Invasive Golden Mussels Found at Lake Del Valle, Prompting Boat Quarantine Order

SAN FRANCISCO—The discovery of invasive golden mussels at Lake Del Valle has prompted a 30-day boat quarantine order by park officials.

From Sep. 21, a watercraft that has been on the lake is not permitted at any other waterbody managed by the district unless it has passed a 30-day quarantine, officials said.

The lake that stretches five miles within Del Valle Regional Park near Livermore is part of the East Bay Regional Park District.

Golden mussels were confirmed present in Lake Del Valle on Sep. 11 by the Scripps Institution of Oceanography lab, which tests samples regularly collected by the Park District staff monitoring for invasive mussels since 2008, the Park District’s spokesperson Jan Vanya told The Epoch Times in an email on Sep. 23.

“To date, only golden mussel veligers have been documented in Lake Del Valle.” Vanya wrote.

The veliger larva is a typical early stage of marine snails and some bivalves after hatching from the egg capsule. These tiny, transparent larvae can drift planktonically in open water.

At Contra Loma Reservoir, the same boat quarantine procedures were implemented after golden mussels were confirmed in August 2025.

All life stages of golden mussels, including veligers, juveniles, and adults, have been documented there, Vanya said.

The District warns that boaters who have been visiting Lake Del Valle or Contra Loma Reservoir should also check requirements of the waterbodies elsewhere in the Bay Area or beyond.

The golden mussels, or Limnoperna fortunei, originated in Southeast Asia.

“If there’s a most wanted list for dangerous invasive species or damaging invasive species in California, near or top of the list are golden mussels,” California Natural Resources secretary Wade Crowfoot said in a virtual briefing on Aug. 20.

“What makes them particularly concerning is they really have an ability to quickly reproduce and spread either through connected waterways or by hitching a ride on boats and equipment,” said Kristopher Jones, who leads the Department of Water Resources’ Golden Mussel Incident Command Team, in the same virtual meeting.

The golden mussel has not been detected in reservoirs managed by the East Bay Municipal Utility District (EBMUD). The EBMUD has limited all boat launches in 2026 to prevent its spread.

“Golden mussels attach to water infrastructure in dense colonies, clogging pumps, pipelines, conveyance systems, and other critical water systems,” stated an article on the species on California Assemblywoman Rhodesia Ransom’s website.

In October 2024, golden mussels were first detected at the Port of Stockton, and they have since spread through the Delta and along the State Water Project, reaching as far as San Diego, according to Ransom.

AB 2032, or the Golden Mussel Response Act authored by Ransom, has passed and is pending California Gov. Gavin Newsom’s signature to become law.

The bill would streamline permitting processes and provide guidance to water agencies on preventing, mitigating, controlling, and eradicating golden mussels.