Boat Disturbance

There is a strong concern that the growing interest in watching whales has had negative effects on cetaceans. Both the whale watching industry and the number of recreational boaters interested in whales have increased significantly since the mid-1980s. Increased marine traffic around whales has been particularly dramatic in the trans-boundary region of Haro Strait (near Victoria), where a plethora of recreational boaters, both Canadian and American whale-watching boats, and heavy shipping traffic all converge in critical habitat for endangered southern resident killer whales. At times more than 50 vessels, both commercial and recreational, may follow a single group of 10 to 20 whales (greatest number of boats recorded following a single group of killer whales was 107 in Haro Strait).

Whale watchers not following the Be Whale Wise guidelines. (photo Doug Sandilands)

Kayakers must follow the Be Whale Guidelines too, and always stay on the offshore side of the whales when they are traveling close to shore – unlike this group.

While commercial whale-watching vessel operators are aware of the Be Whale Wise guidelines and generally follow them, many pleasure boat operators are not familiar with the guidelines and frequently interrupt the activities of marine mammals.  Although one boat is not likely to cause significant disturbance just by watching whales, repeated violations of the Be Whale Wise guidelines will lead to significant disturbance of cetaceans.  Kayak and other self-propelled vessels can also disturb animals, especially in heavily-used recreation areas. Data collected by Straitwatch, an on-the-water monitoring group, indicate that southern resident killer whales experience approximately 100 incidents of non-compliance with the guidelines per day from May to September.  Vessel disturbance may lead to:

• Interruption of natural behaviours.  Disturbance by vessels may turn the whales’ attention away from essential activities like foraging, feeding, socializing and breeding.  A study by Rob Williams and colleagues in 2006 investigated the activities of northern resident killer whales in the presence and absence of boats. They found that when vessels were nearby, killer whales reduced their time spent feeding and beach rubbing (an important social activity for this population). The interruption of feeding may also impact the energy intake of these animals and when salmon are scarce, this can be particularly detrimental to their survival. In Glacier Bay Alaska, multi-year studies of humpback whales showed that whales change their behavior in the presence of cruise ships. The typical reactions of whales to the presence of vessels (up to 4 km away) include avoidance by diving underwater or swimming away, reducing surface time, and changing their breathing rates.

• Exposure to high levels of boat exhaust and emissions.  Cara Lachmuth and colleagues’ 2011 study investigated vessel behavior and emission levels in the presence of southern resident killer whales and found that exhaust emissions have the potential to cause adverse health effects. Whales don’t have sinuses to filter air the way terrestrial mammals do and they have no sense of smell to help them detect, and hence possibly avoid, engine exhaust. They also spend much of their time diving, which increases pressure in their lungs and causes air pollutants to enter their blood more rapidly than for non-diving animals. Lachmuth found that current whale- watching guidelines are usually effective in limiting pollutant exposure to levels at or just below those at which measurable adverse health effects would be expected in killer whales. However, safe pollutant levels are exceeded under worst-case conditions and certain average-case conditions. The build-up of air pollutants is mainly due to the formation of a stable atmospheric inversion layer over the ocean which commonly occurs during summer months. This traps air pollutants at the surface where the whales breathe.

• Noise.  Motorized vessels contribute to underwater noise and may reduce the ability of whales to detect their prey, communicate, and navigate.  In 2008, Marla Holt and colleagues found that for every 1dB increase in underwater noise, killer whales will react to noise and try to compensate by increasing their vocalizations by 1dB.  At certain levels, however, communication, and particularly echolocation are completely masked by noise. For harbour porpoises, observed responses to acoustic disturbance range from acute to chronic behavioural changes, such as temporary habitat avoidance to exclusion from regions with chronic increases in noise levels.  See more of the affect of noise on cetaceans here.

Elusive harbour porpoise are particularly sensitive to acoustic distrubance. (photo Alexandra Morton)

The impacts of vessel disturbance occur in conjunction with other threats. This disturbance likely adds to the stresses animals already face like high contaminant loads and decreased food supply. While longer-term studies are required to understand the effect of disturbance on cetaceans in BC, in Shark Bay, Australia, Lusseau and Bejder (2007) have found that the accumulation of short-term responses to disturbance can result in a decline in abundance of bottlenose dolphins. They note that a similar decline could be devastating for small, closed, resident, or endangered cetacean populations.

Vessel Education Programs:

• The Robson Bight (Michael Bigg) Ecological Reserve (RBMBER) was established by BC Parks in 1982 to provide an area free from boat traffic for killer whales that use the area to feed on abundant runs of salmon and rub on the smooth pebble beaches in the reserve (this behaviour is unique to northern resident killer whales). Since 1987, BC Parks has funded the Robson Bight Warden Program which informs boaters in the area of the ecological reserve and the Be Whale Wise Guidelines. Currently the Warden Program is run by Cetus Research & Conservation Society.

Male killer whale beach rubbing. (photo John Ford)

• Straitwatch is a marine mammal monitoring and education program operated by Cetus Research & Conservation Society.  Straitwatch operates in Johnstone Strait and Haro Strait to monitor the activities around local marine mammals, especially killer whales, and provides boaters with information on local marine species and marine mammal viewing guidelines.

• On the American side of the border in Washington State, The Whale Museum on San Juan Island established Soundwatch which also conducts on-the-water vessel education and monitoring.

• Both Straitwatch and the BC Cetacean Sightings Network conduct ‘Dock Talks’ at marinas throughout the Lower Mainland and Vancouver Island, informing boaters of the Be Whale Wise guidelines and other marine mammal information before they leave the dock.


Follow the Be Whale Wise guidelines

Canadian          American          Kayakers

Report violations of the Be Whale Wise Guidelines.

In Canada to Fisheries and Oceans Canada 1-800-465-4336

In the U.S. to NOAA Fisheries, Office of Law Enforcement 1-800-853-1964


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.

Lachmuth, C., Barrett-Lennard, L.G., Steyn, D.Q., Milsom, W.K. 2011. Estimation of southern resident killer whale exposure to exhaust emissions from whalewatching vessels and potential adverse health effects and toxicity thresholds. Marine Pollution Bulletin 62: 792-805.

Holt, M.M, Noren, D.P., Viers, V., Emmons, C.K., Veirs, S. 2009. Speaking up: Killer whales (Orcinus orca)
increase their call amplitude in response to vessel noise. Journal of Acoustic Society of  America. 125 (1):

Williams, R., Lusseau, D., Hammond, P. 2006 Estimating relative energetic costs of human disturbance to killer whales (Orcinus orca). Biological Conservation 133(3): 301-311.

Lusseau, D., Bejder, L. 2007. The long-term consequences of short-term responses to disturbance experiences from whalewatching impact assessment. International Journal of Comparative Psychology 20: 228-236.

Fisheries and Oceans Canada. 2009. Management Plan for the Pacific Harbour Porpoise
(Phocoena phocoena) in Canada. Species at Risk Act Management Plan Series. Fisheries and
Oceans Canada, Ottawa. v + 49 pp.