2022: The year of the Sei whale

by Enrico Villa

For the joy of our passengers and crew, summer 2022 in Pico was characterised by an unprecedented high number of Sei whale sightings.

Sei whale breathing at the water surface

Sei whale breathing at the water surface (photo by Enrico Villa)

Blue whales (Balaenoptera musculus), Fin whales (Balaenoptera physalus), Humpback whales (Megaptera novaeangliae) and Sei whales (Balaenoptera borealis) are the baleen whale species we see most often in Pico. Among these, Blue and Fin whale sightings have historically been the highest.

However, in the last few years a trend began to emerge, as we witnessed an increase in Sei whale sightings and a decrease in sightings of Fin whales.
You can check this fact by using the charting tool on our website, where yearly and cumulative species-specific sighting charts are dynamically created and updated, based on the data collected from our boats.

The throat grooves (also known as throat pleats) of a Sei whale

The throat grooves (also known as throat pleats) of a Sei whale (photo by Enrico Villa)

Baleen whales belong to suborder Mysticeti of the Cetacea order and have always been the main subject of our self-funded scientific research.
We see them mainly in spring, when they pass by the Azores on their way to the high-latitude, summer foraging grounds - places like Iceland, Norway and Greenland. You can read a blog post about baleen whale migration in the Azores here.

One notable exception to this migratory pattern is the Bryde's whale (Balaenoptera brydei), whose seasonal, latitudinal movements are far more contained than those of the other members of family Balaenopteridae, to the point that one could say Bryde's whales do not migrate.

It is interesting to note that we never had a Bryde's whale sighting in spring, with all encounters recorded between July and October. On the other hand, Sei whale have often been seen in spring and sometimes also in the summer.

Things started to change in 2020, when Sei whale sightings in the summer went up considerably, Unfortunately, we cannot tell whether Sei whales were also more present in spring, since in 2020 Covid-19 kept us on land until the end of June.

The trend continued in 2021, with twice as many Sei whale sightings between July and October as those recorded between March and June.

In 2022 Sei whale encounters rocketed up, with only 7 sightings between March and June and 101 (!!) sightings between July and October, something absolutely unprecedented!

In many of these encounters Sei whales were observed feeding on fish, with Atlantic horse mackerel (Trachurus trachurus) being the prey in numerous occasions.

Sei whale absolute number of sightings in 2022

Absolute number of sightings: the number of boat trips in which we saw the species.

Along with the absolute number of sightings, our charting tool also provides you with a view based on the relative number of sightings.

% Sightings (relative number of sightings): the proportion of boat trips in which we saw the species, out of the total number of boat trips we ran.

Sei whale relative number of sightings in 2022

To get things into perspective, the Sperm whale (Physeter macrocephalus) is the species we see more than any other in Pico.

Historically, between July and October, the proportion of Sei whale sightings to Sperm whale sightings was 13%. In 2022, the same proportion between July and October climbed to 69%!

We do not know whether this trend will consolidate in 2023, neither do we know why Sei whales spent such a long time in our waters in summer 2022.
Exceptional food availability, perhaps? Poorer foraging conditions elsewhere? And could this be a tangible effect of climate change? These are all questions that need to be addressed.

As a general note, we also need to point out that a huge number of sightings does not necessarily translate into a large number of individual whales, as we could have seen a relatively small number of whales over and over again. We are currently analysing our photo-identification data to shed some light on this.

The snout of a Sei whale

The snout of a Sei whale (photo by Alice Generi)

What we know for sure is that Sei whales are very flexible when it comes to diet. They can feed on both krill and fish. Interestingly, their baleen plated are fine enough for Sei whales to be able to also feed on copepods - crustaceans that are much smaller than krill.

This could perhaps partially explain why the increase in baleen whale sightings we observed in summer 2022 occurred with Sei whales. The amount of food available in the Azores may simply not have been enough to sustain a bigger species such as the Fin whale. As for Blue whales, although even bigger, they feed almost exclusively on krill, so that fish is not a sought after food source for them.

When it comes to species identification, it is not always easy to tell a Sei whale from a Fin whale at sea. When the lower jaw on the right-hand side is visible, it appears white in Fin whales and uniformly dark in Sei whales, which allows for positive identification. The problem is that whales do not often show their lower jaw, so that other distinctive features must be used.

Sei whales often, but not always, feature one of two distinctive dorsal fin types, which are rarely observed in other baleen whale species:

TYPE 1: Large, with an upright trailing edge

A Type 1 dorsal fin of a Sei whale (upright trailing edge)

Photo by Justin Hart

(see Sei whale photographs for Type 1 dorsal fin above and Type 2 dorsal fin below).

TYPE 2. Very falcate and pointy

Type 2 dorsal fin of a Sei whale (very falcate and pointy)

photo by Justin Hart

Another peculiar characteristic of Sei whales is their generally shallow angle of approach to the water surface, so that you can often see the blowholes and the dorsal fin at the same time.

Blowholes and dorsal fin visible at the same time in a Sei whale

Blowholes and dorsal fin visible at the same time in a Sei whale (photo by Justin Hart)

Other baleen whales take a much steeper angle of approach to the surface, so that they start arching their back earlier. The result is that the blowholes are already submerged once the dorsal fin becomes visible.

We at CW Azores offer special holiday packages in spring to see baleen whales. Of course, you may be lucky and see some of them also in the summer, especially Sei whales. However, spring is truly prime time to meet the biggest of all giants, including the mighty Blue whale, which is the biggest animal that has ever lived!

Spring Whale Watching holidays

- BLUE WHALE MIGRATION (English | German | Italian)

- GIANTS OF THE SEA (English | German | Italian)

By purchasing one of the above packages you will you enjoy breathtaking encounters with baleen whales. Furthermore, you will help our research and learn a lot more about whales and dolphins, as our spring special programmes also include lectures.

We wish you a Whale of a Time! 😃