Ocean Conservationist Tiago joined the Brittany Ferries’s Salamanca, sailing between Rosslare and Bilbao, at the end of April. He shares with us some of his sightings and the struggles of being a cetacean in 21st century.
Like most people, I assume, when I was getting ready to embark on this journey, one of the first things I did was to write a sightings wishlist. I studied the Bay of Biscay extensively in the past, so I knew all about how bountiful in can be, at least in theory. Even so, witnessing the richness and diversity of the bay – and the Celtic Sea - this early on in the season was astonishing. It is true that it started off a little slow, but as soon as we got into late May things started to pick up beautifully.
Unlike the Bay’s reputation would have you believe, it can be very calm during the summer, and I was lucky enough to have mirror-like conditions throughout the best part of June. This allowed me and the guests on board the Salamanca to spot loads of smaller cetaceans – such as harbour porpoises (Phocoena phocoena), common dolphins (Delphinus delphis) and striped dolphins (Stenella coeruleoalba). There were days when we got impressive shows, from pairs or trios of common dolphins breaching and engaging in playful behaviour, to large pods milling (when cetaceans swim very slowly, changing directions at random, in a restful state).
Whales made their daily appearances as well, for example, I spotted one splendid fin whale (Balaenoptera physalus) and several Minke whales (Balaenoptera acutorostrata), a familiar species to some of the Irish passengers. Besides that, the elusive Cuvier’s beaked whales (Ziphius cavirostris) have been a fairly common sight in the Bay - on their own or in pairs of mother and calf -, with some of them popping out within a 50-meter radius of the ship, giving everyone a good look at their peculiar beak and large grey bodies.
One of the cetaceans that I was most eager to spot, one which was on my wish list precisely for being so evasive, was the Risso’s dolphin (Grampus griseus). This is the fifth largest dolphin species in the world and although they are not usually included in the informal Blackfish group, they are genetically related to those species, such as the false killer whales (Pseudorca crassidens) and pilot whales (Globicephala spp.). Risso’s dolphins have a particularly bulbous melon, and a blunt beak and adult males can usually be identified by the distinctive scars, which make their bodies appear white. These are usually a result of territorial or mating disputes, and scientists believe that a heavily scarred body might be a deterrent to further challenges by other males.
Even though the Risso’s dolphin tends to inhabit the steep shelf-edge areas, of which the Bay of Biscay is a great example, they are typically shy and spend a lot of time underwater during their deep dives (up to 600m of depth), which can make them a rare sighting. In fact, the circumstances under which both sightings occurred were particularly unlikely. I spotted the first Risso’s dolphins of the season during one of our arrivals to Rosslare, that is, in extremely shallow waters, while a couple of weeks later I sighted a pod of four, approaching the ship while crossing the Bay of Biscay. Although uncommon, this type of behaviour has been seen in other cases, such as that of the famous Pelorus Jack, a Risso’s that would follow ships off the coast of New Zealand, in the late 18th century. As a result, in both cases it actually took some careful studying of the photos available to arrive at a conclusive identification.
These unexpected circumstances hint at how much there is left to discover from these animals, and how challenging it can be to describe their behaviours and networks. As a matter of fact, the distribution of the European population of Risso’s dolphin is unclear and the IUCN still considers this population data deficient. This also highlights the importance of the data gathering effort ORCA is conducting, in order to help policymakers understand the location of cetacean hotspots and the range of habitats of the species we have in European waters, and thus protect these animals and our marine ecosystems.
While the IUCN considers the global population to be of least concern at the moment, Risso’s dolphins are susceptible to many anthropogenic threats. One study of the Adriatic Sea population showed more than half of the individuals examined to have high mercury concentrations which the experts considered an indication of liver damage (Sedak et al., 2022). Other authors also found high concentrations of other contaminants, such as PCBs in other populations of the Mediterranean Sea (Minoia et al., 2023). Like many of the other large species, Risso’s dolphins are a top predator with a long lifespan which means that contaminants in the marine environment are accumulated in their system throughout their long lives.
In a more direct way, Risso’s dolphins are part of the group of species still being hunted down by humans in some parts of the world, namely, in Sri Lanka, Taiwan, the Caribbean and in the infamous Taiji bay in Japan. Unfortunately, even non-lethal activities can have harmful impacts on these cetaceans. Visser et al. (2010) showed that for a population in the Azores, a location famous for whale-watching, the increase in touristic vessel traffic during the high season led to a reduction in the amount of time spent resting and socialising. The increase in stress from irresponsible whale-watching and “swim-with” activities has also been observed in other cetaceans (Pacheco et al., 2021), which is why ORCA developed its own guidelines for responsible whale-watching, which we always advise guests to take in consideration when booking their trips.
We humans have the incredible power and tools to protect these animals and make sure that the next generations can witness the Risso’s dolphins and all of the other 24 species of cetaceans that inhabit European waters, and I am excited to be part of that effort. You can join us too by downloading our App, registering for our Marine Mammal Surveyor course, and becoming a citizen scientist for marine conservation.
Minoia, L., Consales, G., Mazzariol, S., Mancusi, C., Terracciano, G., Ceciarini, I., Capanni, F., Neri, A., D’Agostino, A., & Marsili, L. (2023). Preliminary assessment of Persistent Organic Pollutants (pops) in tissues of Risso’s dolphin (Grampus griseus) specimens stranded along the Italian coasts. Marine Pollution Bulletin, 186, 114470. https://doi.org/10.1016/j.marp...;
Pacheco, A. S., Sepulveda, M., & Corkeron, P. (2021, August 13). Whale-Watching Impacts: Science, Human Dimensions and Management. Frontiers in Marine Science.
Sedak, M., Bilandžić, N., Đokić, M., Đuras, M., Gomerčić, T., & Benić, M. (2022). Body burdens and distribution of mercury and selenium in bottlenose, striped and Risso’s dolphins along the Adriatic Coast: A 20-year retrospective. Marine Pollution Bulletin, 185, 114298. https://doi.org/10.1016/j.marp...;
Visser, F., Hartman, K. L., Rood, E. J., Hendriks, A. J., Zult, D. B., Wolff, W. J., Huisman, J., & Pierce, G. J. (2010). Risso’s dolphins alter daily resting pattern in response to whale watching at the Azores. Marine Mammal Science, 27(2), 366–381. https://doi.org/10.1111/j.1748...