Activity Patterns and Speeds of Large Cruise Ships in Southeast Alaska

Abstract

We characterized activity patterns of large cruise ships in Southeast Alaska, where there is considerable overlap with aggregations of endangered humpback whales and where lethal ship–whale collisions have been reported. Using Automatic Identification System (AIS) data from 451 voyages representing 26 cruise ships ( = 270 m), we summarized traffic intensity, speed, and timing (day vs. night) for the 2012 summer cruise season in Southeast Alaska. Traffic intensity was found to exceed 700 transits in some areas, which constituted up to 10 ships transiting these areas per day during peak season. Throughout most of the study area (68% of 5 × 5 km cells) average ship speed was >16 knots, and often >18 knots. About half (47%) of the time spent cruising occurred at night when detection and avoidance of whales by ships is likely low. Although whales in Southeast Alaska were subject to low levels of shipping traffic relative to other major shipping routes, cruise ships transited throughout the majority of our study area at speeds where the probability for lethality, should a collision occur, is high, potentially offsetting the relatively low traffic levels. Our results help identify areas of greatest relative risk to whales and locations where whale conservation measures may be most effective.

Keywords:

• cruise ship traffic
• humpback whale
• ship speed
• ship–whale collisions