Aquatic

Lake Tahoe’s original ecosystem was very simple, and consisted of only one predominant predator. Over time, some non-native species have been intentionally introduced to increase sport fishing or enhance ecosystem resources. Invasive species, non-natives that are harmful to the ecosystem, have also been introduced through unknown vectors. Click here for Lake Tahoe's food web and introducions from the past 100 years.

Aquatic Invasive Species harm Lake Tahoe by:
1.  Severely decreasing recreational uses, such as swimming, boating, water-skiing, and fishing
2.  Degrading boats by clogging propellers and cooling intakes
3.  Facilitating invasions of other non-native species
4.  Altering nutrient cycles and increasing algal growth in the lake by adding phosphorous to the water column thus contributing to overall clarity decline

Species of Concern

Presently in Lake Tahoe:
Eurasian watermilfoil
Curly leaf pondweed
Large mouth bass
Bluegill
Asian clam
Bull frogs

NOT Presently in Lake Tahoe:
Zebra mussel
Quagga mussel
New Zealand mudsnail

Native vs. Invasive Mollusk Identification Key

Native vs. Invasive Aquatic Plant Identification Key

Native and Invasive Fishes of the Lake Tahoe Basin

Current Projects

Asian Clam Pilot Removal Project

The Asian clam pilot removal project started in February 2009 with the objective of finding the most efficient method of controlling the existing clam populations. This project is a collabortive multi-agency effort utilizing various funding sources. A final report will be available early 2010.

Preliminary Project Findings:

1) Dissolved oxygen, under the bottom barriers, reached zero after an average of 36 hours

2) All of the clams in the samples migrated vertically within the sediment column under the barriers.

3) 100% clam mortality was reached after an average of 28 days

4) Impact to the native benthic community was significant

5) Bacteria counts are relatively high underneath the barriers, but decrease as you move away from them.

6) There is an abundance of Cladophora (filamentous algae) in Marla Bay, as

compared to the Zygnema sp. and Spirogyra sp. Compared to that observed last year. The bloom last year continued into October, there is still some time yet to determine the seasonal flux of this bloom.

Additional Findings:

1) Underwater Autonomous Vehicle (Gavia) surveys were conducted and produced preliminary results. This survey was a lakewide effort to determine the extent of Asian clam populations. The Gavia primarily surveyed the near shore (transects at 5m depth), but did detect a deep water population off Nevada Beach. This population was determined to be at a depth of 80m. Several ‘new’ populations of Asian clams were detected and include, Emerald Bay, Camp Rich and Glenbrook. Ground-truthing of the data needs to be conducted before a complete analysis can be completed.

Next steps:

1)      Pursue a ‘scale-up’ of the pilot project to management level, large scale operation

2)      Determine relationship between deep water populations and near shore populations

3)      Determine re-colonization of native invertebrates vs Asian clams

4)      Explore Asian clam removal opportunities in Emerald Bay

Aquatic Weed Removal Project