PROVINCETOWN, Mass. (AP) – An endangered North Atlantic right whale was seen this week entangled in marine line in Cape Cod Bay, but rescuers have been unable to reach it.

Fishing gear entanglements and ship strikes are the greatest manmade threats to the right whale, which scientists estimate have a worldwide population of about 350.

The entangled whale is a 16-year-old female that’s had two calves and is at the start of her breeding years, so losing her would be “a blow to the population,” according to Greg Krutzikowsky, director of the disentanglement program at the Center for Coastal Studies.

The whale was first spotted tangled in green marine line about 20 miles southeast of Chatham on March 9. It was spotted again on Wednesday about 14 miles southwest of Provincetown. The whale dove so frequently that rescuers from the center were unable to free it or attach a device that could track it, Krutzikowsky said. Rescuers were unable to search Thursday because of inclement weather.

“We’re sort of waiting until it gets seen again,” Krutzikowsky said. Last year, the National Marine Fisheries Service proposed a mandatory speed limit to prevent ship strikes on whales, but the rule has been not finalized.

Last week, The Humane Society of the United States and The Ocean Conservancy sued NMFS, saying it has illegally failed to protect three endangered species, including North Atlantic right whales, from fishing gear entanglements.