To a killer whale, the invisible line that divides U.S. and Canadian waters is, in theory, meaningless.

But for J-50, a malnourished young orca and part of the endangered southern resident group, where she swims next may determine whether she gets medical treatment unprecedented in the wild — or not.

On the U.S. side of the line, officials say they have boats loaded and permits in place to approach the whale and deliver antibiotics if weather allows and the animal's health warrants.

Not so in Canada, where she was spotted with her mother Tuesday near Port Renfrew, B.C., on Vancouver Island.

Fisheries and Oceans Canada said Wednesday no one has even applied to take those steps.

"We need an application and a proponent," said the department's marine mammal coordinator Paul Cottrell.

It's not clear why that hasn't happened, days into what the U.S. is calling an "emergency response" to help J-50, one of just 75 southern resident killer whales left.

But Canadian authorities insist there are risks to consider, too, when intervening with an endangered animal in the wild.

'An evolving process'

The U.S. National Oceanic and Atmospheric Administration started talking publicly about its plans last week, after overhead drone images showed J-50 in such poor condition that scientists worry she has days to live.

"It's been an evolving process, of what the best approach is," said Lynne Barre of NOAA's Seattle office.

Those plans keep changing, with revisions this morning, and Barre said emails are flying today to get applications submitted to Canada.

An experimental new technique — of feeding live, medicated fish to the malnourished whale — at first got a lot of media attention, but is last in line of possible actions.

Now, NOAA's first step after assessing the whale would be delivering antibiotics by dart-gun or pole, said Barre.

That's still not something that's been tried with a killer whale in the wild before, said Dr. Martin Haulena, head veterinarian of the Vancouver Aquarium.

"The opportunity to try new things, to be a little more proactive than we've been able to be with an ... individual of an endangered population in our own backyard is incredibly exciting."

Researchers use a pole to sample the breath of J50 on July 21, 2018, under permit number 21368. A similar pole may be used to inject antibiotics to the struggling young whale. (Katie Foster/NOAA Fisheries)

No 'smoking gun' but infection likely

A rotating team of veterinarians, including Haulena and personnel from Sea World, San Diego, are on standby at a research station in Friday Harbour, Wash., ready to act on NOAA's plan.

"We're in a really critical situation now," said Haulena, reached by phone on Wednesday.

"Other killer whales that have been in as bad a condition as this whale is in currently have not survived."

No one knows if J-50 actually has an infection that antibiotics would help, but it seems likely to be a factor, said Haulena.

Others in her pod are not so malnourished, suggesting food shortage isn't the acute problem — though prey availability is a more general threat to these endangered whales. There's also no evidence of a ship strike or other injury.

"We don't have a smoking gun here by any stretch."

Based on past deaths in captivity and the wild, the veterinary team plans to try a long-acting, broad spectrum antibiotic, said Haulena.

NOAA fisheries researchers monitoring J-50 and other endangered southern resident killer whales in U.S. waters on July 21, 2018, under permit number 21368. (Katy Foster/NOAA)

Risk to taking action: DFO

Against that backdrop — and whatever specific paperwork still needs to be submitted — Canadian officials are weighing the pros and cons of allowing anyone to interfere with an endangered animal.

"Anytime we undertake a close approach ... we'll potentially and quite likely disturb not just J-50 but the other animals around J-50," said Sheila Thornton, a research scientist with DFO.

"We don't actually have a diagnosed pathology other than malnutrition for J-50, so the treatment with antibiotics at this time is prophylactic."

Haulena agrees there are risks to consider in getting close enough to deliver a shot — within 20 metres, possibly — which is why the whales need to be in calm, inland waters to attempt an approach, whatever side the border.

However, he thinks the benefits of trying outweigh the risks, if conditions allow.

"The worst is to cause harm to another whale, so we really want to make sure everything is almost perfect."