Two malnourished monk seal pups were rescued during the latest mission to the Northwestern Hawaiian Islands by the research ship Hi‘i­ala­kai in its efforts to protect the endangered species.

The ship and crew working for the National Oceanic and Atmospheric Administration docked in Pearl Harbor on Monday after a 21-day voyage.

As part of its voyage, 14 researchers were deployed on five remote islands to monitor and help to sustain the monk seal population. They will remain there over the next four months.

Stacie Robinson, a NOAA official with the Hawaiian Monk Seal Research Program, said the 14 researchers will be doing population counts, disentangling monk seals from marine debris and moving the young seals to areas where there are fewer sharks. They were dropped off with camping provisions to conduct work on French Frigate Shoals, Laysan Island, Lisian­ski Island, Kure Atoll and Pearl and Hermes Atoll.

Robinson said the camping missions have been occurring since the early 1980s, contributing to an understanding of the seal population.

The population of Hawaiian monk seals, or Mona­chus schauinslandi — one of the rarest marine animals in the world — has been on a decline from as many as 1,600 a decade ago to as few as 1,100 today, according to scientists.

The ship dropped off the two Hawaiian monk seal pups at the Marine Mammal Center’s Ke Kai Ola hospital in Kona, where they are expected to be nursed back to health. The monk seal pups, a female and a male prematurely weaned, were found on Pearl and Hermes Atoll. Scientists said the pair would have died without intervention.

The Marine Mammal Center, including a pool designed to help in the recovery of Hawaiian monk seals, opened last year.

NOAA and the center enjoy "a good partnership," Robinson said.

Federal officials also worked with Sustainable Coastlines Hawaii on a pilot project to pick up terrestrial marine debris and plastic from beaches at five islands and atolls. On Ford Island, where the Hi‘i­ala­kai docked upon its return, crews also dropped off some 5,000 pounds of marine debris.

"This is the start of a research project that will identify types and sources of debris and estimate accumulation rates," said NOAA spokes­woman Wende Goo.

Kahi Pacarro, executive director of Sustainable Coastlines Hawaii, said the trip to the Northwestern Hawaiian Islands helped to broaden his understanding of the importance of developing nontoxic byproducts.

Pacarro, who was on his first trip, said he saw that many of the young albatrosses at Midway had ingested plastic. The rib cage of one dead chick was filled with plastic, he said.

He said that in some places, animals are nesting in mounds of debris.

Pacarro said debris arrives on the islands via the Pacific gyre garbage patch between Hawaii and Cali­for­nia.