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”.

All types and sizes of vessels are involved with strikes, ranging from large cargo vessels down to jet-skis, but as ecologist Dr David Laist from the Marine Mammal Commission demonstrated, size does matter.  Investigation of 23 fatal whale strikes revealed that 87% of the strikes involved vessels over 80 meters long.  The impact of strikes for the individual whale being struck isn’t just confined to fatality.  Some strikes may cause internal damage, like hemorrhaging or broken bones, or external injuries like propeller cuts, which may or may not eventually result in mortality.  Fatal strikes to females which have a dependent calf will result in the loss of the calf. 

Determining the frequency and extent of injuries and fatalities is difficult, in part because strikes - especially by large cargo vessels, may go unnoticed.  For the endangered North Atlantic right whale, Dr Scott Krauss, Vice President for Research at the New England Aquarium’s Edgerton Research Laboratory estimated that just 17% of North Atlantic right whale strikes are detected.  Whales that suffer delayed mortality due to strikes are even less likely to be detected, partly because the carcasses tend to sink.  Even when carcasses do wash ashore, ascertaining precise cause of death can be difficult.

Whale strikes can also be dangerous for mariners in small to medium sized vessels.  In 1991 a US Navy hydrofoil struck a whale, warping the hull and breaking the steering arms on both sides of the vessel.  In 2009 experienced sailors Paul and Helen Glavin’s yacht, the Mary Gee, struck a whale near the British Virgin Islands.  Resulting in a serious hull breach, the couple was forced to abandon the stricken vessel.  They were fortunate to be picked up by another yacht in the area.

With boat traffic both increasing and expanding into previously little used areas like the Arctic, and some whale populations showing signs of recovery, our interactions with whales is likely to increase.  To reduce the risk of strikes, there are a number of measures currently being implemented.  The use of observers or technologies such as passive-acoustic monitors and forward-looking sonar to detect and thus avoid whales is a step in the right direction.  But detection can still be difficult, and avoidance not always possible.  Reducing speed through areas known to be used by whales is becoming a popular choice, and not just because it increases the likelihood of detecting a whale. NOAA Research Wildlife Biologist Dr Richard Pace and Fishery Biologist Dr Gregory Sibler’s work on North Atlantic right whale impact estimated that the probability of mortality or serious injury increases from 45% when a vessel travels at 10 knots, to 75% at 14 knots, and at 17 knots the probability increases to 90%.

Off the US East Coast, NOAA implemented seasonal management areas with associated speed reductions appear to have had some effect, with no reported right whale mortalities since its implementation in 2008.   Taking a more dynamic approach, the use of at-sea observers as well as stakeholder driven data collection, can provide near real-time observation reports, allowing managers to implement real-time speed restrictions based on where whale activity is actually occurring.  The Stellwagen Bank National Marine Sanctuary’s WhaleALERT application both collects data and allows regulators to disseminate information to mariners whilst at sea.  

Arguably the best way to avoid strikes is to not be in the same place at the same time as whales.  In 2002, shipping lanes in the Bay of Fundy were moved out of a key North Atlantic right whale feeding ground with, an estimated 62.  In a similar vein, Dr Ladd Irvine of the Oregon State University Marine Mammal Institute has suggested that moving the busy shipping lanes off the Californian coast during blue whale migrations may reduce the likelihood of impact.  Working with the Pacific Merchant Shipping Association, regulators are already altering some shipping lanes to avoid areas known to have high densities of whales.  Rerouting vessels to avoid whales does have its difficulties.  First our knowledge of the spatio-temporal distribution of many whale populations is incomplete.  Whilst at-sea observers can provide near real-time information on distributions, it is unlikely to be feasible to change shipping routes – especially around busy ports – in a sufficient time scale to create the desired avoidance.  Rerouting vessels requires improving our predictive whale distribution modelling.  On the socio-economic side, there may be cost implications to mariners and commercial businesses, such as through increased fuel usage, or travel time.  Sure nobody wants to hit a whale, but equally the costs of avoiding doing so need to be realistic. 

No one tool is the answer to the whale strike problem, with a mixture of these different tools necessary for effective mitigation.  Equally important is the collaborative effort of scientists, regulators, and mariners of all types to improve our understanding of and live alongside these enigmatic creatures.

The article was written for The Marine Professional – a publication of the Institute of Marine Engineering, Science & Technology (IMarEST).