Fish Stressed and Dying in Lake Rancho Santa Margarita

Originally posted at 12:18 p.m. Oct. 3, 2014. Edited with new details.

Fish in Lake Rancho Santa Margarita are under stress and dying this week.

A note posted by Rancho Santa Margarita Landscape and Management Corp. Thursday says a lake biologist has been retained to evaluate the water condition and chemistry “to determine why some species of fish are exhibiting signs of stress.”

SAMLARC CEO Candice Fullenkamp told Patch the biologist has pinpointed the problem to foreign algae -- possibly introduced to the lake from a bird or fishing gear -- growing quickly in the early autumn heatwave.

“We jumped it as soon as we saw it yesterday,” Fullenkamp said. “The water is currently being treated now,” she said.

The die-off is unique; however, not uncommon, according to a SAMLARC Facebook post.

“Most recently the same situation occurred at Lake Laguna Niguel, the lake in Yorba Linda and the lakes in Tijeras Creek Golf Course,” it says.

A resident who asked not to be identified said the scene is hard to take in.

“It is so disheartening. I am not a vegan but I am a responsible omnivore and loathe animal suffering ... Can’t believe SAMLARC wasn’t on this sooner.”

Fullenkamp sent this technical explanation:

According to Aquatic Specialist Benjamin Chin:

Preliminary lab results indicate that the situation with the fish dying is as a result of exposure to prymnesin, a toxic compound produced by Prymnesium parvum. Prymnesium parvum is known as a golden algae and has been responsible for fish dying in lakes all over the southern United States. We are treating Lago today with an algaecide in order to prevent more fish from dying. In a few days, we will be receiving the full lab results. This will give us a clear picture of what’s occurring and perhaps may reveal some other factors that are contributing to these deaths. We are fairly confident that this golden algae is largely responsible for the deaths but we cannot say for certain that it is the only factor until we receive the full lab results.

“We ask for Lake visitors to have patience as it will take time for the treatment to be completed and take effect,” Fullenkamp said.

PHOTOS Credit: Tirzah Schmaltz