The Orcinus Orca or “Killer Whale” got this nickname because they are known to eat other marine mammals such as seals, dolphins, or young whales. No humans have ever been killed by Orcas in freedom, and the only known cases of humans being killed by killer whales were by animals in captivity. I invite you to read an article I wrote called “marine mammals in captivity” to be found on my LinkedIn, Facebook, or look it up in “The Islander” magazines’ digital format (May 2020).
Before entering in detail about the Orcas and their interaction with humans we first need to understand the fishing of the largest tuna in the world, which is as main reason behind the reason of the Orcas visiting the Strait of Gibraltar. The Atlantic Blue-fin Tuna (Thunnus thynnus), or in Spanish “Atun Rojo”, is the largest tuna in the world. This fish can weight up to 680 kg and generally swims between 500 and 1000 meters deep. This apex predator lives generally till the age of 15 to 30 years. This pelagic specie does not use their gills for oxygenation like other fish, as they keep their jaw open for which they need to swim in order not to suffocate. This is the main reason why these tunas cannot be bread in “normal” fish-farms, unless you tow the whole of the fish-farm out through the open water with boats. These tunas will migrate from the Atlantic Ocean to the Mediterranean Sea for their spawning activities (fertilisation and releasing of eggs) in order to guarantee their progeniture. 30% of this migration includes tuna that have travelled from the Gulf of Mexico and therefore cross the Atlantic Ocean twice a year. The spawning will happen somewhere between May and August, with its peak between June and July. One of the main spawning areas includes the South of the Balearics islands, which happens around 2-4h.am at a depth of 4 to 5 meters. Important fact to remember is that a tuna of 15 to 20 years old will lay about 45.000.000 eggs, from which only a small percentage will make it to adult age.
Orcas swim max. 50-55 km/h, where these tunas can swim about 70-100km/h. and it is therefore quite difficult for the Orca to catch a Bluefin tuna. We, humans, are of course interested in catching these tunas as well, and we do that since a long time. Proves of tuna fishing in this particular area of the world can be found in the Roman ruins of Baelo Claudia, two centuries B.C. The presence of Orcas also goes back to the time of the Roman, which can be found through the indication of the name “Cabo Espartel” on the maritime chart of this area (on the Moroccan coast). The name “Esparte” is, still today, how Moroccan fishermen call the Orca referring to the dorsal fin (esparte = spade), which for a male 9 meters/ 9 tons individual can be as high as 2 meters.
We need to differentiate two types of tuna fishing arts in this area of the world.
1. Almadrabas, which is a specific type of purse seine fishing, catching tuna before entering the Mediterranean and therefore before the spawning activity takes place.
2. Palangre: a type of long-line fishing, which takes place after the spawning when the tuna swims back to the Atlantic Ocean.
ALMADRABA: Four Almadrabas are laid out from the little fishing villages of Conil, Barbate, Zahara de los Atunes and Tarifa, on the Spanish Atlantic coast just before the entrance to the Mediterranean. You can picture the Almadraba by imagining an underwater fence of over a kilometre long which guides these large tunas swimming along the coast into a labyrinth of nets which ends in a central cage called “El Copo”. Once enough the tunas are caught, fishermen will lift this cage to the surface through block, pulleys, and lines with the help of small boats equipped with pillars. Once the nets are lifted, men will step in there till their chest in the water, equipped with large hooks to drag the tuna alongside their boats to get hoisted. The scenery is bloody and extremely dangerous for the men itself as the fins of tuna are sharp as razorblades. The tunas are caught before they had the opportunity for spawning, with the obvious repercussion and additional pressure on the dramatic drop in population this specie.
PALANGRE: Once the tuna schools head back out of the Mediterranean, they will be hungry as they have not been eating for a little while. The Spanish and Moroccan fishermen know that and will be waiting for them in the middle of the Strait to catch them. The deepest point in the Strait of Gibraltar is about 1000 meters deep, but in some areas, it is only about 300-400 meters deep. The palagre fishermen prepared their long lines, equipped with hooks, using sardines as lures in the harbour. Once at sea, these lines are dropped down to the bottom by throwing the hook attached to a cement block overboard. Once the hook reaches the required depth, they give the line a strong pull to break a thin line between the hook and the stone. The tunas swimming up these underwater hills will encounter the sardines as a well-deserved bite… and the fight is on! You would be surprised to see how, especially the Moroccan fisherman, handle the lifting of a 200-300 kg tuna bare-handed from their little 8-9 meter wooden boat. The Spanish fishing boats are not much bigger but might be equipped with a hydraulic winch to hoist the tunas on board. That is the moment of opportunity the Orcas have been waiting for. When the fishermen have the tuna about 30-40 meters under their boat, the killer whales will steal the tuna from the fisherman. They will bite the belly of the tuna first (la ventresca), which is the fattest part of the tuna. The Orcas have been seen changing their course sometimes as a reaction to the noise of the hydraulic winches being activated. They know exactly when to attack and after the first bite in the belly they will try to steel the whole tuna off the hook of the fishermen. The presence of youngsters within the pods indicate that the opportunity to teach their calves in the process is used. The head of the tuna, where the hook is located, is never part of the attack. They might remember that they should stay away from the head/hook or might use their echolocation to sense the hook. It has always surprised me to see the how acceptant these fishermen are toward the Orcas … I mean, surely there is not a lot they can do to a pod of Orcas from their small boats, but still… Also, over the years, the fishermen got used to the presence of the whale-watch boats and sometimes show-off with the leftovers of the tuna after the attack for the tourist to make pictures.
A total of about 45 Orcas have been monitored in this area which is divided into 5 pods (=families). Two pods will not interact with humans and have only been seen approaching the bay of Cadiz or Barbate. One pod will get closer to the palangre fishermen but will not interact, as maybe they do not know how to do the stealing or might be scared of the interaction. And the remaining two pods are the ones engaging in the interaction of trying to rob the tunas of the fishermen.