Once again, it's that time of year when all boat operators in Hawai`i should be on the lookout for our winter visitors from the north.

No, it's not the annual migration of "snowbirds" from Canada I'm referring to, but the migration of our largest visitors, Pacific humpback whales.

Numerous humpbacks have already been sighted offshore of O`ahu and Maui, so it is just a matter of time before most of Hawaii's active boaters will become aware of their imposing presence.

And because much of our offshore waters have been designated as the Hawaiian Islands Humpback Whale National Marine Sanctuary, it is imperative that all recreational and commercial boat skippers know, understand and follow the federal and state laws concerning contact with whales.

As an endangered species, humpbacks are protected by both an Endangered Species Act and a Marine Mammal Protection Act from harm or harassment.

The most important aspect of these acts is that both make it clearly illegal to approach whales within 100 yards by any means, other than for approved scientific research.

Occasionally, I have heard a boat operator argue that his small boat could not possibly endanger such a large animal. But the humpbacks are in our warm waters primarily to breed, calve and nurse their young. Any disruption of this process is considered by authorities to be detrimental to the health and welfare of their species.

And putting a boat within the slapping range of a 40-plus-foot, 80,000-pound whale's tail could possibly be detrimental to the health and welfare of the boater, as well.

Female humpbacks that come to our waters are often here to give birth and feed their newborn calves, so they tend to stay close to shore. The comparatively shallow waters between Maui and Lana`i are particularly favored.

As these shallow waters are the same areas used by many of our recreational boaters, it is doubly important skippers are cautious, particularly when visibility is impaired by wind, rain, or sun glare. Those using personal water craft (jet skis) must be particularly careful.

Humpbacks are not particularly fast swimmers, and while they can attain speeds of 20 miles an hour for brief periods, they usually average only about three to six miles per hour. They may dive, or sound, at the sign of a speeding boat, but if they don't, the ensuing collision with a 40-ton leviathan would surely be a no-win situation for all involved.

But what if you are just sailing along and suddenly have tons of company swimming along side? The sanctuary Ocean Users Handbook points out several actions to take.

• Do not operate your boat faster than the speed of the slowest whale.
• Maneuver your boat so it will not separate whales, especially a calf from an adult.
• Do not attempt to drive or herd whales.
• Do not cut off whale from deeper water.
• Slowly increase distance from whale to the required 100-yard separation.

Boaters wanting more information, or who may witness others harassing or endangering whales are asked to call the National Marine Fisheries Service enforcement office on O`ahu at 541-2727, or the sanctuary at 1-800-831-4888.