One of the reasons why we can enjoy beautiful sightings with cetaceans around Madeira is because the deep waters surrounding the island house a variety of their desired prey. Cold water currents carrying nutrients gush through the steep, submarine terrain surrounding the archipelago and create the foundation for an incredible diversity of life, both in the abyss and at the surface.
Both our boats had the pleasure of having some close encounters with different species of cetaceans today, who all vary in their preferred prey and site fidelity to Madeira. While our Ribeira Brava drove to the waters further east to meet our frequent visitors, the Bottlenose dolphins (Tursiops truncatus) and the Short-finned pilot whales (Globicephala macrorhynchus), our zodiac sped for the waters in the far west this afternoon to see our summer dolphins, the Atlantic spotted dolphins (Stenella frontalis).
Short-finned pilot whales mainly hunt in the deep where they usually target deep-sea squid, a very hydrating and abundant prey around the island. Squid are also an important prey for spotted and Bottlenose dolphins, with the latter often even joining forces with the pilot whales to gain feeding advantages. Most oceanic dolphins also feed on a variety of smaller schooling fish such as Atlantic mackerel (Scomber scombrus), Longspine snipefish (Macroramphosus scolopax) and Atlantic Horse mackerel (Trachurus trachurus). Bottlenose dolphins also target larger fish such as Dolphinfish (Coryphaena hippurus) or Skipjack tuna (Katsuwonus pelamis).
The variety of deep-sea fish, particularly those that often migrate up to shallower areas of the water column like the Silvery John Dory (Zeus fabre), can also provide an opportunity for a good meal. John Dorys are demersal coastal marine fish that occur near the seabed between depths of 5 to 300m and are easily recognised by the large, dark eye spot on their flanks and their long dorsal spines. The eye-spot reminds of the “evil eye” fisherman folklore of the Mediterranean, that is used to fight off evil spirits and bad luck at sea. In the case of the fish, the eye spot’s function is to scare off predators or confuse prey but this doesn’t always work out as planned for the fish. Mediterranean monk seals (Monachus monachus) are voracious predators in the archipelagos waters and often hunt this species, which was probably the reason why the John Dory we found drifting dead at the surface this afternoon had such a big bite mark on its tail. The dead fish was however, together with the lovely sightings of dolphins, once again proof of the incredible diversity found in Madeira’s waters.
By Paula Thake
Sightings of the day
10:00 Bottlenose dolphins, Short-finned pilot whales
15:00 Atlantic spotted dolphins