A massive fish die-off at Laguna Niguel Regional Park has prompted officials to investigate the cause.
Orange County Fifth District Supervisor Katrina Foley said the die-off was mainly bass and was first brought to her attention by local residents who sent images of the large number of dead fish to her office.
The fish were spotted on the south end of Laguna Niguel Lake, the only year-round freshwater fishing lake in South Orange County.
“I was deeply concerned and committed to finding the root cause,” Foley said in a statement.
Angler Billy Egan, who grew up going to Laguna Niguel Lake, said he saw at least a thousand fish floating dead earlier this week.
OC Parks have said the preliminary cause is most likely warm waters from recent heat waves, resulting in a drop in the level of oxygen dissolved in the water and causing some of the fish to asphyxiate, especially in the more shallow south end of the lake.
“The majority of fish at Laguna Niguel Regional Park are alive, including the catfish OC Parks stocks for recreational fishing,” Foley said.
“The lake remains open at the north end for fishing, and I’ve directed OC Parks to provide a full report for the community on the root cause of the die-off and steps to prevent similar incidents in the future,” she said. “While we investigate whether there were external factors that could have led to this die-off, such as water quality anomalies, we encourage the community to keep our office informed of potential changes in the area.”
OC Parks continues to work closely with lake management contractor, AquaTechnex, to investigate the cause, officials said.
“We understand the importance these lakes have for the community and want to stress that we are taking this very seriously,” OC Parks officials said in a statement.
While OC Parks officials could not definitively say the cause, fish die-offs can occur naturally from a combination of factors, such as changing weather, an increase in water temperature, a lower-than-average rainfall year, the presence of algae and potential equipment malfunction.
Park officials said 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.”
OC Parks has checked the equipment at the lake, officials said, and continues to monitor water temperature and oxygen levels.
Egan said he is worried about how long it could take for the lake population to rebound. He runs the professional fishing tournament WON Bass and works for the publication Western Outdoor News.
“The good news is I’ve noticed more fish swimming in the lake than not,” he said. “Laguna Niguel Lake is where I started my passion for fishing and how I ended up in the fishing industry for the past 16 years.”
He recalled a massive fish die-off at Mission Viejo Lake in 2013 that impacted the ecosystem for years, and another at Laguna Niguel Lake around the same time.
This time, it appeared more larger breeding fish had died, he said.
Most of the clean-up effort concluded Wednesday, July 23, with only a handful of fish surfacing in the following 24 hours.
To report wildlife in distress, contact the park office at 949-923-2240.
