*Please note advance registration is now REQUIRED for Wild Tales.*
Spending time outside is one of the best ways to nurture curiosity and instill a love of the natural world. Bring your young ones and join OC Parks staff to learn about Upper Newport Bay.
Wild Tales is offered every Friday from 10-11 a.m. and includes a story time, age-appropriate hike and themed craft. Each week will focus on a different topic that encourages young ones to learn about the outdoors.
The program begins at the Peter and Mary Muth Interpretive Center. Program content is tailored for ages 2 to 5, but all are welcome to attend. Minors under 18 must be accompanied by a guardian. Please wear comfortable attire and closed-toe shoes.
The program and parking are free. Adverse weather may cancel the program or move it fully indoors.
Advance registration required. Learn more and register here. Registration opens two weeks prior to the program date.
For questions, please contact Resource Specialist Emma Arago at emma.arago@ocparks.com or call (657) 692-5401.
*Please note advance registration is now REQUIRED for Wild Tales.*
Spending time outside is one of the best ways to nurture curiosity and instill a love of the natural world. Bring your young ones and join OC Parks staff to learn about Upper Newport Bay.
Wild Tales is offered every Friday from 10-11 a.m. and includes a story time, age-appropriate hike and themed craft. Each week will focus on a different topic that encourages young ones to learn about the outdoors.
The program begins at the Peter and Mary Muth Interpretive Center. Program content is tailored for ages 2 to 5, but all are welcome to attend. Minors under 18 must be accompanied by a guardian. Please wear comfortable attire and closed-toe shoes.
The program and parking are free. Adverse weather may cancel the program or move it fully indoors.
Advance registration required. Learn more and register here. Registration opens two weeks prior to the program date.
For questions, please contact Resource Specialist Emma Arago at emma.arago@ocparks.com or call (657) 692-5401.
Friday, August 29, 2025: OC Parks has received the results of the necropsies performed on three bass fish that died during the incident. Bacteriology, histology, parasitology, heavy metals and viral hemorrhagic septicemia virus (VHSV) were tested. The testing yielded the following results:
Bacteriology: No significant issues detected.
Histology: Results were normal and showed no cause for concern.
Parasitology: No notable parasitic presence identified.
Heavy Metals: Some elevated levels were detected (notably cadmium and arsenic), but not at concentrations high enough to explain the mortality of approximately 500 fish. It is important to note that heavy metals (such as mercury, cadmium, copper, etc.) tend to persist in tissues over time.
Viral hemorrhagic septicemia virus (VHSV): Not detected.
Following this incident, OC Parks is taking steps to have the necessary equipment and resources in place to be more prepared and respond quicker should anything like this occur in the future. Inspection protocols are being thoroughly reviewed to identify where improvements can be implemented to minimize downtime and prevent future equipment failures. This includes increasing the frequency of inspections for critical components like manifolds and aerators and creating a preventative maintenance schedule. Additionally, remote lake monitoring options are being explored which will give better insights into changing lake conditions, allowing for a more proactive response.
Friday, August 8, 2025: OC Parks has completed a thorough analysis and review of multiple water samples collected throughout Laguna Niguel Lake and Sulphur Creek. No substances of significant level of concern were detected and healthy water qualities were observed. The results further add to the hypothesis that the fish die off incident most likely occurred naturally due to changing weather conditions throughout July.
Water sampling sites in Laguna Niguel Lake and Sulphur Creek. Click to view image.
During the summer months, phytoplankton (microscopic photosynthesizing algae) naturally occur in larger numbers. These organisms may bloom into sizable populations in warm weather when there is prolonged sunlight and little cloud cover. When this happens, phytoplankton will photosynthesize during the day, which can increase concentrations of dissolved oxygen in water, critical for fish survival. After sunset, phytoplankton and other plants in the lake ecosystem consume oxygen, causing dissolved oxygen concentrations in the water to fall.
When there is heavy cloud cover during the day, there may not be enough sunlight to sustain the phytoplankton bloom. This can lead to lower dissolved oxygen levels or a crash in the phytoplankton population. The drastic change can deplete dissolved oxygen and threaten fish and other organisms in the lake.
The graph belowshows July 2025 cloud cover data for Laguna Niguel. The data reveals little cloud cover in mid-July. The low cloud cover was immediately followed by high cloud cover for the next several days, ranging from 82% to 100% coverage. Experts believe this change likely reduced photosynthesis and dissolved oxygen production within the lake, causing this low oxygen event.While it is not believed to have had an effect on this incident, six aerators were also offline at the time, which could have impacted the conditions in the lake.
