Beachgoers discovered an endangered 9-year-old Hawaiian monk seal that had drowned after it became entangled in a fishing net in waters off the Leeward Coast.

RW08, also known as Kerby, was found dead in the ocean Friday morning.

“When they found him he had already drowned,” said Charles Littnan, lead scientist of the Hawaiian Monk Seal Research Program.

An investigation has been initiated into the seal’s death.

Scientists with the monk seal program, part of the National Oceanic and Atmospheric Administration, responded to the call of an entangled monk seal at about 9 a.m. Friday.

When they arrived, beachgoers already had disentangled the monk seal from the net while the mammal was in the water. After they brought the net to shore, beachgoers along with the marine mammal response team attempted to recover the carcass from the water, but another monk seal showed up and “was behaving quite defensively,” Littnan said.

The monk seal’s aggressive behavior and rough ocean conditions hindered efforts to retrieve RW08. Since then lifeguards, staff of the monk seal research program and volunteers have been monitoring the shoreline and searching the waters for the carcass.

“There’s still a chance we might find him,” Littnan said.

Since 1994 five monk seals have died due to entanglements.

Of RW08’s death, Littnan said, “This is an accident. Nobody intended for this to happen.”

Nevertheless, it serves as a reminder for the public to review best practices on the proper use of fishing nets. Littnan noted stringent regulations are in place to protect monk seals, turtles and other species from suffering the same fate.

According to the state Division of Aquatic Resources, these rules apply:

>> It’s unlawful to leave a lay net unattended for more than a half-hour.

>> All threatened or endangered species must be released from entanglement.

>> Lay nets may not be used for more than four hours during any set. After the end of one set, the same lay net may not be used again within 24 hours.

“If people stay committed and follow those rules, that would go a long way to avoid situations like this in the future,” Littnan added.

In the last several years, Kerby played an important role in scientists’ research of a monk seal’s diet and behavior. RW08 was born in April 2008 on Rabbit Island. Scientists had attached a small video camera to his back with a global positioning system to record the seal’s movement, behavior and fisheries interactions.

Littnan said Kerby had been hooked at least three times, twice in 2009 and once in 2011.

There are approximately 1,400 Hawaiian monk seals — 300 in the main Hawaiian Islands and 1,100 in the Northwestern Hawaiian Islands.

Anyone with information on the fatal monk seal entanglement involving RW08 is urged to call NOAA’s Office of Law Enforcement at 800-853-1964. The public also may call the marine mammal response line at 888-256-9840 to report a hooked or entangled seal.