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North Cowichan taking on Somenos Creek invader

Strategy outlined to deal with invasice species

Efforts to bring the outbreak of parrot’s feather in Somenos Creek under control, using a variety of strategies, are expected to begin soon.

North Cowichan earmarked $25,000 of initial funding towards mitigating the invasive aquatic weed in the creek at the council meeting on July 17.

The decision was made after a report on the issue and a suggested management plan was presented by Dr. Dave Preikshot, an aquatic biologist with the Somenos Marsh Wildlife Society and Madrone Environmental Services, who was contracted by the municipality to study the issue and develop recommendations.

The money will be given to the Somenos Marsh Wildlife Society to purchase water monitoring and other required equipment recommended in the management plan.

Preikshot said that within two years of introduction of parrot’s feather in Somenos Creek in 2014, it had reached such abundance and density that it now poses a threat to salmon migration, trout habitat, recreational uses by residents and their assessed property values.


He said management options to control parrot’s feather in the creek include dredging, the use of herbicides and shading.

“Experience in other jurisdictions suggest that, in the absence of drying infested habitat for three or more years, none of the available management options is likely to yield total eradication of parrot’s feather in Somenos Creek,” Preikshot said.

“While the use of herbicides would quickly reduce the abundance of parrot’s feather, re-infestation is almost certain and the use of chemicals in the aquatic environment would come at a high administrative and social cost. Previous scientific and engineering advice suggests that trees and shading would be effective in reducing aquatic plant biomass over a time span of years to decades.”


Approximately $15,000 of the funding from the municipality is intended to purchase shading material and planting equipment.

Parrot’s feather is a popular aquatic garden species and intentional planting has spread it into natural water bodies.

The species is known to out-compete and replace native aquatic vegetation with its dense stands, and has impacted a number of freshwater bodies in B.C.

Once established, parrot’s feather is a difficult invasive plant to manage.

Several homeowners adjacent to Somenos Lake sent a letter to the municipality last year outlining the problem.

The homeowners said they believe that the lake is effectively being blocked at its outlet by dense mats of parrot’s feather that have been allowed to grow unimpeded since first identified in Somenos Creek.

They said that, besides interfering with water flow and the salmon and trout in the waterways, parrot’s feather is creating stagnant water, which creates hazards such as a breeding ground for mosquitoes near a large urban area.

Preikshot said the monitoring of Somenos Creek should begin as soon as possible to establish baseline conditions of water quality, the abundance and distribution of parrot’s feather and stream depths.

“A combination of shading approaches and strategic dredging would be the most cost-effective approach to controlling the growth of parrot’s feather so that it doesn’t interfere with biological, social and economic values of Somenos Creek,” he said.

“Federal and provincial agencies and ministries are not likely to act unilaterally on parrot’s feather control work. However, the successful establishment of a management program and the commencement of monitoring and control work will likely attract financial support from senior levels of government. Reporting on the progress of the management program should be done annually.

Council also directed staff to send the parrot’s feather management plan to the province’s invasive plant officer for review, comment and consideration for future financial assistance.

Robert Barron

About the Author: Robert Barron

Since 2016, I've had had the pleasure of working with our dedicated staff and community in the Cowichan Valley.
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