Just like the day before, early in the morning, starting the day, we came across a group of 9 common dolphins (Delphinus delphis). As they did not approach the ship, we continued our course toward the Castro Verde seamount.
We made the first immersion with the Rov in the canyon near the seamount on a muddy-detrital bottom. We found small sharks (Galeus melastomus, Scilirhinus canicula), octopi (Eledone cirrhosa), common whelks (Buccinum undatum), European congers (Conger conger) and some small corals. However, we did not find a great diversity of species or a particular abundance of organisms so we made a second immersion at Castro Verde seamount some 10 nautical miles offshore.
We had already been discussing documenting the bottom of this seamount with great interest. This is because it consists of a traditional Cantabrian coastal fishing area. During the evenings that we docked in Castro Urdiales, numerous inhabitants of this village let us know about the area's interest as well as the importance of documenting its bottoms and learning what is really out there today. Unfortunately, we found a bottom that had clearly been exploited a great deal with numerous remains of nets and fishing lines where we were once again surprised by the scarcity of fish that remain at the seamount. Besides some sponges such as Phakellia ventilabrum, corals such as Dendrophyllia cornigera, starfish such as Anseropoda placenta and anglerfish such as Lophius piscatorius, we mainly found extensive areas of black coral. Due to the risk of entanglement that these fishing line and net remains entail, we took the Rov out of the water and headed for the spot where we made the third immersion of the day, a seamount located at some 2.3 miles off the coast to the north of Sonabia.
This last immersion was made at a shallower depth of about 55 meters. In this case, the bottom was in better condition with quite a bit of diversity of species that live on a mixed substratum, rocky and sandy. Several species of sponges, sea fans, coral, polychaete worms, sea urchins, anemones and hydrozoa carpeted the bottom. However, curiously enough, the absence of fish was once again what marked the dive.