21st Century ShippingAvoiding a collision course to save whales
Research into blue whale distribution around one of the world’s busiest shipping lanes and fatal collisions with ships has led scientists to offer a simple solution to the deadly threat.
Heavy ship traffic crossing the Indian Ocean passes close to the southern coast of Sri Lanka, bringing it into waters also occupied by the endangered blue whale, the largest animal on the planet.
Survey work coordinated by the University of Ruhuna in Sri Lanka, local whale watch operator Raja and the Whales, International Fund for Animal Welfare (IFAW), Biosphere Foundation and Wildlife Trust of India (WTI) in 2014 and 2015, was carried out with the aim of finding ways to address blue whale deaths in the ship strike hotspot off the coast of Mirissa.
A paper on the findings, ‘Distribution patterns of blue whale (Balaenoptera musculus) and shipping off southern Sri Lanka’ was recently accepted for publication in Regional Studies in Marine Science.
Eleven blue whales were known to have been killed by ships between January 2010 and April 2012 but the true number of ship strike-related deaths is likely to be much higher as for part of the year the current and winds are offshore, meaning additional whales could have been killed but their carcasses not found.
Data from the study suggests the risk to blue whales could be reduced by 95% if the shipping lane is moved slightly so that traffic passes 15 nautical miles further south than at present.
Patrick Ramage, IFAW’s Global Whale Programme Director, said: “It is not often that a serious threat to whales can be so easily resolved and at minimal cost, but here we clearly see not only the problem, but also a straightforward practical solution which can prevent more endangered blue whales from suffering fatal ship strikes.
“A little more analysis is needed before Sri Lanka can start the process of asking for the shipping lane to be moved, but we are confident that this step will result in a dramatic reduction in the number of fatal collisions involving this great whale.”
The population of blue whales in the northern Indian Ocean is believed to be very small.
Vivek Menon, Executive Director of WTI, added: “Moving the shipping lane this short distance would provide a positive solution for all. It would increase protection for whales and whale watching boats in the area and therefore also help tourism.”
Surveys conducted perpendicular to the shipping lane were used to determine the relative density of whales close to the shore, both in the existing shipping lane and further offshore. The highest density of blue whales was observed in the shipping lanes.
Previous data on blue whale distribution and coastal upwellings (a process by which deep, cold water usually rich in nutrients rises towards the surface) indicates consistent and predictable patterns of whale distribution. This provides considerable potential for effective measures to keep ships and whales apart.
High densities of whales combined with one of the busiest shipping routes in the world suggest a severe risk of ship strikes.
Researchers estimated that more than 1,000 interactions between blue whales and ships were likely to occur each year. An interaction is defined as an incident where a collision would have occurred if neither ship nor whale had taken avoiding action. Moving the shipping lanes could reduce this to around 50, a reduction of 95%.
In order for the shipping lane to be moved, Sri Lanka would need to bring forward a proposal for consideration by the International Maritime Organization. Additional data continues to be gathered and further analyses will be coordinated through the Scientific Committee of the International Whaling Commission.
Shipping lanes in other parts of the world have been successfully moved in similar circumstances. In 2007, a shipping lane in the approaches to Boston Harbour, US, was moved in order to lower the risk of collision with right whales by avoiding the main area of density, cutting the risk of collision by an estimated 58%.
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