IntroductionHumpback whales (Megaptera novaeangliae) annually migrate from their summerfeeding grounds off southeast Alaska to winter in waters off the HawaiianIslands, Baja California Sur, Mexico and northern Japan (Baker andDarling). The number of humpback whales in the Hawaiian waters generallypeaks from mid-February through mid-March ( Baker & Herman, 1984). Calvingand breeding is an important function of humpback whales while wintering atlower latitudes ( Herman and Herman et al., 1980). The presence of thesewhales has spawned a popular and rapidly growing whale-watching industry.Whale watches are undertaken with a wide assortment of vessels. Because ofthe ever-growing number of boats involved, concerns are often expressed bythose in the whale-watching industry, environmental groups and governmentalagencies about the effects of vessel disturbance on the whales ( Green,1998).Humpback whales have been observed to react to approaching boats in anumber of different ways ranging from approach to avoidance. On rareoccasions, humpback whales have been observed charging towards approachingboats and screaming underwater (Payne, 1978). Bauer (1986) and Bauer andHerman (1986) found that respiration rates, diving, swimming speed, socialexchange and aerial behaviors correlated with vessel numbers, proximity,speed and direction changes. They reported that humpback whales generallyattempted to avoid vessels and sometimes directed threats towards them.Increased frequencies of surfacing without blows and dives initiatedwithout raised flukes were some behaviors indicative of avoidance. Greenand Green (1990) reported that humpback whales often reduced the proportionof time at the surface, took longer dives, altered direction as the boatsapproached (horizontal avoidance) and continued to spend more timeunderwater and decreased swim speed (vertical avoidance) after boatsdeparted. These effects persisted over 20 min after the boats departed.Green (199...
