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Type of ships involved

Most of the boats that interact with are sailboats, both monohulls (72%) and catamarans (14%), although there are also interactions with motorboats (6%), semi-rigids (5%) and fishing boats (barely a 3%).

Of all these vessels, the most common type of rudder was the spade one (in 67% of the cases), followed by the semi-supported one (in 22%) and finally the hinged one (barely 1%). In semi-rigid boats and some motor boats, the engine is outboard (approximately 10% of the cases) so the movement of the boat is controlled by the movement of the engine and not by an independent rudder.

The most common rudder among modern commercial sailboats is the spade rudder, present on monohulls (single or double blade) and catamarans (double blade), at the same time it is the weakest since it is normally formed by two joined plates filled with polyurethane on an axis, or wick, that goes in the middle of the plate, still with reinforcements, but without reaching its distal end.​

Table. Relationship between the type of rudder of the vessels with which orcas interact and the type of damage caused, the percentages are calculated based on the total of each type of rudder. Severe damage means being unable to navigate, regardless of the extent of the damage. Rudder: a) spade, b) overshot, c) hinge.


Table. Characteristics of vessels interacted by orcas since 2020, average and range in parentheses of length in meters, and speed in knots.


The average size of the boats involved was 12 meters, although there are differences depending on each type of boat. In the case of sailboats, they are medium-sized boats, and curiously they are not the most registered in Spain, they sailed at a average of 5.7 knots. The boats with which they interacted were both sailed and motorized, and no specific color pattern has been detected that is more or less attractive to orcas, it is not recognized as a reason to reinforce their behaviour, since the entire hull is has interacted with colors.

We highlight the special case of interactions in the Algarve, where the majority were with small semi-rigid boats, which are the most common among whale watching companies in the area. In this case, the interactions consist of physical contact with the floats.​

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Damage and malfunction

As described above, not all boaters who have had an orca sighting or interaction report the situation. While the vast majority are considered to do so, the exact proportion of those who do not report is unknown. Of the total cases registered, and thanks to the effort made to collect this information, it is possible to affirm that 10% of the surfers involved in episodes of interaction provided incomplete information, while in 90% of the cases we have details of the interaction, faults and their magnitude.

In this sense, it is known that in 40% of the cases, the vessels with which they interacted had no consequences, damages or losses. In the same way, it can be affirmed that, among those that presented damage (50% of the cases), 60% were minor damages and, although of a different nature, in no case did they impede navigation. However, the rest of the interactions with damage or breakdown (40%) were considered serious, that is, they prevented navigation and had to be towed. Serious damage included break rudders, which are the most severe cases in terms of damage; axis deviation or internal instrument failures that prevented the normal rotation of the rudder and, therefore, the maneuverability of the boat. 

If we estimate the number of serious damages in relation to the total number of records (sightings and interactions), serious damages, that is, those that prevent navigation, account for only 14% of the total records in the two years, reaching 15% in 2021, a percentage that is increased by a greater number of interactions, but fewer sightings.

Table. Summary of information with/without damage, as well as the type of damage, between 2020 and 2021. Percentages calculated on the respective years.


Table. Summary of orca records, both sightings and interactions with vessels since 2020, with respect to damage.


An external reference of the number of incidents can be the solo Mini transatlantic (, in which at least 90 boats sailed in Galician waters from September 28 to November 4, coinciding with the northward ascent of orcas (Figure 28). Four boats in the race interacted and only one of them sustained significant damage, which would mean 4% of all boats interacted, resulting in serious damage to 25% of the boats that interacted, but only 1% of all boats that participated in the regatta event. However, this is a very imprecise estimate, since there were likely other unreported interactions with other ships and because we do not know the actual number of ships that might have been in the area during those days, which could have exceeded three times the number of boats in the regatta.

In many testimonials, orcas were recorded as pushing the boat, accelerating the speed of the boat, pushing it forward. This pushing took place when the ship was moving or when the ship was stationary, so orcas push the ship regardless of the speed of the ship. This behaviour has no consequences in terms of damage or failure, unless it is carried out under the rudder, after having previously folded the rudder stock (its metal axis) laterally, so that the rudder adopts a horizontal position with a surface suitable for Push.

We check the consequences of the interactions based on the crew behaviour; We analyzed whether or not they followed the security protocol, whether or not they stopped the ship, regardless of whether or not they were aware of or applied the protocol. We consider that the crews did not follow the safety protocol, or did not stop the boat, when they maintained speed, accelerated or reinforced the behaviour of orcas with the aforementioned facts. We believe that the crews followed the security protocol when they stopped the vessel.

Graphic. Consequences of interactions based on the behaviour of ships with

regarding stopping or not stopping the ship.


The results show that there is a slight association between not stopping the vessel (with damage: 51% stop vs. 55% do not stop) and the consequences for the boats, both in terms of damage and serious damage (serious damage: 24% stop vs. 31% do not stop), although the different cases do not show significant differences. That is to say that by stopping the boat, and keeping calm, the boat can be damaged and not damaged, but when the boat is not stopped and/or the behaviour is reinforced, positively with speed, it seems more likely that the boat will end up with damage. and more serious damage. However, in 10 cases, the interacting boats perform both behaviours, for example, they stop at first, but then start the boat, or vice versa, so the effects of this behaviour of the boat (stop/not stop ) can be mixed. These results must be corroborated and reinforced by the studies proposed in the pilot study regarding the behaviour of the ship.

On the other hand, the consequences of the different "techniques" that the boats used to try to deter the orcas during the interactions were analyzed in more detail. These "techniques" can be intentional, such as using bait, flares, diesel, rocks and other objects, backing up, spewing black water, yelling to try to deter the animals; Either the boat simply already had fishing lines in the water, or the music on the boat and its effect on the consequences of interactions have also been considered.

Graphic. Consequences of the interactions depending on the behaviour of the vessels with respect to the use of dissuasive "techniques".​


Alfredo López Fernández and Ruth Esteban Pavo (Coord). 2021. Preparation of a scientific study on the interaction of the Orca (Orcinus orca) population of the Strait of Gibraltar with boats for the design and proposal of prevention, action and management measures. Atlantic Orca-GTOA Working Group/Coordinator for the Study of Marine Mammals-CEMMA and Atlantic Orca-GTOA Working Group. Author names. INTEMARES LIFE project. Biodiversity Foundation.

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