Wildlife officials have found a 5-month-old Hawaiian monk seal pup tangled and dead in a gill net near Waimanalo.

The news came as rare twin Hawaiian monk seal pups rescued on Midway Atoll five months ago flew home on board a Coast Guard plane after recovering on O'ahu.

Each birth among the endangered Hawaiian monk seals is seen as critical for their continued existence. And new pups are closely monitored by volunteers and wildlife officials.

Numbering just about 1,200, the seals continue to struggle for survival despite efforts to protect their main habitat in the Northwestern Hawaiian Islands.

The dead female pup had been born on O'ahu's North Shore and was relocated to Rabbit Island, where there is a resident population of the seals, said Deborah Ward, spokeswoman for the state Department of Land and Natural Resources.

The animal was found Monday in 12 feet of water after officials responded to a call from a diver, she said.

The department is seeking any information from the public on the possible owner of the net.

Proposed restrictions on gill net fishing — including bans in the nearshore waters off Maui, the west side of the Big Island and parts of O'ahu — are being reviewed by the department before receiving final approval from Gov. Linda Lingle.

Some conservationists called yesterday for the state to expedite the approval process.

"The unfortunate death of this young pup demonstrates how indiscriminate gill net fishing can be," Kim Hum, director of the marine program at The Nature Conservancy of Hawaii, a partner in the Fair Catch campaign, said in a statement. "We urge the state to move swiftly to restrict the use of lay gill nets and to consider a statewide ban."

The twin seals taken to Midway had weighed just 65 pounds and 79 pounds when they arrived at the Pacific Islands Fisheries Science Center at Kewalo Basin. They grew to 113 pounds and 131 pounds but are still about 40 pounds below normal weight and will continue to be fed at their new home.

Their 30-by-80-foot shoreline pen at Midway will be partly on the beach and partly in the water.

When the twins are released into the wild, researchers will place tracking devices on them to monitor their location and diving behavior to see if they are feeding well.