Caires: "They feed on these Benthic Invertebrates during the day and then they migrate up into the water column at night.  They do this because during the day, they are trying to avoid fish predation."

Caires says there have been successful efforts to trap the crayfish, but she doesn't think the Mysid shrimp can be eradicated.  The lake's clarity has been stabilized in the past ten years.  Caires hopes the clarity can be increased soon enough for light to once again reach the plants and special species that call the lake home… UNR hopes to have the funding for more studies of natural and man-made affects on the species…soon.

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