Hawai'i whale-watch captains will be discouraged this season from following humpback whales, a procedure which could cause the whales to think they're being stalked by a predator and flee instead of giving humans a close-up look.

"In the past, we've said, 'Approach from the rear or the side, as long as you stay 100 yards away,' " said Jeff Walters, co-manager of the 1,400-square-mile Hawaiian Islands Humpback Whale National Marine Sanctuary. "Having spoken to the experts, we think that following from behind may make the whale feel it's being stalked and could elicit predator fear."

One veteran whale-watch captain said last week at a Kaua'i workshop of commercial boat operators that he's gotten better success by staying twice as far as the federally mandated 100-yard distance, Walters said.

"He follows slowly, cuts his engines 200 yards away and puts a microphone in the water to listen," Walters said. "Stopping farther off, the whales get a chance to get used to them, and sometimes they'll decide to come closer to the boat."

It's that kind of information that officials at the sanctuary, which is co-managed by the state Department of Land and Natural Resources and the National Oceanic and Atmospheric Administration, hope will be shared at upcoming workshops "to help everyone learn what works and what doesn't," Walters said.

The statewide workshops are aimed at the 150 or so commercial tour operators that cruise the sanctuary to reinforce federal regulations and refine techniques to prevent mishaps involving humans, boats and the 45-ton humpbacks.

Workshops were held this week in Hawai'i Kai, Kapolei and Kailua, Kona. The final workshop is Tuesday on Maui. No reservations are required to attend.

Last year, six whales were struck by vessels. Since 1975, there have been 38 confirmed whale strikes.

"No matter what kind of vessel you operate, these workshops are a great opportunity to learn about the latest collision-avoidance guidelines and recommendations," Laura H. Thielen, DLNR chairwoman, said in a statement.

Much of the information is technical, like keeping engines running rather than shutting them on and off or shifting from forward to reverse, which can produce sounds that may scare whales away.

Some of the information merely emphasizes common sense.

"Definitely don't try to cut a whale loose that's been entangled in fishing nets or lines," Walters said. "Call the experts."

At least seven humpbacks were reported entangled in debris last year and four were freed, Thielen said.

At each workshop, Ed Lyman, marine mammal response coordinator for the Hawaiian Islands Humpback Whale National Marine Sanctuary and a licensed captain, will present a new map of whale populations across the state and give tips on how to spot whales at sea.

Much of the advice for boat captains, like not following directly behind whales, already has been adopted by some operators, Walters said.

"A lot of the policies are already followed by the whale- watch community in Hawai'i," Walters said. "We want to learn from each other. And it'll be good to help the whales out."

Reach Dan Nakaso at dnakaso@honoluluadvertiser.com.