Researchers are trying to determine what caused the deaths of three large whales found along Alaska’s coastline within a single week in late June, and whether the fatal strandings might be related to a big spike in whale deaths in the region last year.
A fin whale died in Knik Arm near Anchorage on June 22. Four days later, a humpback was found dead off Point Carolus in Glacier Bay National Park. Two days after that, another humpback was found in Turnagain Arm near Hope.
Investigators with the National Oceanic and Atmospheric Administration and partner groups have taken tissue samples from all three whales. The Glacier Bay humpback, which had been observed by scientists since the late 1960s and was nicknamed “Festus,” may provide the most clues, because researchers were able to conduct a full necropsy.
British Columbia veterinary pathologist Steven Raverty led the postmortem, and said there was no evidence of skull or other bone fractures, but there were indications the whale wasn’t healthy.
Whales usually have copepod parasites known as whale lice, Raverty said, “and this animal had probably the most abundant numbers that we’ve seen in animals that have stranded throughout the area. And it would tend to suggest that the animal may have been debilitated or there was some degree of immunosuppression.”
In addition, he said, the whale had diminished fat reserves, which may mean it wasn’t consuming enough food.
NOAA officials don’t know if these recent deaths are related to the dozens of whale deaths in the Gulf of Alaska last year. Those 2015 strandings were labeled an “unusual mortality event,” and the cause is still under investigation. It could be a difficult mystery to solve, because so many of the carcasses were too decomposed or too remote to study.
Raverty said the recent whale deaths could help researchers to better understand last year’s die-off.
“We look at these individuals that are now stranding in 2016 as a really unique opportunity to try and establish baseline health and understanding, whether there may be evidence of ship strike, infectious disease, exposure to harmful algal blooms, and these will all be put in the context of what had occurred historically, but also during the unusual mortality event,” he said.
Tissue samples from all three whales have been sent to labs for analysis, but it’s not clear when researchers will know more about how and why they died.