Will there be more humpback whales traveling to Hawaii this winter?
Researchers are anxious to find out, given that they observed a recovery in whale sightings in the last season following several years of decline.
“This past year, by all counts, from researchers monitoring the humpback whales in Hawaii, the numbers seem to have increased again to at least the two years prior,” said Marc Lammers, research coordinator of the Hawaiian Islands Humpback Whale National Marine Sanctuary. “It’s kind of given us some cautious optimism that perhaps we’re seeing a little bit of a reversal in the trend. However, it’s a little too early to say for sure.”
The Central North Pacific stock of humpback whales that migrates from Alaska to Hawaii’s warmer waters to mate, calve and nurse their young has been estimated at roughly 10,000 individuals. The massive marine mammals, which can grow to 60 feet in length and weigh 40 tons, arrive as early as October and stay as late as May, with peak activity occurring from January to March.
There are some variations, and last season January got off to a slow start, then took off in February, according to Lammers.
“By all accounts February was a strong month,” said Lammers, who is based in Kihei, Maui. “That continued on through March, and in April the numbers were decreasing, but relative to the previous two to three years, we still had a surprisingly large number of whales, particularly mothers and calves.”
Many humpback mothers and calves that prefer the warm, shallow waters around the four islands of Maui County lingered in Hawaii late last season, and Lammers is eager to see whether those calves make it back this season.
Additionally, there was an uptick in whale chorusing levels last season, according to Lammers, who specializes in acoustic monitoring, signaling a greater number of humpbacks visiting the Hawaiian Isles.
A dip in the number of whale sightings, which started in 2015 and lasted through 2018, created enough concern among researchers that they convened for a first-of-its-kind conference in Honolulu in late November to search for clues to the cause of the decline.
One major theory was that the humpback whales’ feeding grounds in Alaska were affected by warmer ocean temperatures, disrupting their main food source, mostly shrimp-like krill and small fish, and preventing them — mothers and calves, in particular — from consuming enough fuel for the 3,000-mile migration to Hawaii.
“The fact we saw an increase in whale numbers this past season is either a sign that trend has reversed itself and now they’re going back to a more normal pattern of migration and returning to same feeding areas to where they had been feeding traditionally,” Lammers said. “The other possibility, though, is we saw a one-year blip.”
It could also be part of a natural up-and-down cycle, according to Ed Lyman, the sanctuary’s natural resources management specialist. Then again, the whales could have simply been spending their winters somewhere else.
He, too, confirmed a “bit of a bounce-back” in sightings last season.
More whales, more problems
Unfortunately, more whales around the Hawaiian Islands also means more reports of entanglement in abandoned fishing gear, ropes and other debris, according to Lyman, who is also the sanctuary’s large whale entanglement response coordinator.
Entanglements have been on the rise overall when looking at long-term data over more than 15 years.
In the 2018-2019 humpback whale season, there were 11 confirmed reports of whale entanglements, representing at least nine different humpbacks, which was close to the average. Seven of the humpbacks were reported off Maui.
During some of the seasons with fewer sightings, there were only four to six reports, but one year there were more entanglements and fewer sightings.
The whale response network team, which includes the National Oceanic and Atmospheric Administration and various agencies, mounted five responses — all on Maui — for three of the entangled whales last season and was able to free two of them from more than 400 feet of gear.
Both entangled whales were juvenile humpbacks. One had a mouth entanglement from a Dungeness crab trap from British Columbia. The other was entangled in a giant king crab style of trap from Alaska and had more than 400 feet of line trailing behind it.
For the first whale, the team was not able to get the gear off, but made some cuts to the lines. For the second whale, the team was able to cut most of the trailing line.
Tour boats had reported both cases and took turns tracking the entangled whales — a good example of teamwork, according to Lyman.
Blake Moore, director of commercial operations for the Maui-based Pacific Whale Foundation, is feeling optimistic about this season.
“Moving into this year, we do anticipate that number to be similar or even higher,” he said. “We’re anticipating a great whale season in 2020 and a great opportunity for residents and tourists alike to find their way to the ocean and see these whales.”
For the past 10 years, the foundation’s first whale sighting has occurred in October and as early as Oct. 5. Back in 2000 the first whale was spotted even earlier, on Sept. 16.
As a tour boat operator, the PWF’s crews are the “eyes on the ocean” seven days a week, year-round. Part of its mission is to not only conduct research, but inspire others to love and protect whales and become stewards of the ocean.
This year the PWF is participating in several beach cleanups for International Coastal Cleanup Day on Saturday, and it launched a ReTHINK campaign encouraging people to consider how they can reduce their use of single-use plastics in their daily activities.
Mystery surrounds activity
The Central North Pacific humpback whales in 2016 were removed from the U.S. endangered species list after the government determined the population had recovered in numbers.
Continued threats facing the whales include vessel strikes, vessel-based harassment and entanglements, along with changes to their habitat and ocean environment.
In 2015 there were several ocean-warming events that included El Nino and an ocean heat wave called “The Blob.”
In July of this year, NOAA noted the warmest month on record for Alaska, at 58.1 degrees Fahrenheit, and above-average sea surface temperatures across Hawaii. Scientists are bracing for a severe coral bleaching event similar to the one that occurred in 2015. There is also speculation that a second round of “The Blob” is imminent in the Pacific Ocean.
“These kinds of oceanographic heat waves, as we’re calling them, are projected to become more frequent,” Lammers said. “We need to understand how they’re affecting our humpback whale population.”
Scientists cannot assume the challenges the humpback whale population faced a few years ago have gone away, he said. Given that the marine mammals cross almost the entire North Pacific Ocean, they are a reflection of the ecosystem’s health.
And yet, much of how the humpback whales spend their time remains a mystery.
This year Lammers’ team will conduct vessel-based whale surveys to complement data from the recording devices placed underwater around the main Hawaiian Isles.
In April, Lammers had the rare opportunity of going to the Northwestern Hawaiian Islands, where he observed quite a number of humpback whales on a journey just past French Frigate Shoals. That led him to wonder how those whales are connected to the ones that frequent the main Hawaiian Isles.
The team has deployed several acoustic recorders there to collect data and is now trying to match photographs of flukes with its database.
“We’re very curious to see how this next season plays out,” Lammers said. “It will be very telling as to whether the improvement we saw last year will present a return to normalcy or whether it’s just a kind of little bit of uptick in a still declining trend.”