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Copper sulphate may be to blame for September Ferndale lake fish kill

Dead fish recovered from the shore of Agate Lake (September 19, 2020). Photo: Courtesy of a reader

FERNDALE, Wash. — Water samples along with dead waterfowl and fish specimens were reported taken from Agate Lake shortly after large numbers of dead fish were discovered floating along the lake shore beginning September 18th. Samples were sent to labs and the test results have recently been reported.

The Sandy Point Improvement Co. (SPIC) reported in a letter to property owners on October 27th that water quality samples taken and sent to a toxicology lab revealed the presence of copper sulphate.

According to Wikipedia, Copper sulphate is a commonly used in swimming pools to kill and prevent the growth of algae and copper ions are highly toxic to fish. It is readily available to purchase in retail stores under a variety of names and brands.

The Whatcom Humane Society performed necropsies on 2 waterfowl brought to them and sent tissue samples to a University of California laboratory in Davis, California. Executive Director Laura Clark said in an email on November 22nd the lab was only able to test for a few things due to the condition of the bodies and results were negative for organophosphates, a common form of insecticide.

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Agate Lake is 1 of many common areas around Sandy Point that SPIC manages and SPIC officials said they have hired a water quality company to manage it.

In the October letter to property owners, signed by Sandy Point Board of Directors Communications Officer Alicia Beck, SPIC said it does not treat with copper sulphate and warned property owners not to treat the lake on their own. The letter went on to say SPIC had contacted the Whatcom County Sheriff’s Office and “If a situation like this occurs again, SPIC will be pursuing all legal recourse available to it.”

SPIC also said in their letter “no further action will be taken and the lake is safe.”

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