Canadian marine mammal scientists who spent most of Saturday performing a necropsy on killer whale J-32 say the female orca had been pregnant with a full-term fetus.

The whale, nicknamed Rhapsody, was dissected as she lay on a concrete boat ramp at Bates Beach near Courtenay, B.C.

However, Department of Fisheries and Oceans spokeswoman Lara Sloan said tests to determine the cause of death were inconclusive. She said more tests will be done on the whale, which scientists say would have contributed to its pod for decades.

The loss J-32 is considered a blow to recovery efforts because there are so few breeding females.

Killer whale J-32 necropsy

The necropsy on a Vancouver Island beach took most of the day and drew a crowd. (Allen Felker/VITV.ca)

Sloan said the whale that appeared to have been dead for a couple of days was in otherwise good condition, suggesting it may not have been hit by a boat.

J-32 was from the so-called southern resident pods that ply the waters off British Columbia and Washington state. She was reported floating near Courtenay and Comox on Thursday.

The death of the 18-year-old juvenile whale, is troubling, marine mammal researchers said: It marks the fourth recent death in the endangered southern resident population.

Two of the whales, L100 and L53, are presumed to have died sometime this summer, while the calf L120 died about eight weeks ago.  Now, only 77 southern resident killer whales remain in the Salish Sea. 

Marine mammal co-ordinator Paul Cottrell said the discovery of J-32's body is heart breaking.

"It's a magnificent animal. Sixteen feet or so — so it's likely a juvenile. So, it's terrible and we want to figure out what the cause of death was here and how this animal died," Cottrell said.

According to the Orca Network, J-32 was thought to be in the late stages of pregnancy last summer judging by her wide girth, which was visible when she breached.

Most contaminated marine mammals in world

It’s always a concern to lose an individual from a small population of endangered animals, such as the southern resident killer whales, said Vancouver Aquarium marine mammal scientist Lance Barrett-Lennard

"But this is even more distressing because it was a female of reproductive age," he said. "Her probability of contribution to the recovery of this population was very high, and her years of maximum importance to the population were still to come.”

J-32 orca whale

The whale that was found dead on Thursday , J-32, had been carrying a full-term fetus, the necropsy team reported. (Ken Balcomb of the Center for Whale Research)

Vancouver Aquarium pollution researcher Peter Ross said a number of factors might have contributed to the whale's death.

"We have long been concerned about very high levels of endocrine-disrupting pollutants in these whales, reduced food supply — notably chinook salmon — and noise and disturbance,” Ross said.

The aquarium said it was Ross's research that determined the southern resident killer whales are among the most contaminated marine mammals in the world.

With files from The Canadian Press