Hot weather thought to be cause of boating lake fish deaths

Hot weather is thought to be the cause of dozens of fish dying in a Wirral boating lake.

A large number of fish have been found dead in or around the boating lake off Gautby Road in the north end of Birkenhead. The water, which has a blue-ish appearance in photos, has led to unconfirmed speculation about the cause of the deaths.

It is believed hot weather last week led to a reduction in oxygen levels in the lake which caused the fish to suffocate as water temperatures rose.

The lake is understood to only be waist deep at its deepest point and it was not built as a fishing lake with little water flow.

A Wirral Council spokesperson said, “Gautby Road is a purpose-built model boating lake, it was never intended, nor should it be being used, for fishing or any other unauthorised activity.

“The indications are that fish have died due to a lack of oxygen in the lake caused by the hot weather experienced last week.

“As there is no plant life in the lake and it is a relatively shallow area of water, oxygen levels can drop quickly in hot temperatures and put any fish in that environment in danger.

“Occasionally the lake is treated with a DEFRA-approved commercial dye in order to control the levels of algae, however this is not toxic to fish, plants or other wildlife.

“That, plus the fact that no dye has been applied to the lake since May, means it is very unlikely for it to have contributed to the tragic death of these fish.”

Posts on social media had suggested the cause of death was the use of dye in the lake. Pond dyes are often used to limit algae growth and the lake previously had to be closed due to a bloom of toxic blue-green algae in 2021.

The use of dye is not considered harmful to fish and some brands suggest it can be beneficial to fish as it helps keep water temperatures lower.

According to the brand Dyofix, European regulations “have a fish test that uses the dyes in concentrations 1000 times greater than our suggested dose without any harmful effects”.

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Dead fish at Gautby Road. Credit: Wendy Connor