A record 57 tons of marine debris was captured by this year’s annual National Oceanic and Atmospheric Administration cleanup expedition to the Northwestern Hawaiian Islands, including the largest net ever removed from the area, an 11.5-ton monster large enough to fill up a 20-foot shipping container.

Crews aboard the NOAA research vessel Oscar Elton Sette began offloading their haul of derelict fishing gear and assorted junk Tuesday following a mission with stops at Pearl and Hermes Atoll, Maro Reef, Lisianski Island and Midway Atoll.

During the 33-day expedition, crew members not only removed debris hazardous to monk seals, turtles, seabirds and coral reefs, but rescued three entangled green sea turtles and removed two 30-foot Japa­nese boats that had been swept away by the 2011 tsunami.

"We saw everything you can imagine, from light bulbs to plastic floats, televisions and tires. It’s amazing how it gets up there and gets on the beaches and the reefs," said Mark Manuel, the mission’s scientist-in-charge.

The turtles?

"That was a bonus," he said. "We probably got to them just in time. Who knows how long they would have stayed alive if we didn’t get to them? But we were just fortunate they were able to swim off on their own after cutting the nets."

More than 904 tons of marine debris has been removed from the Northwest Hawaiian Islands since the annual cleanup was established in 1996, officials said.

As they have in the past, the nets this year will be recycled and converted to electrical power on Oahu as part of Hawaii’s Nets to Energy partnership with Covanta Energy and Schnitzer Steel Hawaii Corp.

This year’s expedition hauled in 300 to 400 sizable nets, but the biggest prize came from the reef at Pearl and Hermes Atoll. Manuel said the enormous net was found in water 15 to 16 feet deep, filling an entire water column from the surface to the bottom. It took four days to cut through the net and another day or two to prep it for hauling away, he said.

"It was too heavy to bring it in on our small boats, so we had to rely on the ship boats to tow it back to the ship," he said.

The massive net was actually discovered by a NOAA ship last year. The ship didn’t have the capability to remove the net then, so a transmitter was attached to mark its location. Unfortunately, a winter storm washed the transmitter away.

"We were lucky enough to roll up on it," Manuel said, adding that it was identified from photos.

The net, they discovered, had moved along the seafloor about 3 miles.

"It destroyed everything in its path. The sheer mass of it was that large," Manuel said. "We did a general damage assessment, and pretty much everything in that vicinity within 20 meters to 30 meters was just pummeled to pavement."

The trawl seine net, equipped with floats, had no identifying marks pointing to its owner, Manuel said, but it was likely accidentally lost at sea by a fishing boat somewhere on the Pacific Rim — although not from Hawaii, where fishermen don’t use such nets.

David Swatland, acting superintendent of the Papahanaumokuakea Marine National Monument, said he is thankful for the annual marine debris cruises, but the truth is they make only a dent in the accumulation of rubbish in the northwestern islands.

It is estimated that anywhere from 50 to 100 tons of debris annually collect at the group of islands, which acts like a comb against the natural ocean circulation.

"We really don’t know what’s up there," Swatland said. "We don’t have the money or the resources to conduct a really comprehensive marine survey."

Swatland said the annual NOAA cruises concentrate on removing the highest-priority debris: the fishing nets that threaten marine life.

"There are tons of other things collecting up there: plastic bottles, TV screens, buoys, all kinds of things. One hundred percent of marine debris comes from somewhere else. It’s kind of frustrating for us to have this beautiful pristine place, one of the last places on Earth that existed much like it did before human contact, and it’s got trash all over it, and it’s all from somewhere else," he said.

Swatland added that "until people start reducing the stuff they use and change their consumption, not use so much plastic and find better ways to dispose of that stuff, it’s going to keep accumulating."