Collisions of ships with both whales and dolphins are increasingly recognised as an international conservation issue. Larger cetaceans such as fin, right and sperm whales, are most commonly affected, or at least more commonly identified as casualties. Collisions can occur with vessels of all sizes, although the more serious incidents tend to be caused by very large vessels, and those going at speeds of 14 knots or more1. Injuries sustained can include fracturing, bruising, nicks or slicing off parts of fins, and the most serious accidents can result in death.
Unfortunately, quantifying the scale of the problem is not an easy task. Whilst evidence of ship strikes comes from direct observations at the time of the accident or subsequent examination of washed up or floating carcasses, many accidents may go unreported. The crew may be unaware of the accident and thus the body could sink and go unnoticed, or they may fail to report it to the appropriate authorities. Getting a handle on the figures and identifying hotspots for collisions, however, is extremely important for implementing preventative measures and for the conservation of these species. Some cetacean populations are particularly vulnerable due to their location within busy shipping areas. Such is the case for the critically endangered North Atlantic right whales off the east coast of Canada and the USA, and of fin whales in the Mediterranean. An investigation into ship strikes by NOAA (National Oceanic and Atmospheric Administration) indicates that at least ten large whale species are affected, with the most frequently reported species being fin whales, humpback whales and North Atlantic right whales2. The most recent incident in Europe, on 22nd September 2009, reported a fin whale being carried into Antwerp, Belgium on the bow bulb of a ship after being killed by a ship strike, most likely outside of Belgian waters.
In areas where large numbers of cetaceans and ships are occupying the same body of water and the risk of collision is potentially high, measures can be taken to minimise the threat. Possibly the easiest measure to implement is to impose a speed limit and in some areas (for example the Strait of Gibraltar), an alternative shipping route has been created to avoid the cetaceans’ main habitat. However, the latter solution is not always practical and sometimes monitoring the interactions between ships and cetaceans and providing information to shipping crew is the best alternative. In the United States, NOAA and the U.S. Coast Guard have implemented Mandatory Ship Reporting Systems whereby ships greater than 300 tonnes entering one of two key North Atlantic right whale habitats must report to a station. The ship then receives information on the locations of recent sightings as well as precautionary measures to avoid hitting whales3.
The Sea Watch Foundation’s Director, Dr Peter Evans, has been commissioned by UNEP (United Nations Environment Programme) and ASCOBANS (Agreement on the Conservation of Small Cetaceans of the Baltic and North Seas) to review ship strike collision risk in the ASCOBANS Agreement Area by mapping areas with greatest shipping movements alongside the distribution of vulnerable species.
Improving awareness within the shipping industry about areas with large populations of cetaceans, providing information about their ecology and ways to avoid collision, and encouraging them to report boat strikes as well as any live animals, could help to reduce such incidents, and provide further information on areas where more drastic measures need to be taken to ensure low mortality rates from such causes.
1 Laist, D.W., Knowlton, A.R., Mead, J.G., Collet, A.S. and Podesta, M. 2001. Collisions between ships and great whales. Marine Mammal Science 17(1):35-75.
2 Jensen A.S. & Silber G.K. (2004) Large whale ship strike database. NOAA Technical Memorandum NMFS-OPR-25.
3 Silber G.K., Ward L.I., Clarke R., Schumacher K.L. & Smith A.J. (2002) Ship traffic patterns in right whale critical habitat: Year one of the mandatory ship reporting system. NOAA Technical Memorandum NMFS-OPR-20.