Impacts of Whale-Watching on Blue Whales (Balaenoptera musculus) off Southern Sri Lanka

Abstract

Blue whales inhabit the coastal waters off southern Sri Lanka throughout the year, due to a narrow continental shelf and upwelling, related feeding opportunities. A busy, international shipping lane also lies off the south coast. While blue whales are listed on the IUCN Red List of Threatened Species, the subspecies status and genetic affinities of this northern Indian Ocean population is not well understood. Since 2009 a rapidly expanding, boat-based, commercial whale-watching industry has developed off the south coast, but remains unregulated due to the non-existence of national regulations or codes of conduct. As a result, unethical practices are leading to harassment of the targeted whales. Comparison of sightings data from before and after whale-watching began, shows a shift in the area of occurrence and concentration of whales. Simultaneously there is an increase in the number of stranding and vessel collision related mortality. These factors indicate that current whalewatching practices are displacing whales from their preferred feeding areas and inadvertently pushing them offshore into the shipping lane, causing an increase in fatal vessel collisions. It is recommended that a precautionary principal is followed and whale-watching activities are regulated as a priority, in order to mitigate any adverse impacts.