Abstract:
I studied the effects of vessel activity on the behavior of humpback whales (Megaptera
novaeangliae) near Juneau, Alaska, from 6 July to 25 August 2000. I collected behavioral data from a
7 m inboard-outdrive research vessel in Stephens Passage and Lynn Canal, where feeding Central
North Pacific humpbacks are the focus of a burgeoning whale watching industry. Utilizing
continuous and point behavioral sampling, I recorded locations, identities, and behaviors of 27
humpback whale focal pods for 39.6 observation hours. I also recorded number, type, approach
style, length of stay, and proximity of whale watching boats within 400 m of each focal pod. I
observed 16 pods (1404 total min.; 261 surface intervals) when at least one whale watching boat was
present for more than ten minutes, and observed 11 pods (972 total min.; 191 surface intervals)
when no whale watching boats were present. I compared whale behavior between the two
conditions, whale watching vessels present and whale watching vessels absent. Average whale respiratory activity was almost identical in the two conditions. However, individual whales followed by whale watching boats showed significantly greater variance in time spent at the surface and number of blows per surfacing than did whales not pursued by boats (F=2.87, p<0.05; F=3.14, p<0.05). Additionally, whales with whale watching boats showed significantly greater variance in the proportion of time spent engaging in surface-active behavior (F=284.60, p<<0.001), and collectively exhibited surface behaviors more frequently, than did whales without whale watching boats. Over 80% of whale watchers remained at least 200 yards (182.8 m) from focal whales; however, almost
30% of whale watchers violated NOAA Fisheries' Alaska Marine Mammal Viewing Guidelines by
staying with pods for more than 30 minutes. I found that humpbacks exhibit subtle short-term behavioral responses to whale watching boats, but that long-term consequences of heavy vessel
traffic for this whale population remain to be determined. I provide recommendations to NOAA Fisheries charged with assisting the recovery of the humpback whale and with managing Alaska's whale watchers.
