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Pacific Southwest Research Station


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Natural and human limitations to Asian clam distribution and recolonization—factors that impact the management and control in Lake Tahoe

Proposal [pdf]

Lead Researchers:

Marion Wittmann, John Reuter and Geoff Schladow, Tahoe Environmental Research Center, UC Davis; Sudeep Chandra, Department of Natural Resources and Environmental Science, University of Nevada Reno


The invasive bivalve, Asian clam (Corbicula fluminea) is established and spreading in Lake Tahoe. In 2002, low density populations (2-20 individuals per m2) were observed in the south eastern portion of the lake, and in 2009 densities up to 5000 individuals per m2 have been measured. Through extensive field collection and laboratory experimentation, the UC Davis (UCD) – UN Reno (UNR) science team has found that this expanding population has already had significant ecological impacts on native benthic invertebrate biodiversity, has promoted filamentous algal blooms and is changing water chemistry as well as aesthetic value of the Lake Tahoe nearshore through shell deposition. In rapid response to this nearshore invasion, federal and state agencies collaborated with UCD and UNR to develop a short term Asian clam management plan and implement a series of studies to understand the distribution, life history and reproductive strategies of this species in relation to population control. Additionally, a series of non-chemical management strategies have been tested in small scale pilot projects in Lake Tahoe. Findings from this research have shown that Asian clam is distributed mostly in south eastern portion of the lake, with some low density satellite populations in Glenbrook Bay, Camp Richardson and Emerald Bay. Asian clam are located at depths greater than 70 m, which is deeper than the scientific literature has described or studied. The contribution of these deepwater clam populations to nearshore populations, as well as the growth, life history or reproductive strategies of this species in a temperature limited environment is unknown. Asian clam is an environmentally tolerant species, and there are few management strategies available. The UCD-UNR research team has found that by laying rubber bottom barriers over clam beds, it is possible to reduce dissolved oxygen concentrations to 0 mg/L and that after an approximate 1-2 month period, there is 100% mortality of clams under this barrier. There is potential for population reduction of this species in Lake Tahoe using this method, but it is important to consider the feasibility of implementation given economic costs, and more importantly, the recolonization rate of Asian clam--given propagule pressure from advective transport of juveniles via water currents, and diffusive spread of adjacent populations (including the recently observed deep water beds). Recent empirical studies have demonstrated the potential for increased mortality (such as that caused by invasive species removal harvest) to lead to overcompensation (increased population growth) in invasive populations, including well known aquatic invasive species such as Asian clam, zebra mussel and river snails (Zipkin et al. 2009). The understanding of the interaction between the ecology and management of an invasive species is key toward a successful control program. The major objectives of this proposal are to (1) understand the life history (including reproduction and growth) of deepwater clam populations and their relationship with associated benthic macroinvertebrate communities, chlorophyll concentrations, temperature, water currents and nearshore clam populations as a potential source or sink of recruits, (2) develop the relationship between treatment site selection (i.e., low population density site versus high density population center site) and rate of Asian clam recolonization, and (3) perform a cost efficiency analysis of rubber bottom barrier application that is dependent on recolonization rate and site selection.

Relation to Other SNPLMA Projects

This project builds upon the Round 9 SNPLMA science project, "Development of a risk model to determine the expansion and potential environmental impacts of Asian clams in Lake Tahoe".

Expected date of final products:

May 2012

Last Modified: Mar 28, 2013 02:52:07 PM