Los Angeles Port Police are investigating a series of thefts that have marred San Pedro’s Harbor Boulevard memorials in recent weeks — leaving many in the community shocked.

Plaques, many of which are made of bronze, have been pried off several of the large and majestic sculptured monuments and tributes to the area’s fishing industry, Merchant Mariners and dockworkers, resulting in fencing going up and added patrols to try to prevent more damage and thefts.

The monuments, designed and installed through fundraising efforts in the community over many years, serve as gathering spots during annual memorials held near the waterfront. Many locals can point to family members who were listed on the original bronze pieces.

Authorities are investigating the thefts. The monuments are on Port of Los Angeles property.

“We’ve taken a very proactive role, especially at night,” Los Angeles Port Police Lt. Ryan Howley said in a Wednesday phone interview. “I don’t view this as just a property crime; it’s disrespectful and it’s in our backyard. We take this very seriously.”

The thefts of nine plaques were originally reported in November by a worker who cleans the monuments, Howley said.

Four or five additional plaques were taken about two weeks ago, he said.

“Extra heavy” patrols are keeping a watch on the area, Howley added. Further details of what is being done to prevent more damage were not disclosed as the investigation is ongoing.

“These are memorials to people’s loved ones,” Howley said, “I believe some go back to the 1800s.”

It’s not clear what materials the plaques are made of, but bronze, copper or brass are likely, as they are valuable, Howley said. They sometimes are taken to recycling yards, but not always, he said, noting some can be melted down in other ways by the thieves and those who work with them.

The thefts are part of a growing trend of taking valuable metals to be melted down and sold. More than 100 plaques were stolen just about a week ago from Lincoln Memorial Park in the 16700 block of South Central Avenue, not far from Woodlawn Celestial Gardens in Compton, which was targeted about a week earlier, according to the Los Angeles County Sheriff’s Department.

In November, Los Angeles city launched an initiative to address what officials called an “epidemic of copper theft” by cracking down on unscrupulous metal recyclers. From fire hydrants to catalytic converters and, most recently, copper wire from the lights on the iconic Sixth Street Bridge in L.A., metal theft has become a major issue.

The memorials in San Pedro, however, were personal and brought an added shock when locals began realizing what was lost.

Stephanie Mardesich of San Pedro — whose grandfather Joseph M. Mardesich Sr. was a founding partner of the French Sardine Company, later renamed Star-Kist — said she was “nearly speechless” when she saw the destruction of the fishing memorial.

“It’s absolutely unbelievable,” she said on Wednesday. “How disgusting. I’m just in shock.”

Others had similar reactions when they visited the site after hearing the news.

The International Longshore and Warehouse Union’s Bloody Thursday memorial was also hit, as was ILWU’s bronze donor plaque, which was stolen from a nearby Fifth Street spot honoring early labor activists, along with Industrial Workers of the World organizer and musician Joe Hill. That piece was found, said ILWU Pensioners President Greg Mitre, but by the time the union got it back, it had already been cut in half and was unrepairable.

“We’re considering how to replace it with another material, maybe aluminum,” he said. “We hope they won’t steal that.”

Another piece depicting Hill strumming a guitar survived, Mitre said. That one, he said, was made of “tin.”

“We were so proud to be part of it,” Mardesich said of the fishing memorial. “It just brings tears to my eyes, the devastation and the desecration, the disrespect. This is absolutely intolerable.”