SEATTLE — A satellite-linked tag fired into an endangered Puget Sound orca by federal biologists led to a fungal infection that contributed to the whale's death, federal scientists said Wednesday.
The National Oceanic and Atmospheric Administration Fisheries released findings into the death of a 20-year-old whale found dead off Vancouver Island in March with fragments of a dart tag in its dorsal fin. The death prompted the agency in April to temporarily halt its dart-tagging program.
Five weeks before the orca was found dead, researchers used a dart to fire the small satellite-linked transmitters into the animals to track where they go in the winter and how they find food. The transmitter is the size of a 9-volt battery and attaches to the orca's fin with two titanium darts just over 2 inches long. It's designed to detach over time and leave nothing behind in the whale.
An examination of the dead animal named L95 concluded that a fungal infection entered the orca's bloodstream, causing the whale's death, according to a report released Wednesday. A panel of five outside experts also reviewed and agreed with the findings.
Some advocates have criticized the tagging, saying it injures the orcas and there are less invasive ways to monitor the small population of whales.
Richard Merrick, NOAA Fisheries' chief scientist, told reporters during a conference call that some extenuating factors may have predisposed the whale to a fungal infection, including human error from not sterilizing the dart tag after it had fallen into the water during a failed first attempt.
The tag also hit the whale on its lower dorsal fin near significant blood vessels, broken parts of the tag also remained in the animal and the whale's health may have been compromised at the time it was tagged in February, Merrick said.
"NOAA and the biologists who work with these whales are deeply dismayed that one of their tags may have had something to do with the death of this whale," he said. "There's always a risk involved when you're conducting research on wild animals. But it's our job and our obligation to reduce that risks and that's what we'll continue to do."
The satellite tagging program will be suspended until the agency has completed its own review of the program, Merrick said.
NOAA's Northwest Fisheries Science Center in Seattle will also create an independent panel to review the need for further satellite tagging of Puget Sound resident orcas and consider alternative methods of gathering information on the whales. Recommendations are expected next year.
And NOAA's Office of Protected Resources will consider additional conditions to reduce injury or infection for all future tagging efforts on whales, dolphins and other cetaceans.
Southern resident killer whales are listed as endangered in the U.S. and Canada. Their numbers have fluctuated in recent decades as they have faced threats from pollution, lack of prey and disturbance from boats. They currently number 82 animals.
NOAA is considering whether to expand habitat protections for the orcas to include offshore areas from Washington to Northern California, and Merrick said the tagging program has been crucial to understanding the animal's habitat.
The tag has been used numerous times on whales and other marine mammals, as well as eight Puget Sound orcas.