A Spanish Maritime Rescue service boat had to come to the rescue of a sailing vessel on 9 August that had reported an incident with a killer whale 11 miles south of the Spanish coast. This was not the first encounter between vessels and these cetaceans in the Strait of Gibraltar.

Since March, the number of collisions between killer whales and pleasure boats has multiplied, causing up to a hundred damages, according to Spanish public television.

The main target of these cetaceans are sailboats of less than 15 metres in length, which is why the Merchant Navy decided to restrict their navigation on 13 August off the coast of Cadiz, specifically in the area between Cape Trafalgar and Barbate. The fishing boats have not reported any mishaps with the cetaceans so far.

The killer whales mainly interact with the sailing boats, going directly to the rudder and pushing it, they play with the rudder and sometimes end up breaking it. They do this especially when the boats are in motion or moving. If they are going faster, they are even more motivated. These encounters have precedents, but it is the sudden increase and frequency that intrigues the Spanish researchers.

There are records of very occasional interactions in the past, but not in such a continuous way, it is something quite new. This summer and especially in September and October last year they have intensified a lot; but the question is that they hardly ever did so before.

What could account for the increase in incidents?

It may have to do with human management of the bluefin tuna that is their main prey. The fact, perhaps, of having developed strategic stops for tuna catches, for the increase in tuna stocks, may have led to more tuna, and with more tuna there may be more killer whales, and with more young individuals they may be developing a pattern of learning hunting techniques, practising with the sailboats.

The adult individuals tend to remain on the sides of the boat in many of the interactions and it is the juveniles that get under the boat and interact in some cases.

They have no intention of destroying anything at all, they simply develop this behaviour and keep repeating it. It could be some other kind of coincidence. Or it may even be that as the population has grown, they have established this teaching process mechanism for their offspring.

What precautionary measures should be taken?

Although it may seem counter-intuitive, in this case the only thing to do is to stop the boat, turn off the autopilot, take cover in the middle of the boat and do not take your body out of the boat. In a few minutes, they will have moved away.

Why are killer whales important in the marine ecosystem?

They are predators that have a primordial function in the ecosystem; they are at the top of the food chain and it must be taken into account that the food they are going to feed on will be that of the slowest fish, the sick fish.

Therefore, fishermen will catch the most energetic prey, the ones that are in the best circumstances. Those that are weaker will have already been eaten by the killer whale. The killer whale is fundamental to the ecosystem in that it improves the characteristics of its prey.

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