Council members reported to the Laguna Niguel City Council on Aug. 19 that findings from a recent town hall indicate low dissolved oxygen, amplified by hot, overcast weather, is the likely cause of a recent fish die‑off at the Laguna Niguel Regional Lake.
Council Member Otto, Mayor Pro Tem Johns and Mayor Genway said the town hall convened county staff and contractor Science Aquatech, represented by Terry McNabb, who explained that a sequence of hot days followed by overcast conditions can heat surface water, then limit oxygen replenishment and trigger fish mortality. Council members said most of the fish that died were trout that moved up into the creek seeking oxygen and perished there rather than in the lake.
Council members said water‑quality testing did not detect fertilizers, poisons or pesticides at levels of concern. The county discussed operational changes including keeping aerator replacement parts on hand, ensuring power access for aeration systems, and increasing contractor monitoring visits to the lake to reduce the chance of recurrence.
Council Member Otto and Mayor Pro Tem Johns urged residents to monitor county updates and said the county has a longer‑term plan that may include improvements to the lake’s concession and infrastructure in the capital improvement program.
Why this matters: The lake is a neighborhood amenity used for recreation and habitat; mass fish mortality raises public‑health and ecological questions and prompted a county response to reduce the risk of future events.
Additional details: Council members encouraged residents to visit ocparks.com for updates and said county staff are analyzing operational and capital measures, such as on‑site aeration spares and more frequent contractor visits.