Princess Alice Bank at the Azores is a volcanic seamount on the Mid-Atlantic Ridge rising from more than thousand metres to a depth of around 40 metres below the ocean surface. The abundance of marine life, especially devil rays (Mobula tarapacana), make it an exquisite, albeit remote and exposed offshore spot for diving.
We wake before sunrise, as the dive boat is set to leave early to motor the 45 nautical miles to the Southwest. The harbour of Horta rests quiet at this hour. We assemble our dive gear and load it into the boat.
Under Way to Princess Alice Bank
We leave the port with a headwind. Light rain drizzles. There’s not much swell, and waves are less than a metre high. Nevertheless our motor catamaran starts to bounce. After an hour, the island of Faial disappears in the clouds. Thick clouds obscure the sky. Another rain squall approaches. The translucent blue sails of Portuguese man o’ war drift in the dark ocean.
Then the sky opens and the sea turns to the deepest ultramarine. After four hours, we have reached our destination at 38°00’20” North, 29°17’54” West: Princess Alice Bank. Nothing but blue water surrounds us.
The Discovery of Princess Alice Bank
The Portuguese are a nation of sailors: Diogo Cão, Bartolomeu Dias, Vasco da Gama, and Fernão de Magalhães (better known as Magellan) are only the most famous of Portuguese seafarers. The epos Os Lusíadas narrates the discovery of the sea route to India by Vasco da Gama, and its author Luís de Camões is celebrated on Portugal’s National Day.
It thus comes as a surprise that Princess Alice Bank was discovered by a foreigner. In 1896, Prince Albert I of Monaco, an avid oceanographer, sailed near the Azores. He discovered a seamount south of Faial Island that steeply rises from more than thousand metres depth. The Arquipélago dos Açores is a volcanic hotspot on the Mid-Atlantic Ridge, similar to other islands such as Iceland, Tristan da Cunha, or Saint Helena. He named the plateau Princess Alice Bank after his research yacht (and second wife Alice Heine, a relative of the writer Heinrich Heine).
Princess Alice Bank became a significant fishing area. Years later, the accounts of ray sightings by the local Azorean fishermen led to its evolution as an offshore dive spot in the midst of the Atlantic Ocean.
Diving with Devil Rays
Our skipper Jairo points to the water: three Manta rays are swimming just below the surface. Princess Alice Bank serves as a pit stop for devil rays who are long distance travellers. The rays apparently like the seamount that steeply rises from over two thousand metres depth almost to the surface. The ascending deep sea ocean current carries food. Moreover, the site seems to be important for social interactions and mating.
Manta rays migrate through the oceans and do so at great depth (>1’800 metres). Devil rays (Mobula tarapacana) are among the deepest-diving ocean animals. The word Manta is Portuguese for cape or mantle. Indeed, their wing-like pectoral fins give the impression of a cape. Also, the name devil ray reflects the appearance of their fins on the head: former scientific names included vampyrus, daemomanta, and diabolichthys. They were seen as diabolic creatures.
We jump into the water. We dive and the tip of the volcanic seamount appears at around forty metres depth. Princess Alice Bank lies 45 nautical miles offshore, that’s 80 kilometres from the nearest Azores island Faial. Pelagic fish surround us: barracuda (Sphyraena viridensis), Almaco jack (Seriola rivoliana), and tuna (Katsuwonus pelamis).
A large group of devil rays appears in the dark blue to our left and glides towards us. The ocean current moves our exhaled air bubbles away. We pay attention not to get carried away, as warned by divemasters and marine biologists Fábio and José. The current can reach several knots and drag someone away several hundred metres in a few minutes.
Fábio dives deeper to free a mobula entangled in a fishing line around the neck. Although the rays move their wings slowly, they are fast swimmers. Fishing is a threat to these ray populations. Their gill plates are sought after for food and Chinese medicine. They are classified as vulnerable on the IUCN Red List of Threatened Species.
To ensure the flow of water through their gills, the rays need to stay in motion. Gliding through the water with open mouths, Mobula eat plancton. Time and again, groups of rays appear in the far blue and quietly pass us. Some of the female animals seem pregnant with protruding bellies. These rays are ovoviviparous, giving birth to freely swimming offspring, not eggs. Their live expectancy is several decades.
José installs an underwater camera that repeatedly takes photos of the site for a research project. It will stay there. The main species found at Princess Alice Bank is Mobula tarapacana. The University of the Azores also has a photo identification study project: the colour shape on the underside of the rays allows their identification for migration studies. However, there are only few, and often remote sites worldwide where these animals can be studied. Indeed, the Azores are among the few places where the rays seasonally aggregate on their migratory routes, in particular at Princess Alice Bank.
We ascend to the surface, trying to avoid the stinging Portuguese man o’ war and climb into the boat, deeply impressed by this place.
Land in Sight
The cliffs at the southern tip of Faial Island appear in the glistening clouds. It’s evening as we approach our homeport Horta. Nowadays, Horta is a popular pitstop for transatlantic sailors. The yachts commonly arrive in May, and leave in September for an Atlantic circuit. A visit to the famous Peter Café Sport for a Gin do Mar is kind of a rite of passage – also for us after these dives.
The Azores archipelago consists of nine islands, however they are small and scattered in the surrounding vast Atlantic. The Azores appeared on sea maps in the 14th century, and were officially taken in Portuguese possession in the 15th century. How many seafarers have sailed by without discovering them? Did the Phoenician or Viking sailors already knew the Azores? Did they marvel at the devil rays as well and were as impressed?