Thursday, December 13, 2018

Missing Hawaiian humpback whales? They're staying late in Alaskan waters, but it's still not certain why.

Hawai`i's humpback whales are missing, and now there are new clues about why.

In Hawai`i as well as other southern migration areas, steep declines in whale numbers are being reported. Researchers in Alaskan waters now report that they're seeing whales that are staying in northern waters instead of migrating.

(Image: Humpback in Sitka Sound, Mt. Edgecumbe: Humpback whale flukes are visible just on the surface with Mt. Edgecumbe on the horizon in Sitka, Alaska Sunday, October 28, 2018. Credit: Seanna O’Sullivan/UAS.)
What's not yet clear is whether they will just delay migration, perhaps because of warmer conditions in areas like Sitka Sound, or whether they can't migrate because changes in food availability have deprived them of the energy for the 30-day migration.

It is also not yet clear whether the delayed or omitted migrations will impact populations. Humpback whales make the trip to southern waters to give birth to their young.

“We are concerned that the offshore warm water anomaly known as 'the blob' and other ocean conditions has had a negative impact on humpback whale prey.” said Ellen Chenoweth, a UAS Adjunct Professor at University of Alaska Fairbanks.

Researchers are trying to raise the funds to figure out what's going on, she said.  It is not just that the whales are staying longer, but there are indications they are in distress. A release from the University of Alaska Southeast suggests there's something serious going on: "The researchers noted that they are seeing fewer calves, skinnier whales and more whales staying longer into winter feeding on herring, partially migrating and returning or possibly not migrating at all."

“We would like to quantify the changes in the numbers and distribution of whales present in winter and try to get at the cause and effect. But we need more monitoring funds. This means we need gas in the boat, time to be out there later in the season and, more technicians to manage the data and document the whales and more time on the water,” Chenoweth said.

The UAS Whale Research and Education Support fund will support the research. Donations can be made here. 

The dramatic change in migration habits mars a textbook success story in whale conservation.
Humpback whale populations had been drawn so low by whaling that they were listed as endangered in 1973 under the Marine Mammal Protection Act. 
By the 1980s, numbers that winter in Hawai`i had risen from a few thousand to more than 11,000. Almost all of those whales summer in southeastern Alaskan waters where the feed on schools of capelin, juvenile walleye pollock, sand lance, Pacific herring and krill.  

The dramatic increase in humpback populations continued into the 2010s, but appeared to stop and then drop a couple of years ago.

“There is a substantial decline in the number of whales we’re seeing. But when we look very closely at least in the waters off Lahaina (Maui), which is where most of the whales congregate, that decline is very much accounted for by the drop in the number of mother and calf pairs,” said Rachel Cartwright, a California State University researcher who heads the Keiki Kohola project.

An Associated Press story reviewed the reports of declining whale numbers in the islands. 

Cartwright said that reduced food supplies in the northern feeding waters are among the suspects for the decline. Chenoweth said Alaskan fisheries officials are also concerned about the impact of feeding whales on winter populations of schooling herring.
Early indications are that the first decline in humpback whales was caused by direct killing of the animals by the whaling fleets of the 1800s and 1900s. The cause of the new decline may be indirect: the impact of climate change on water temperatures and prey availability. 

©Jan TenBruggencate 2018

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