14.02.2006

Orcas in der Straße von Gibraltar

FIRMM (Foundation for Information and Research on Marine Mammals) is one of the four companies in Tarifa that organize excursions to watch cetaceans. The most interesting excursions look for Orcas.

Orcas (Order:Cetacea, Suborder:Odontoceti, Family:Delphinidae) have always been in the Straits during the migration period of Red Tuna (the favourite food of these fascinating animals).  Cape Espartel in Morocco is named after the Arabic word for Orca (Esaprte). In front of Cabo Espartel the water is 50 metres deep in places and used by Orcas to hunt Tuna, which are unable to dive and escape. To understand the presence of Orcas, we must learn about the migration of Tuna. Orcas have been known since the time of the Phoenicians. They helped these Mediterranean sailors identify the presence of Tuna, which can weigh nearly half a ton.

In the spring, Tuna enter the Mediterranean to spawn around the Balearic Islands, Sardinia and Sicily. Many years ago Tuna were so abundant that they even spawned in the Black Sea, but over-fishing has also affected the number of this species. In spring, ‘Almadrabas’ (special nets) are positioned at different points along the Andalusian coast to catch Tuna before they enter the Mediterranean.

In the summer, the Tuna return to the Atlantic where those that survived the long journey, and managed to escape the Almadrabas, are awaited by more fishermen. This time they use lines with hooks. Sometimes a fisherman has to fight for two hours to catch a Tuna.

Tuna swim quickly and are therefore difficult prey for Orcas, which only have a maximum speed of 45km/h. Using intelligence and teamwork Orcas can solve this problem. They have devised numerous hunting techniques all over the world that vary according to the place and the prey being hunted.  Contrary to popular belief, not all Orcas attack other marine mammals. It is this bad reputation that has given the name ‘Killer Whale’.  In The Straights they only eat fish and have not been seen attacking other cetaceans present in the sea around Tarifa.  The current group consists of 15 individuals; 1 mature male (Camacho), various females and some youngsters. A young male has been missing since 2004.

In the spring, Orcas can be seen around the almadrabas, using them to hunt Tuna, therefore making them easier prey. The fisherman also benefit because during this process most of the Tuna are diverted towards the net cage which is the final part of the labyrinth of the almadraba. This shows that we shouldn’t always see cetaceans as competitors for ‘our’ food.

During July, August and September, Orcas can be seen prowling between the fishing boats waiting for the Tuna that are returning to the Mediterranean to spawn. The 3-hour excursions, organized by FIRMM, watch the Orcas here. It is fascinating to see how they have learned that the hooked Tuna gives them the easiest prey that they could hope for. The Orcas never eat the head because they can locate the hook using their sonar system, which all cetaceans have.

In spite of there being an obvious conflict of interests between humans and Orcas, we should never forget that the scarcity of Tuna is not the fault of the Orcas. In fact there is a potential for collaboration between the fisherman and the Orcas, as the Almadraba shows.
P.S This summer the Orcas have hardly been seen near the fishing boats because they have had little success fishing the few tuna that remain.