Collisions Between Vessels and Whales
Cetacean species are very susceptible to serious injury and mortality from vessels. Areas of high marine traffic can pose a lethal threat to these animals, especially in “bottlenecks” where both whale and ship densities are concentrated (Williams and O’Hara, 2010). Unfortunately many incidents of ship strike around the coast go unnoticed or unreported, and this makes it difficult to understand the scope of the problem. For instance, large vessels such as cruise ships may not perceive the impact of a collision – even with a large whale species. In fact in 1999 and again 2009, a fin whale was struck by a cruise ship in BC waters. Jensen and Silber (2003) reported that fin whales are the most frequently struck large cetacean, at nearly twice that of the next most commonly struck species – humpback whales. Injury and death as a result of ship strikes are significant threats to recovering populations of marine mammals and also has the potential to damage smaller vessels and cause injury to passengers.
However, big ships are not the only boats responsible for cetacean collisions. The summer of 2006 was an unfortunate season in BC as two killer whales, two humpback whales and a minke whale were seen either being struck by vessels or were observed with recent scars from collisions with vessels. Both killer whales involved did not survive and one of the humpback whales has not been resighted since.
In Glacier Bay, along Alaska’s Pan Handle, an unusually high number of humpback whales were found dead in 2010. The necropsies of two whales in particular found injuries consistent with high impact blunt force trauma, such as skull fractures. In both cases vessel collision was determined as the cause of death (Neilson and Gabriele, 2010).
Fin whales, humpback whales, and killer whales may be the most common whales involved in vessel collisions, but researchers are starting to notice evidence of ship strike among smaller cetaceans as well. In April 2011, Pacific white-sided dolphins were foraging in Howe Sound and several animals displayed the tell-tale scars and injuries inflicted from a boat. One animal was observed with a severed dorsal fin and other dolphins were photographed with propeller scars on their backs.
WHAT YOU CAN DO
1. Observe the Be Whale Wise Guidelines
2. Slow down to less than 7 knots within 400 m of whales.
3. In areas of known cetacean activity, reduce speed and keep a lookout for signs of whales, dolphins and porpoise. Remember- whales don’t always know where you are!
Neilson, J. L. and C. M. Gabriele. 2010. Results of humpback whale population monitoring in Glacier Bay and adjacent waters: 2010. Report to the National Park Service, Glacier Bay National Park and Preserve, Gustavus, AK. 20 pp.
Williama, R. and O’Hara, P. 2010. Modelling ship strike risk to fin, humpback and killer whales in British Columbia, Canada. Journal of Cetacean Research and Management. 11(1): 1-8.
Jensen, A.S. and G.K. Silber. 2003. Large Whale Ship Strike Database. U.S. Department of Commerce, NOAA Technical Memorandum. NMFS-OPR- , 37 pp.