It’s a fishy mystery.
Hundreds of fish turned up dead at Lago Santa Margarita lake recently. And it isn’t the first time this has happened.
For years, the city of Rancho Santa Margarita has been trying to prevent algae blooms – and help the lake’s fish thrive – at the popular community fishing spot.
The latest “fish kill” of about 400 was first documented on Sunday, Nov. 1, when several small fish in the lake were displaying signs of stress in the deeper areas of water, an announcement posted to the Rancho Santa Margarita Landscape and Recreation Corporation’s website said. Officials referred to the announcement when reached for comment.
Caretakers of the Lago Santa Margarita – including the management company FirstService Residential, the board of directors and the lake service provider Lake Management, Inc. – coordinated a plan to determine the cause and limit the number of fish affected.
Based on onsite water testing, visual assessment and historic data, it was determined a golden algae bloom occurred in the lake last weekend, possibly caused by the combination of colder weather, which altered the water chemistry, as well as debris from recent fires, the SAMLARC update online said.
Since the initial report, water quality has improved, indicating the lake is stabilizing, SAMLARC officials said online, explaining that golden algae – its scientific name is Prymnesium parvum – grows in many man-made, freshwater lakes as an “interwoven member of the ecosystem.”
“As with most species, golden algae cannot be completely eradicated from an environment; however, management strategies may mitigate its activity.”
The bloom mostly killed smaller fish in the lake, with less than 200 catch-sized fish turning up dead. There was no impact to other nearby wildlife such as birds, turtles or catfish and crawdad species, officials said.
The popular fishery draws boaters and anglers and is stocked regularly with bass, bluegill, carp, catfish and more. There’s no swimming allowed in the lake. A one-mile walking trail borders the shore.
In the upcoming weeks, more water sampling will be done, custodial service will be increased around the lake and water patrols deployed to assess fish activity and collection of fish and debris.
The incident was much smaller than others that occurred in previous years, said George Blair, assistant general manager of SAMLARC.
A lake ecosystem restoration plan the last few years addressing the water quality, included installing floating botanical islands to absorb excess nutrients in the water to decrease the supply for golden algae to survive on. Aerators help assist water turnover, improve oxygen levels and reduce sediment build-up.
