Aug 15 - Cetaceans Of The Strait Of Gibraltar
By Harry Emberley
We who live in the area of the Strait of Gibraltar are privileged. It is a hot spot in both history and biodiversity. It is a place of crossing cultures and migratory routes of humans and animals. Two continents meet from north to south and two seas from east to west. This entails invaluable cultural and biological wealth, which has driven the creation of hundreds of articles describing this diversity. For now we will focus on a single group of animals that, as mariners, makes us happy to observe. We refer to cetaceans; seven are the species that we can see regularly in our environment and are as follows:
Common Dolphin (“Delphinus Delphi”)
It is a very attractive dolphin. The dorsal side is dark grey while the ventral side is lighter. On the flanks two ovals intersect: the front is cream and the back is light grey, forming a characteristic V. The fin is triangular or sickle-shaped. Usually measuring on average about two metres, weighing about 120 kg. Their food, like most dolphins, consists of fish and shellfish.
Common dolphins are resident in the area all year round and can also be seen in the Bay, in my experience, with a certain haunt towards the northwestern sector of it.
Striped Dolphin (“Stenella Coeruleoalba”)
It has a similar size and weight to that of the common dolphin. Although its colour is different, it shares the contrast of dark back and light belly, with a clear bluish grey stripe on its side, from the head to the birth of the dorsal fin. Behind the eye it has three dark lines, one long and two short. The dorsal fin is sickle-shaped.
It is present in our area all year round, sometimes interacting with the common dolphin forming mixed groups. Like the common dolphin, it can be seen in the Bay.
Bottlenose Dolphin (“Tursiops Truncatus”)
It reaches a considerable weight and size, sometimes reaching, and even exceeding, the adult dolphins described previously (potentially doubling them in size and weight). The general colouration is grey, darker on the back and clear belly without drawings on the flanks. It is the typical dolphin found in shows, where they are imprisoned and taught to do the nonsense that us humans so much like.
They live in the Strait all year and, in my personal experience, do not usually come in the Bay, where only rarely I could observe them.
Pilot Whale (“Globicephala Melas”)
The scientific name indicates one of the physical characteristics of this cetacean: black head shaped like a balloon. The overall colour is dark grey with a light spot on the chest. The dorsal fin is sickle-shaped quite long pectorals. Slow moving, can be observed floating in groups on the sea surface. They can reach 5 or 6 metres long and weigh more than 3 tons. They live in the waters of the Strait all year. Personally, I have never seen them in the Bay.
Killer Whale (“Orcinus Orca”)
They are the dolphins of largest size and weight - the adult specimens can reach 10 metres in length and weigh 9 tons. The colour is black with white design on the belly and also white eyespots. After the dorsal fin it displays a grey drawing with the shape of the sign of Aries. The dorsal fins are huge: bigger and sharp in males and smaller and sickle in females. The pectoral fins are rounded.
They can be seen in the Strait during the months of July and August, which come to feed taking advantage of the prenuptial migration of red tuna fish. There are groups that intelligently leverage catches from fishermen and deprive them of the pieces once caught on hooks.
A doctoral thesis has been published recently which shows that these animals are those more likely to survive in their offspring, proposing a plan of subsidies as an incentive to artisanal fishermen to maintain this interaction with killer whales.
Sperm Whale (“Physeter Macrocephalus”)
We can find this animal in the Strait throughout the year. They do not usually enter the Bay although there are some quoted sightings. It is the largest of the toothed whales reaching 50 tons and about 18 metres in length, and usually seeks food consisting of large squids, in the deep sea; it is a great diver and can hold its breath for more than an hour. The colour of its body is dark grey and has a huge head; no dorsal fin having instead a kind of ridges on the tail, ending in a huge caudal fin. The blowhole is at the left of the head, emitting the respiratory jet to that side, which identifies it in the distance although it is not easy to see.
Fin Whale (“Balaenoptera Physalus”)
Although I have seen whales several times, only once I could see the great speed that they are able to exert. In this sighting the ship had to work hard to keep up marking the animal. Some say they are able to cross the Strait in less than an hour. They do not enter the Bay and are only seen in the Strait during their passage, which is not frequent. It's a huge animal, only surpassed in size by the Blue Whale. It reaches 25 metres, weighing up to 80 tons.
The dorsal part of the body is dark grey with white belly and the bottom of the jaw, pectoral fins and caudal fin. The caudal fin is small relative to the body and is shaped like a sickle. The respiratory jet is straight and reaches high altitude. Usually it has a V-shaped mark behind the blowhole and a curious asymmetry consisting of a white right spot of the lower jaw while the left side is dark.
Sailors, when you meet these beautiful creatures, stop the engine or strike the sails. Respect them and observe them. It is worth enjoying and learning from them. It is an absolute joy!
Enrique “Harry” Emberley Moreno is a Teacher, Psychologist, University Specialist in Psychopathology and Health, Doctor in Psychology from the University of Malaga and a Captain with a passion for the sea and the environment.
This feature – ‘Harry’s Cabin’ – is offered in collaboration with Gibraltar Shipping.
Image credit: Isla Kennedy
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