Community Partner

Lake Oswego Corporation

Date of Award

Summer 2009

Document Type


Degree Name

Master of Environmental Management (MEM)


Environmental Science and Management




Introduced aquatic organisms -- Oregon -- Lake Oswego -- Prevention, Introduced aquatic organisms -- Control -- Oregon -- Lake Oswego, Water quality management, Introduced organisms -- Oregon -- Lake Oswego, Lake Oswego (Or. : Lake)




This Invasive Species Management Plan defines an overarching strategy for the Lake Oswego Corporation (LOC) to mitigate threats from invasive species to Oswego Lake. Invasive species pose a direct risk to recreational and aesthetic uses of the lake, critical LOC infrastructure, and ecological communities within the lake. The Plan is particularly concerned with two bivalve mollusks in the genus Dreissena: the zebra mussel (Dreissena polymorpha) and the quagga mussel (Dreissena bugensis). These mussels grow in dense colonies that damage watercraft and underwater structures as well as displace native species. A recent scientific report found that an intense infestation of mussels in Oswego Lake is unlikely due to the water chemistry, but a low to moderate level of infestation is possible. Any level of infestation could be very serious and warrants proactive preventative measures and response plans should an invasion occur. In addition to the harmful mussels, this Plan identifies preventative and response measures for other species such as hydrilla (Hydrilla verticillata) that have the potential to harm Oswego Lake.

Strategies outlined in this Plan are as follows:

  • Identification and prioritization of likely potential invasive species
  • Identification of vectors of establishment
  • Prevention strategies
  • Development of monitoring plans
  • Rapid response action plans and control measures if an invasion is detected

Prevention is the top management priority for all invasive species as the cost and difficulty of controlling or eradicating an invasion increase significantly as an invasion spreads. This includes active measures to exclude species as well as the ongoing education and involvement of community members. Effective monitoring and rapid response action plans are the next priority to detect and eradicate an exotic species before it establishes and spreads. The integration of these strategies will help the LOC prevent significant deleterious effects from invasive species in Oswego Lake so that the basic operations of the LOC are facilitated and recreational and aesthetic opportunities are preserved.


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A project report submitted in partial fulfillment of the requirements for the degree of Master of Environmental Management.

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