Leviathan and the Behemoth

From Marina Smir we sailed north to Spanish-owned Ceuta on the northern tip of Morocco. We only had one evening but in between shopping and preparing for an early morning start, we had time to explore the immense fort built by the Spanish to keep the Moroccans out a couple of hundred years ago. With Lily and Katie still asleep, we got underway at 7am the next morning, slipping from the marina under cover of darkness, out through the outer harbour, to cross the Straits of Gibraltar, geographically, economically and ecologically one of the world’s most interesting stretches of water.

DSCI0279The Mediterranean is home to at least seven cetacean species. The greatest profusion of whales and dolphins is in the western Mediterranean, close to and in the Strait of Gibraltar. Bottlenose, common and striped dolphins and pilot, sperm, orca and fin whales all thrive here thanks to a unique set of oceanographic, geological and ecological circumstances. Here, the salty and diminishing Mediterranean Sea is replenished by the less salty Atlantic and this meeting of waters and the currents produced give rise to a rich ecosystem.

At least 30 known individual orcas live here year-round, feeding on the huge red tuna that also support the vibrant fishing economy on the Atlantic side of the Strait. There are also estimated to be 3000 fin whales here, the second largest of the whale species.

But the whales and dolphins are not alone. Here’s some data about what they share their home with:

– The Mediterranean is 0.8% of the global ocean surface, but it has 30% of the world’s shipping traffic.
– At any moment there are approximately 2000 merchant vessels greater than 100 tons in the Mediterranean.
– 200,000 of these behemoths cross the Mediterranean each year.

And in the western Mediterranean, the very conditions that make the region so attractive to whales and dolphins and the entire ecosystem that supports them, give rise to the greatest concentration of merchant vessels.

DSCI0311The Strait of Gibraltar is 14km (7.7 nautical miles) wide and in 2003 (the most recent data I could find), 61,000 merchant vessels of more than 100 tons transited the Strait. That’s 167 ships every day, or 7 ships every hour of every day. There are also regular ferries between Ceuta and Algeciras on the Mediterranean side and Tangier and Tarifa on the Atlantic side.

Crossing the Strait is like crossing a busy street. The Traffic Separation Scheme keeps east-bound vessels to a two-mile southern corridor and west-bound vessels to a two-mile northern corridor, with a half-mile separator zone in between.

The mind-boggling scale of the shipping through the Strait of Gibraltar is fuelled, in part, by our insatiable desire in Europe for outsourced consumables produced in China, India, Indonesia and elsewhere. The large box-like container vessels, carrying all that stuff we’re so addicted to buying, make their way through the Suez Canal, across the Mediterranean and out to the Strait, before turning north to the ports of northern Europe. Julian and I imagined the objects aboard these massive vessels – everything from clothes to computers, batteries to bicycles, Happy Meal toys to sex toys.

Who’d want to be a leviathan amidst these behemoths? 26% of dead whales found stranded on Mediterranean beaches show evidence of having been struck by vessels. And many dead whales never reach shore. The large and relatively slow-moving fin whales are particularly vulnerable as they are unable to turn quickly enough to avoid collision with fast-moving ships. A soft-fleshed living creature is always going to fare second best in a collision with a 100-ton hunk of metal.

Cetaceans, of course, communicate using highly sophisticated calls and songs, cheeps and squeaks. Their communication is drowned out by the immense water-amplified noise of all those ship engines. How do whales and dolphins continue to communicate in such conditions? There is scientific evidence that cetacean strandings sometimes result from confusion due to noise pollution, and there is other scientific evidence that some species have significantly altered the frequency of their vocalisations in order to be heard through the noise.

Spanish and Moroccan governments have taken steps to manage shipping through the Strait to minimise the impact on cetaceans. Starting in 2007, from April to August each year, when the whale population is at its greatest due to migrating species, there is a 13-knot speed limit in the Traffic Separation Scheme, in order to reduce the likelihood of fatal collisions.

Julian and I had forgotten about the seasonal speed limit (it doesn’t affect us, as Carina rarely makes more than 7.5 knots), and at first were confused by the slow progress of the vessels we encountered on the crossing. Were individual vessels going in front or behind us? Did we need to alter course? Once we remembered the speed limit, the crossing became easier and slightly less fraught with trepidation.

Despite the great populations of whales in the Strait, we sadly didn’t see even one. But two days later, as we sailed northwest from Barbate towards the Spanish-Portuguese border, I caught a glimpse of the unmistakable sleek black dorsal fin of a female orca. She was swimming towards the tuna nets, following a meal of red tuna. She appeared once again, a little farther astern and I was ecstatic to have my first ever, albeit brief, sighting of an orca. I hoped she would fare alright if her journey took her to the Strait of Gibraltar.

(Some of the information in this post comes from Vaes and Druon‘s 2013 report published by the European Commission)

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2 thoughts on “Leviathan and the Behemoth

  1. Thanks for educating us! Wow, interesting stuff – I’m amazed at all that marine traffic, ignorant as I am – Gord is less amazed, he has a good memory and a good grasp of all sorts of worldly matters 🙂

  2. Pingback: Green living | Carina Of Devon

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