Seven of the 76 confirmed cases of large whale entanglements documented along U.S. coasts in 2017 were in Hawaii waters, and all seven involved humpback whales, according to a recent report released by the National Oceanic and Atmospheric Administration as whale season in the state gets underway.
Researchers have also documented a decline in humpback whales visiting and are studying what the cause may be.
The U.S. total for large whale entanglements was comparable to the 10-year average between 2007 and 2016, according to NOAA, which works with fishing communities to reduce the entanglements. Of the five whale species included in the report, 49 of the entanglements occurred among humpback whales, the most of any of the species.
The seven entangled humpback whales in Hawaii represent 9.2 percent of entanglements for all reported species and 14.3 percent of all entanglements for the species.
While seven seems like a small number, Ed Lyman, NOAA’s large whale entanglement response coordinator, said the number of humpback whale entanglements in Hawaii waters has generally been on the rise for the past 15 years. Looking at seasonal numbers, which span November to May, offers a better overall picture, he added.
During the humpback season from November 2017 to May, Lyman said, there were 14 cases of humpback whale entanglements around the main Hawaiian Isles, which was more than in November 2016 to May 2017, when there were four. In the season prior to that, November 2015 to May 2017, there were six entanglements, he said. However, in the 2014-2015 season there were 13 confirmed humpback whale entanglements, which is comparable to the 2017-2018 season, he said.
Unanswered questions
The big question is why humpback entanglements appear to be on the rise when there were fewer sightings of them in Hawaii waters.
“Everything matches except for Hawaii this past season,” said Lyman.
One theory is that some whales in Hawaii came from feeding grounds in British Columbia, where there was a higher than average number of entanglements, rather than Alaska. At least three of the entangled whales had gear from British Columbia, he said.
NOAA reported a decline in whale sightings over the past three seasons starting as early as 2015, prompting researchers in late November to hold a first-of-its-kind meeting on Oahu to compare notes and search for possible causes of the downward trend.
Every winter, humpback whales migrate from Alaska to the warmer, shallower waters of Hawaii to mate, give birth and nurse their calves.
Many researchers agreed that the humpback whales’ feeding grounds in Alaska may have been affected by warmer water temperatures, causing them to seek food elsewhere or preventing them from making the journey to Hawaii.
“There was broad agreement that whale counts from Southeast Alaska, Prince William Sound and many parts of Hawaii have been trending down for the past four to five years and that these decreases include both adults and calves,” said NOAA whale research coordinator Marc Lammers in an email. “There is a strong suspicion that the downward trend is linked to changes in prey availability somehow.”
Important questions still remain, he said, about whether these decreases reflect changes in where humpback whales are going to feed and breed, or an actual decline in the population, and whether it is part of a broader trend. Researchers will continue coordinating their study of whale movements and environmental factors possibly contributing to the changes.
“I think the bottom line is that we managed to connect a few pieces of the puzzle but that we are still a ways away from solving it,” he said.
Dangerous work
Given the size and strength of large whales, the work of disentangling them out on the open ocean is dangerous, but NOAA trains a network of individuals from various industries, nonprofits and academic groups to disentangle the whale as well as document its condition and assess its health.
Last year a Canadian responder died during a rescue operation of an entangled North Atlantic right whale in the Gulf of St. Lawrence. NOAA temporarily suspended large whale entanglement response in the U.S. while officials investigated the incident, and developed an online course every responder is required to take to prevent future accidents.
Lyman said drone technology has improved the ability of teams to venture out and disentangle whales from nets. They offer a bird’s-eye view of the marine mammal first so teams can devise a plan before their approach. They also offer valuable information on the whale, its condition and how it is entangled.
As for this season, the whale-watching community is eager to see whether sightings will continue to diminish.
“We’re all waiting to see how it’s going to play out,” he said.
NOAA report highlights
>> The five most frequently entangled large whale species in 2017 were humpback whales, gray whales, minke whales, blue whales and North Atlantic right whales.
>> Of the 76 confirmed cases, 70 involved live animals, six were dead.
>> The entanglements were confirmed in the waters of 13 states along U.S. coasts except the Gulf of Mexico.
>> The humpback whales were entangled the most often.
>> Approximately 70 percent of the whales were entangled in fishing gear.
>> The Large Whale Entanglement Response Network hotline in Hawaii is 888-256-9840.
Source: NOAA Fisheries, National Report on Large Whale Entanglements Confirmed in the U.S. in 2017
