This summer and early autumn, two teams of researchers completed two campaigns monitoring cetacean and marine turtle populations in Canary Island waters as part of a European Spanish-Portuguese project to check their state, with an eye on the second Marine Framework Strategy cycle in the islands in the region of Macaronesia (Azores, Madeira and the Canaries) home to a little-studied fauna treasure.
The project, called Mistic Seas 2, involves collecting data on estimates of the abundance of such species as the loggerhead turtle, various types of dolphin, sperm whales, beaked whales and tropical pilot dolphins, using a common methodology based on sample transects, i.e. places indicated in advance for sightings.
Five researchers (four marine biologists and a geographical data system analyst technician) and a master from the UTE Ceamar-Alnilam-ADS ran an ocean campaign in September and October throughout the Canary Islands archipelago’s waters aboard a vessel a maximum of 12 miles from the coast, and channels between the islands.
Mónica Pérez, manager of the Joint Venture and President of Ceamar explains how the work meant sailing at a constant speed, with two observers scanning the horizon from the prow. “All the data on sightings were recorded, along with environmental conditions such as the state of the sea or visibility, that is, all the factors which might affect the animals”.
Poor sea conditions created a variety of difficulties for the researchers, reducing the number of sightings in October, although Ms. Pérez made it clear that they saw “a couple of very large pods of spotted dolphins, numbering more than 500”.
She explained that the boats sailed through areas known for high concentrations of cetaceans and also through others where data are scarce, so ruling out stating whether climate change is affecting the animals because of rising sea temperatures, in the absence of sufficient data with which to draw conclusions on this aspect.
Average temperatures on the Earth’s surface have already risen to 1.1ºC above their levels in preindustrial times, when the scientific consensus, set out in the Paris Accord, is that the planet must not rise more than 2ºC and even that countries must make the effort to reduce greenhouse gases so as not to exceed 1.5ºC, the threshold above which irreversible consequences may be unleashed in climatic patterns, as is already happening with episodes of devastating effects in many parts of the globe (cyclones, loss of Antarctic and Arctic marine ice, floods, heat waves, drought, hurricanes, etc.).
“There were few sightings in September, very strange compared with what we were expecting, and our experience in previous years, but this meant nothing because there were more in October. Were this project to be repeated year after year we would, in 10 years, be able to see a tendency. There are no existing data making it possible to study the long-term trend”, and adding, “It is impossible to know if climate change is affecting species”.
It must however be made clear that the researchers did see “something surprising”: two large pods of spotted dolphins, one in the north of Lanzarote and the other in La Palma, which also occurred in Madeira. Loggerhead turtle sightings were not numerous because of the state of the sea, an obstacle to the probabilities of seeing this species in the water.
The biologists were able to move outside the pre-set transect if at less than 15 minutes or within a range of less than two miles when detecting the presence of cetaceans or turtles, to facilitate their identification. There were during the long hours of work specimens that swam close to the boat, and others further away, making it necessary to sail toward them. “It was normal to find them at between four and six kilometres”, Mónica Pérez added.
ON A ZODIAC SOUTHWEST OF TENERIFE
On the other hand, as part of the Mistic Seas 2 project, a coast campaign was also carried out by the Society for the Study of Cetaceans in the Canary Archipelago (SECAC) in the Teno-Rasca Marine Strip Special Conservation Zone covering the entire southwest of the island of Tenerife.
The SECAC researchers sailed aboard a zodiac on 32 days between August and October, covering 1,800 kilometres and with sightings of seven species of cetaceans and loggerhead turtles, distributed as follows: 90 of turtles, 53 of pilot dolphins, 29 of bottlenosed dolphins, 5 of spotted Atlantic dolphins and one of striped dolphins, Fraser dolphins, sperm whales and beaked whales. They also caught 21 turtles, three of these ending up in a marine fauna recuperation centre (‘La Tahonilla’, northern Tenerife) because of driftnet lesions. One specimen had a hook through its mouth.
First thing every morning, the SECAC researchers boarded the zodiac in the port of Los Gigantes and, after noting the environmental conditions for the day, began work. For each sighting, they recorded the species, the numbers, and various data. Pilot whale populations were greatest in the marine zone overlooked by El Teide, surrounded by a variety of microclimates, from clouds to clear skies, occasional light showers and sometimes swell rippling the Atlantic waters.
Spotted dolphins pods, more timid, appeared at a distance from the zodiac, sometimes with flocks of shearwaters looking on from the tops in search of trumpet fish for food. On the other hand, pilot whales swam and dove fearlessly, sometimes even approaching the zodiac to stop with half their bodies submerged so that it was possible to hear their breathing, until they went on their way, frolicking on the water.
Martín, a cetologist with 30 years’ experience, enters the debate on climate change, affirming that “the heating of the ocean will lead to a loss of biodiversity in the planet’s tropical and subtropical zones, and an increase of temperature in the temperate and cold areas where the tropical species will head”.
“We have had many more sightings in all the campaigns, and in this one we came across fewer bottlenosed dolphins. In the last 10 years, the average pod number size has dropped, which we attributed to the pressure of human activities and deterioration of the habitats. It used to be very common to see pods of 30 or 40, but now they are much smaller”.
He stated that, “in this campaign, subjectively speaking, we have noted fewer sightings of bottlenosed dolphins, without knowing whether this is exceptional or a coincidence”, adding that, “they are more elusive with the boats than in other years and it is very difficult to investigate them”, agreeing that populations of these marine species in the Canary Islands must be investigated medium- and long-term.
CAPTURE AND RELEASE OF TURTLES
A special feature of the SECAC campaign is the capture of loggerhead turtles. When the researchers detected a specimen resting on the surface, Vidal jumped into the water to catch it. Once aboard the zodiac, they carried it to a nearby port where blood and tissue samples were taken, a microchip was fitted if not already in place, to make its movements available to the public on various websites (e.g. ‘siare.herpetologica.es’ and ‘www.seaturtle.org’) and various biometric data were taken, of weight and body measurements. The animal was then released into the sea.
Young loggerhead turtles reach Canarias, up to four years of age, usually born in Florida in the United States or in Cape Verde. According to Carmen Meléndez, a Secac oceanographer, “They are very hard to catch because they are very timid. Any movement or sound they note sends them down, we lose them, and they do not surface again”.
The work of the marine biologists is, like that of so many scientists, an entire rollercoaster of sensations. “It is hard work, people have a romantic view of research, but campaigns at sea are difficult. To get results, there must be many hours of research”, in Vidal’s words.
The Mistic Seas 2 project is helping to fill the continuing gaps in study in one of the planet’s richest areas of biodiversity. Hours of dedication in the archipelagos of the Azores, Madeira and the Canary Islands will bear fruit with a little more understanding of the mammal, turtle and sea bird populations, reappraising the wealth of Macaronesia thanks to the alliance of the Spanish and Portuguese governments.
