Scientists say a prominent southern resident killer whale and her young female calf are losing a troubling amount of weight.

Aerial images taken by the U.S.-based National Oceanic and Atmospheric Administration (NOAA) show J-pod orca J17 in three still images over the past three and a half years. 

The first snapshot, from September 2015, shows a robust and well-fed southern resident killer whale, but the next two stills depict a rapid loss of body fat. 

American scientists say the matriarch is now showing signs of “peanut head.” It's a term given to whales that have lost so much weight their bodies now have an hour-glass like shape. 

Healthy orcas store large amounts of fat, or blubber, in their midsections and do not commonly have an indentation between their heads and bodies.

In another blow to the endangered population, researchers say J17’s daughter, three-and-a-half-year-old J53, is also showing declines in her physical appearance. 

Southern resident killer whales, which swim in the waters off Victoria, Seattle and Vancouver, have dwindled in population to just 75 whales.

In an effort to protect the endangered species, Canada’s Department of Fisheries and Oceans has recently bolstered protections in Pacific waters.

Starting June 1, the minimum distance ships must keep from all killer whales will double to 400 metres, although commercial whale-watchers can apply for authorization to view whales other than southern residents from 200 metres away.

No vessel traffic will be allowed in “interim sanctuary zones” at Swiftsure Bank, off southwestern Vancouver Island, and near Pender and Saturna islands.

The federal department is immediately asking ships to voluntarily turn off echo sounders when not in use, allow engines to idle when within 400 metres of killer whales and, in some locations, go slow when they're within one kilometre of southern residents.

The department is also closing recreational and commercial salmon fishing in parts of the Strait of Juan de Fuca and the Gulf Islands, which will take effect after previously announced restrictions on chinook fishing wrap up this summer.

The NOAA says it will continue to use aerial drone photography to track the condition of the southern resident population this summer. Scientist also plan to collect feces in hopes of understanding more about the whales' diet, possible pregnancies, and what pathogens they may have encountered.

At the time of the last photo, J17 was swimming alongside her daughter and the rest of Jpod.

Researchers say there is no indication that they should intervene at this time.