Laguna Niguel Lake cloud coverage July 12 – 22, 2025. Click to view image.
In these low oxygen conditions, fish in the lake likely would have sought areas with more oxygen, such as the incoming cooler water upstream in Sulphur Creek or near the Oxygen Saturation Technology Systems (OSTs) that were installed in the deep-water section of the lake in December 2024. Unfortunately, too many fish gathered in the creek at the location where the die off incident occurred. This could have been caused by a combination of factors including the shallow water depths in that area or insufficient dissolved oxygen for the number of fish that were in such a small area.
To ensure a thorough analysis of all possible factors that may have contributed to the die off incident, OC Parks worked closely with OC Public Works to collect water samples in three locations within Sulphur Creek, which is primarily fed by urban runoff. Samples were analyzed for nutrient content, water quality and several major classes of pesticides and metals. Healthy water quality levels were observed, and the findings concluded a toxic event likely did not cause the fish die off.
Dinetofuran and thiamethoxam, two neonicotinoid pesticides, were detected in Sulphur Creek at levels far below scientific benchmarks from the U.S. Enviornmental Protection Agency (USEPA 2023)1 and published studies (Finnegan et al. 2017)2.
An herbicide, glyphosate, was detected in one of three water samples collected from the creek at a very low concentration, just above the method detection limit. This particular water sample was collected outside the boundaries of Laguna Niguel Regional Park at a concentration far below the lowest toxic concentration. Click here to view the full pesticides report.
OC Parks is awaiting the results of the necropsy. Once received, further information will be shared.
1 USEPA. 2023. Dinetofuran DRAFT Biological Evaluation: Effects determinations for federally listed endangered and threatened species and designated critical habitats. Environmental Fate and Effects Division, Office of Pesticide Programs, USEPA, Washington, DC.
2 Finnegan, M.C., L.R. Baxter, J.D Maul, M.L. Hanson, and P.F. Hoekstra. 2017. Comprehensive characterization of the acute and chronic toxicity of the neonicotinoid insecticide thiamethoxam to a suite of aquatic primary producers, invertebrates, and fish. Environ. Toxicol. Chem. 2017 Oct;36(10): 2838-2848.
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, the map indicates the density and distribution of fish in 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.
Come learn all about wild cats, make a fun craft, and visit our Large Mammal Exhibit to watch our mountain lions and jaguar receive enrichment and treats!
Program is for ages 7-10 years old ONLY.
Cost is $5 per child (one parent included).
Phone registration is required. To register for a class, call 714-973-6846.
Come learn all about wild cats, make a fun craft, and visit our Large Mammal Exhibit to watch our mountain lions and jaguar receive enrichment and treats!
Program is for ages 5-6 years old ONLY.
Cost is $5 per child (one parent included).
Phone registration is required. To register for a class, call 714-973-6846.
Non-native and invasive plant species are invading our native habitat and open spaces. They aggressively compete with our native plants for resources and spreads rapidly once established. Monitoring, management, and removal of these plant species is an important aspect of land management and habitat restoration.
Help us to manage populations of invasive plants and remove them from the habitat. No previous experience is necessary, just a desire to work outside and get dirty! Snake chaps, gloves, and tools will be provided but please feel free to bring your own if you have them. Please wear long pants, long sleeved shirts, close toed shoes, and protective sun protection. Note: This is a wilderness area, there are natural hazards. Snakes, including rattlesnakes, are occasionally seen here.
Please note that you will be asked to adhere to the following measures in order to participate:
Be registered in advance, no walk-up registration is permitted.
Arrive with all necessary equipment to keep you safe on the trail, including water, proper attire, and closed-toe footwear, first aid, health needs etc.
Restrooms will be available, but facilities will not be sanitized for each individual.
All participants are required to sign a liability waiver upon arrival at the staging area and before beginning the activity. The waiver can be previewed here: IRC Liability Waiver
You may be prevented from participating if you do not adhere to the above protocols.
Additionally, in an effort to respect and protect all employees, volunteers, and participants, please do not sign up or attend if you are not feeling well, exhibiting any symptoms of illness or have been in recent contact with someone who was ill.
Reviewing the 1-through-5 Difficulty Ratings will help you evaluate your readiness to participate in this level-3 activity on the land.
