Friday, July 25, 2025: As of Thursday, July 24, all cleanup efforts from the recent fish die off within Sulphur Creek near the south end of Laguna Niguel Lake have concluded. Approximately 500 fish were affected, predominantly bass and bluegill, and there have been no reports of additional fish surfacing.
OC Parks continues to work closely with experts in the field to monitor the current conditions of the lake. Water samples from multiple locations and depths have been collected to test water quality, including temperature, dissolved oxygen (DO), pH, and conductivity (salinity). Hydroacoustic fish mapping is also being conducted to assess the remaining fish population in Laguna Niguel Lake.
Wednesday, July 23, 2025: OC Parks is saddened by the recent fish die off that occurred at Laguna Niguel Lake within Laguna Niguel Regional Park and have been working around the clock to address the situation. We understand the importance these lakes have for the community and want to stress that we are taking this very seriously.
While we cannot definitively say exactly what caused this to happen, as fish die offs can occur naturally from time to time, a combination of factors could have contributed to the situation such as changing weather, increase in water temperature, a lower than average rainfall year, the presence of algae and potential equipment malfunction.
As of now, it appears the fish die off was due to a change in weather causing the water temperature to increase, particularly in the shallow waters at the south end of the lake where most of the fish were seen on the surface. When this happens, there is less oxygen in the water, which is critical to fish survival. Catfish can tolerate the warmer, desert-like conditions present in Laguna Niguel Lake this time of year, but other fish are more affected, seemingly leading to this fish die off. While there is no way to control the water temperature of the lake, further steps are being taken that could possibly help mitigate this from occurring in the future.
OC Parks cares deeply about providing the necessary conditions for fish to survive and thrive in the lakes under our management. All equipment has been thoroughly checked to certify everything is functioning properly. Additionally, we are continuing to monitor water temperature and oxygen levels within the lake to ensure conditions remain stable.
As of Wednesday, July 23, most of the cleanup efforts have concluded, with only a handful of fish surfacing over the last 24 hours. When visiting Laguna Niguel Regional Park, should you ever encounter any wildlife in distress, please contact the park office at (949) 923-2240.
