Researchers want to use trained stellar sea lions in the ocean to study the endangered species, but the proposal is raising interest and controversy.

Scientists across the Pacific Northwest have been studying stellar sea lions in captivity and in the wild for years. The world population of the marine mammals has dropped from more than 300,000 to fewer than 100,000.

Stellar sea lions are listed as an endangered species in the Gulf of Alaska and Aleutian Islands.

Sitka

Sitka is a six-year-old stellar sea lion. Although visitors can usually see her at the Vancouver Aquarium, for the past four months she's lived at a marina in Port Moody.

Sitka is the focus of a unique open ocean study, according to trainer Vance Mercer.

"I look at these animals as ambassadors to their species," said Mercer. "What we learn and what I am doing with them is very important to the wild population."

Annelise Sorg

Some scientists believe stellars are vanishing because their food source is disappearing. That's where trained sea lions like Sitka come in.

"With these animals here, we will be able to learn how much energy they require to find food," said Andrew Trites of the University of British Columbia.

Trites said they hope to determine if there are depths where it is too difficult for stellars to find food. Better calculations will help researchers determine how the manage fish resources more wisely.

The project is not without controversy.

"One has to question why the sea lions are at the Vancouver Aquarium to start with," said Annelise Sorg of the No Whales in Captivity Coalition. "Is this really for research? Why are they not being re-introduced into the wild?"

The coalition says when the first batch of pups were captured, they were supposed to be re-introduced into the wild after three years of experimentation.

Instead, the sea lions have been put on display at the aquarium, said Sorg.

Trites dismisses the coalition's arguments, saying the project stands on its own merits.