A four-year study using drones has found startling evidence that southern resident killer whales are thin and malnourished.

B.C. scientists say what they captured from above points to trouble below.

Days after returning home from the research mission, early observations show orcas are falling behind their thriving seal-eating cousins.

Experts are now armed with proof southern residents are malnourished, especially mothers and their young.

"If we don't address this issue of nutritional availability, of fish availability to whales I think there is a good chance we could lose them,” said Vancouver Aquarium’s orca expert Dr. Lance Barrett-Leonard.

At its core, the study points out a lack of fish food for the whales.

"Chinook [salmon] are of year-round importance to them and really I think that’s probably the fundamental next step in their conservation,” said marine zoologist Anna Hall.

While a lack of food is a major concern, experts say the bigger issue may be humans.

Canadian and U.S. experts watched as orcas successfully tracked fish, but saw the animals were at times hampered by vessel noise and traffic.

“There is enough salmon in the ocean right now to support this population we believe, but the problem is that it’s not concentrated in places where the whales can efficiently get at it,” said Barrett-Leonard.

The study is still in the early stages, but scientists hope to share published research when orca experts and federal government officials meet in Vancouver next month.

With a report from CTV Vancouver Island’s Scott Cunningham