Investigation launched after hundreds of fish found dead in Welsh stream

Nation.Cymru Staff

An investigation has been launched after hundreds of fish were found dead in a south Wales stream, with environmental officers appealing for information from the public.

Several members of the public highlighted the incident affecting both Roath Park Lake and sections of Roath Brook in Cardiff on Thursday 11 June.

The next day, local Senedd Member Shav Taj clarified that she had made enquiries with both Cardiff Council environmental officers and Natural Resources Wales following reports.

NRW then took to Facebook on Saturday 13 June to provide an update. They wrote: “We’re investigating a pollution incident at Roath Brook in Cardiff that has sadly led to the death of hundreds of fish of various species.

“Thankfully, live fish have also been observed in the brook at Waterloo Gardens since the incident.

“We thank members of the public for reporting their concerns to us on Thursday 11 June. An NRW officer attended the area and observed that the pollution appears to have stopped.

“It’s suspected the fish deaths may have been caused by something toxic being poured down a surface water drain, or a larger scale pollution, which we are investigating.

“The pollutant is believed to have passed through the brook. However, as a precautionary measure, dog owners may choose to keep their pets out of the water.

“Remember: only rainwater should go down surface water drains. Harmful chemicals, oils, paints, or cleaning products can cause serious damage to local wildlife and ecosystems if disposed of incorrectly.”

They requested that anyone who saw anything unusual, “such as someone pouring substances into a drain”, or with any other information contact them online or call 0300 065 3000.

The incident comes amid longstanding concerns about water quality in the Roath Park and Roath Brook area.

Research from Cardiff University and Natural Resources Wales identified Roath Brook as one of the most polluted urban watercourses examined in Wales.

In the study published earlier this year, elevated levels of pesticides commonly used in pet flea treatments were found in the brook’s water, although there is currently no evidence linking those findings to the latest incident.

Two pesticides from flea treatments, imidacloprid and fipronil, exceeded safe levels in almost half of the samples from urban locations across Wales.

Previously, Cardiff Council emails released following a Freedom of Information request in 2019 revealed discussions among officers about “unauthorised sewage discharges” into Roath Park Lake, which feeds the brook.

According to the Local Democracy Reporting Service, an unnamed individual wrote in an email: “We are aware that Roath Park Lake and other watercourses in the area do have some issues with unauthorised sewage discharge.”

Testing in previous years identified elevated levels of bacteria in the lake, with an individual in the council’s environment department writing that water samples gathered in 2012 and 2013 “indicated that bacterial levels within the water body were far in excess of recommended limits for immersion activities in fresh waters.”

At the time, Cardiff Council and Welsh Water said they believed the pollution was linked to a sewage misconnection from a commercial property.

Residents shared their concerns, with one writing that despite NRW confirming that there were live fish in the waterway, their numbers were low.

“This stretch of Roath Brook is usually teaming with fish,” one shared. “After yesterday’s pollution incident, I’ve only seen one that’s alive.”

Others highlighted that the issue has been ongoing “for years”, with dead fish and white scum reported previously, and suggestions that some household drains may be wrongly connected and emptying into local waterways.