With the arrival of capelin, we have been seeing a rich diversity and abundance of cetaceans in Faxaflói over the past couple of weeks. To summarise our sightings (you can read more about our daily encounters in our Whale Diary), we have seen superpods of white-beaked dolphins, multiple humpback whales, many harbour porpoises, a few minke whales, and on the 23rd of March we even saw a fin whale! Although encounters with fin whales are already unusual (these whales are mostly found offshore), this sighting was even more unexpected because we saw the blow after less than half an hour of sailing from Reykjavík! What made the encounter even more special was that the fin whale was surrounded by a superpod of over 100 white-beaked dolphins, which were feeding in association with a diversity of seabirds and leaping out of the water all around our boat. After this unique sighting with the fin whale, we want to dedicate this blogpost to the world’s second-largest animal and explain a bit more about their biology.
The fin whale with Reykjavík in the background – photo by Megan Whittaker
What’s in a name?
Fin whales received their name because of their prominent dorsal fin. Of course, many whales have dorsal fins, but the people who named the fin whales were used to seeing bowhead whales and right whales, so comparatively the fin whale’s fin was very conspicuous. In Icelandic, the fin whale is called langreyður, which means long rorqual. Fin whales certainly are long, with an average length in the Northern hemisphere of about 20 meters. The second part of their Icelandic name, rorqual, means that they have longitudinal grooves in their throat that allow them to open their mouth extremely widely in order to capture as much prey as possible. The Latin name for fin whale is Balaenoptera physalus, which more or less translates to “blowing winged whale” – a name which they received thanks to their impressive blow which can reach 6 meter in height.
The fin whale’s impressive blow – photo by Megan Whittaker
How to identify a fin whale?
Fin whales look similar to their close relative the sei whale, but there are some characteristics that distinguish the two species. Firstly, fin whales are bigger than sei whales. However, in the water it is challenging to gauge a whale’s size and individual variability makes length an unreliable indicator for species identification. An easier way to distinguish the two whales is by their dorsal fin: for fin whales, the dorsal fin flows in one line from the back so you almost don’t see where the dorsal fin starts and the back ends, while the sei whales’ dorsal ridge is not as flowing (see photo below).
The most reliable visual identification is made possible by one fin whale characteristic that no other whale has: an asymmetrical jaw colouration. The lower right jaw and baleen plates of fin whales are white while the lower left jaw and baleen plates are dark! Fin whales might flash the white side towards their prey while they are hunting to surprise them, because white can be a striking colour in the dark water and may shock the fish and zooplankton.
Front view of a fin whale, showing the asymmetrical colouration of the jaw. – Annie Douglas
Is it a fin whale or an earthquake?
Fin whales, together with blue whales, make the lowest frequency sounds of any whale species. These calls are so low, that the first time they were recorded scientists were so confused that they thought they were listening to the grinding of two tectonic plates. The sounds of fin whales are also incredibly loud, sometimes reaching 190 dB! These calls can travel far through the water to impress females during the mating season, or they may be useful during foraging.
Fin whale on the 23rd of March 2022 - photo by Eline van Aalderink
Our encounter with the fin whale shows us that nature is full of surprises: when we sailed out, we never expected to find a fin whale so close to Reykjavík harbour. We are happy to have shared this special moment with our passengers, and also excited to have gathered some photographic data of the fin whale. Even though fin whales are harder to identify than the humpback whales and minke whales that we regularly see on our tours, we will submit this individual to our database and keep track of any future sightings.
By Eline van Aalderink