BBC documentary of killer whales off the coast of Cadiz attracted by huge tuna captured by the almadraba fishing technique.
From The Natural World – Wild In Spain. Unfortunately it features Micheal Portillo.
The almadraba is an elaborate and age-old Andalusian technique of setting nets in a maze that leads to a central pool called “copo”. The maze uses just two net lines, called “raveras”. One net is connected to the shore and other line is secured in deeper water. Those lines have smaller oblique lines which leads to the central pool. Tunas are not able to see the exit from the central pool and remain inside. This simple maze works because tuna tend to go into the Mediterranean during spring and the beginning of summer. The floor of the central pool is raised in order to catch the tunas and when that floor is up, there is little room for tunas and they are then caught easily and slaughtered. Wikipedia
From Dolphins and whales in the Strait of Gibraltar
Killer whales (Orcinus orca) visit the Strait of Gibraltar during the tuna migration season in July and August. At the same time Spanish and Moroccan fishermen fish for yellowfin tuna, using longline fishing technics, they lower their fishing lines, armed with several hooks, vertically to the sea bottom. This fishing procedure is possible only in a limited area, where the depth of sea is only 100 metres. Killer whales, being intelligent animals, found out that it is much easier to take a tuna already caught on a fisherman’s hook, than to race with a fish in all its strength. Fishermen must often be satisfied with no more than the head of a tuna; orcas never eat the head of the fish as it contains a metal hook. This is the most dolphin safe of all methods of tuna fishery.
The killer whale population of the Strait of Gibraltar is only 12 animals (2006). There is a photo-identification catalogue of them. They are rather difficult to observe: they can only be found easily if tuna fishermen are on the sea, and the orcas hang around them. In any other instances, whale-watchers only can come across them by chance.