10/06/2011 10:13 pm ET Updated Dec 06, 2011

Salmon Theft On Massive Scale Baffles Marin County Authorities (VIDEO)

In one of the largest animal thefts in U.S. history, saboteurs released 40,000 juvenile Chinook salmon late Monday night from Tiburon Salmon Institute holding pens at the San Francisco State Romberg Tiburon Center for Environmental Studies.

Officials believe the theft to be either the work of animal rights activists or local fishermen hoping to use the salmon as bait for larger fish.

The thieves accessed the holding pens by boat and cut the ties connecting the nets enclosing the salmon inside the pen.

"[They] came along with essentially what are wire cutters to do this," Tiburon Salmon Institute Executive Director Brooke Halsey told the Marin Independent Journal. "It was purposeful. Someone knew what they were doing."

Ironically, the fish were to be released into the wild only weeks later. The salmon were part of an educational program the Tiburon Salmon Institute was running in conjunction with Petaluma's Casa Grande High School where students tended to the fish and eventually released them into the bay. A ceremony for the students to release the fish was scheduled for October 30th.

ABC-7 reports:

Greg Gillis, 17, says they were his babies. He and his classmates at Casa Grande High School in Petaluma were responsible for every stage of their lives.

"We took care of them, we spawned them from mother and father fish and raised them from before they were even fish," said Gillis.

A post on PETA's website applauded the theft, saying that salmon held in crowded conditions similar to the ones at the institute often suffer from severe injuries and are easily susceptible to flesh-eating parasites.

Whoever released the salmon depleted two-thirds of the institute's current stock; the remainder will be set free during the event with the students at the end of the month.

The Tiburon Salmon Institute has hatched and released up to 50,000 salmon into the San Francisco Bay every year for over three decades.

Releasing salmon helps the species' numbers at a sustainable level. Over the past few decades, the number of salmon swimming to and from their hatching grounds in the Sacramento-San Joaquin Delta have dwindled due largely to water diversion to California's Central Valley.

The only animal liberation effort in recent memory with a similar scope occurred in 2000, when activist from the Animal Liberation Front released a herd of 14,000 mink from a farm in New Hampton, Iowa.