Friday, August 1, 2025: A Town Hall meeting to discuss the fish die off will take place Saturday, August 9 from 10 a.m. to 12 p.m. at Laguna Niguel Regional Park. Click here for more information and to register.
Wednesday, July 30, 2025: OC Parks has received the results of a hydroacoustic, sonar-based fish mapping survey throughout Laguna Niguel Lake. This high-tech method uses sound waves to assess fish population, distribution and habitat use in the lake. During the survey, sonar equipment emits sound waves into the water and records the echoes that return after bouncing off objects such as fish. The survey illustrates where fish are actively present within the lake and shows evidence of a healthy and sustained fish population.
As shown below, Laguna Niguel Lake. The numbers and contour lines represent the approximate water depth, and the brightest color yellow represents the presence of 10 or more fish within the zone.
Mapping shows the highest population density of fish are concentrated in the north end of the lake where the water is deeper and cooler. This is also where two oxygen saturation systems (OST) are located, which saturate the water with dissolved oxygen and are most effective when used in deep water. Please note, hydroacoustic mapping software does not show fish populations in water less than 3 feet deep, therefore fish in the shallower, south end of the lake may not be represented on this map. However, this mapping does provide a comprehensive look at fish abundance and distribution throughout Laguna Niguel Lake.
Hydroacoustic mapping completed Monday, July 28, 2025. Click map to access the document.
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.
Location of fish die off within Laguna Niguel Regional Park. Click map to access the document.
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.
