Whale Watch Out (ship strikes on whales)

Humans have always had an impact on whales.  From prehistoric times, whaling was a key feature of many human communities.  Meat, skin, and organs provided food.  Bones became tools, and baleen a strong fibrous material for fishing lines, roofs, and baskets.  With the industrialization of an unregulated commercial whaling industry, whale numbers plummeted across the globe.  On 2nd December 1942 the International Convention for the Regulation of Whaling which was signed.  The International Whaling Commission (IWC) was established to ensure “the proper conservation of whale stocks and thus make possible the orderly development of the whaling industry”.  Today, whaling has largely declined, undertaken by just a handful of countries and whale-dependent communities.  Never-the-less the human impact on this enigmatic group has not ceased.  Like many marine species, whales can be impacted through overfishing their prey, ocean warming and acidification, noise pollution, toxins in the water, and loss of essential habitat.  Perhaps most noticeable to the public is when whales come into contact with vessels, seemingly often with fatal results.  

A number of cases of whale strikes have made the news.  In September 2010 a blue whale was found on a cargo ship bow in the Port of Oakland.  April 2014, a fifty-five foot fin whale was found on a container ship bow in New York Harbour.  It’s not just commercial shipping that poses a strike risk to whales.  Going through historical reported strikes on humpback whales in Hawaiian waters, researcher Dr Marc Lammers from the Hawaii Institute of Marine Biology discovered that 61% of the strikes involved tour boats – whale watchers, snorkelers, and divers.  This only reflects reported strikes, with "The lack of incidents reported involving large ships [being] somewhat curious". 

Not everyone reports strikes, even when they are supposed to do so.  With the data we do have, the impact of strikes on some whale populations appears somewhat minimal.  The endangered North Pacific humpback population, Dr Lammers notes, is currently experiencing an estimated 6% annual increase in population size.  More recently, University of Washington Doctoral student Cole Monnahan noted that the endangered eastern North Pacific blue whale population has also experienced an increase, with ship strikes having little impact on their recovery.  More so, Cole and colleagues estimate that an 11-fold increase in strikes would result in a 50% change that the long-term population would drop below ‘depleted’ levels.  

Not all whale populations have experienced recovery though.  Despite commercial whaling of the Antarctic blue whale ceasing in 1972, analysis lead by aquatic and fisheries scientist Dr Trevor Branch of the University of Washington estimated that the population continues to remain just under 1% of its pre-hunted abundance.  For such populations, strikes may impede population recovery.

Regardless of population status, strikes are undesirable.  “Nobody wants to hit a whale” states John Berge, Vice President of the Pacific Merchant Shipping Association, "for the same reasons that nobody driving down the highway wants to hit a deer, or a possum, or a skunk”....

The full article was published and can be read in The Marine Professional – a publication of the Institute of Marine Engineering, Science & Technology (IMarEST)

Image: By Pier Nirandara/Flickr (CC BY-NC-ND 2.0)