The U.S.'s Center for Whale Research says an iconic orca named J28 has died after months of losing weight, which could also bring about the death of her latest offspring, J54, who was born in late 2015.

On Friday, the centre announced the death, which comes less than a year after the two cetaceans were celebrated as being part of eight calves born in 2015.

It was a baby boom for the animals and scientists said at the time it had put the population of endangered southern residents, "back within its normal birth rate."

Since her birth in 1992 or 1993, J28 was easy to spot in the inshore waters of the Pacific Northwest, due to a nick on her dorsal fin.

VIDEO | Center for Whale Research news conference announces death of J28:

The centre has not been able to recover J28's carcass but hopes to in order to determine the cause of her death and the number of pregnancies she's had in her lifetime.

"J28 was noted to be losing body condition in January 2016, presumably from birthing complications and by July was clearly emaciated," said the centre in a news release. The centre also said it believes the animal died in the Strait of Juan de Fuca sometime between Oct.16 and Oct.18.

J28 gave birth to J46 in 2009 but lost a baby in 2013.

The centre says that due to J28's death, J54 will most likely not survive because he needs his mother's milk to survive and has gone too long with inadequate nutrition.

J54 southern resident killer whale dorsal rakes

The Center for Whale Research says J54 has tooth rakes from sister J46 who was trying to help him to surface when he was in delirium on 23 Oct. 2016, most likely caused by malnutrition. (Mark Malleson)

J28 is survived by her mother, (J17) two sisters (J35 and J53), a brother (J44), a daughter (J46) and a nephew (J47).  

Sister trying to save J54

"Her daughter and her oldest sister (J35) are attempting to care for the orphaned calf," said the centre in a statement.

"His sister, J46, had been catching and offering salmon to her mother and little brother for several months while mom was ill, but that was simply not enough nutrition provided to three whales by one little female, no matter how hard she tried."

The centre says the pod is now reduced in size to 80 animals, down from 85 in January, 2016.

At a news conference announcing the death, the Center for Whale Research asked for changes to dams it says are keeping chinook salmon from getting into the feeding grounds of southern resident killer whales.

Orca J54 and J28

Newborn orca J54 swims alongside its mother, J28, in Haro Strait after it was born in December, 2015. (Dave Ellifrit/Center for Whale Research)