With tourism arrivals diving each month, another type of seasonal visitor is showing up in Hawai'i offering a bright spot for the state's top industry — the annual arrival of humpback whales.

North Pacific humpbacks spend the summer in the cooler waters from the Aleutian Islands of Alaska to the Farallon Islands off central California. During winter — roughly November to May — about 60 percent of them make the trek to the warmer waters of Hawai'i, where they mate, calve, and nurse their young, according to the Pacific Whale Foundation, a nonprofit organization based on Maui.

While whales are visible throughout the Hawaiian Islands, the Maui Visitors Bureau notes a large number of whale-watching tours, boats and interest in the traveling mammals.

"It provides a wonderful activity that people love across the board," said Maui Visitors Bureau executive director Terryl Vencl.

Neither Vencl nor the state Department of Business, Economic Development and Tourism track the number of visitors who go whale-watching while in Hawai'i.

But on O'ahu, Atlantis Navatek Cruises doubles its daily outings off O'ahu with its Whale Watch Lunch Cruise, Dec. 19 to April 12.

The 2 1/2-hour lunch cruise includes a guarantee, "See a whale or sail again for free." The cruise follows the shoreline that from Waikiki and Diamond Head toward Koko Head on East O'ahu. The price is $65 for adult visitors, with discounts for kama'aina and online purchases.

"We're able to increase our cruises to two a day for a period of about four months. It is a very important season for us," said Ken Kessler, general manager of Atlantis Navatek Cruises.

Last season, Kessler said he was aboard when a mother whale was teaching a calf to jump alongside the boat.

"For about an hour, the baby just swam in circles around the boat," Kessler said. "It was just spectacular."

Kessler said the whale sightings are usually spotty for November, and by December, there's about a 60 percent likelihood of seeing a whale.

"By mid-January, we're seeing whales every day," Kessler said.

On Maui, the whales are already showing up.

At the Pacific Whale Foundation, communications director Anne Rillero said this whale season seems to be off to a stronger start than last year's, when bad weather prevented good viewing early in the season.

"We have an annual welcome home whales event," Rillero said. "We've been seeing whales every day."

The foundation offers more tours than any Maui tour boat company, she said.

Started in 1980, Rillero said, "we've carried nearly 3 million people during that time."

She said the foundation hires all college-educated, professionally trained naturalists.

Rillero said visitors range from the mildly curious to the remarkably avid. "We have a very loyal following of people who come every year to see the whales," she said.

Those include folks who travel to Maui annually to see whales; or others who take three or four boat trips a day for the two weeks of their vacation, she said.

The foundation boat tours start at $24.95 to $31.95 for adults on a two-hour tour, with discounts for foundation members and online purchases.

Rillero said the big mammals provide an incredible experience for many.

"You hear adults squeal in delight," she said.

But she said people feel inspired by the natural wonder — especially now. "There's so much bad economic news. And people feel frightened about the future."

What does she make of the scientific indication that the numbers of whale are increasing annually, even while the number of human visitors declines?

"I think it's evidence that if you didn't have pay to come, we'd have lots of people coming here."

The visitor bureau's Vencl said whale-watching helps attract new visitors and keeps return visitors coming back.

"I do know that it resonates. It is something that people put high on their to-do list," she said.

She said people do watch from the shoreline, pulling their cars to the roadside after a telltale splash offshore. "As soon as you see that big splash, you just stop and wait and wait for the next splash. It's just amazing," Vencl said.

But she recommends a closer look. "To get the real effect, most people do plan a boat trip of some kind," Vencl said.