Vandals again cut the ties that held the nets containing the 8- to 10-inch salmon in place. The salmon were being kept in three pens that measure 25 by 16 by 8 feet.
The fish were being raised as part of an annual restoration project run by the Tiburon Salmon Institute in partnership with the San Francisco Tyee Club.
Some of the 40,000 salmon released in the first crime had been raised from eggs by students at Casa Grande High School in Petaluma. The 20,000 salmon that were left were raised by volunteers at the Feather River hatchery.
All of the salmon were scheduled to be released into the San Francisco Bay in a ceremony on Oct. 30.
The latest incident happened late Friday night or early Saturday morning, said Al Nichelini, an employee of the Tiburon Salmon Institute.
Brooke Halsey, the institute's executive director, found the fish missing Saturday morning, Nichelini said.
The previous vandalism occurred between 9 a.m. Oct. 3 and 9 a.m. Oct. 4.
Casa Grande High School teacher Dan Hubacker, who advises the students involved in raising the salmon, said it cost thousands of dollars to acquire the fish eggs, raise the salmon and tag them before release.
He said some of his students have already learned about the latest vandalism, and that he will break the news Tuesday to those who haven't heard.
"We need donations for security," Hubacker said.
The Marin County Sheriff's Office is investigating the vandalism.
No one has claimed responsibility for the crimes, but Peter Young, a spokesman for the Animal Liberation Movement, responded to the vandalism in a posting on the online journal "Voice for the Voiceless."
"Those who held these fish captive are still complaining, as though they every (sic) had a right to keep 60,000 fish in nets to begin with," Young wrote.
"Anyone who keeps any animal in a cage anywhere should be reminded: 'The ALF (Animal Liberation Front) is watching.'" he said.
He said it has not yet been confirmed that the salmon releases were the work of an animal liberation group.