The Tagides are the group of common dolphins that is often seen in the Tagus river. These don’t have nothing to do with the resident population in the Sado’s Estuary! Those are bottlenose dolphins, a quite different species.

Who they are?

They’re usually composed mainly by pregnant females (4^th trimester ) and females carrying very young babies. Occasionally accompanied by females with grown babies and males. They are dolphins found in the usual dolphin areas off Lisbon, but in certain months do regular visits to the Tagus river.

What they do?

They spend 70% of their time feeding or foraging. The remaining time is mostly traveling in and out of the river and rarely resting or socializing.

Background

It is known in the Lisbon folklore there were dolphins in Lisbon in the past. As the story tells, they went away in the 70s due to the increasing pollution in the Tagus river.

Before the founding Lisbon Dolphins, back in 2014 APCM (Association for the Sea Sciences) we dug in depth into the records trying to find support for this old Portuguese mystery.

Several records in journals and magazines were found, referring to dolphins sighted in the Tagus River in the 20 century and even in the 19 century and reporting frequent sightings of dolphins in the Tagus and Sado rivers. There were even older records, going back to the 16 century and the sighting aren’t only restricted to Lisbon, there are records of dolphins seen travelling as far as 40Km upriver!

I seems that dolphins always visited the Tagus river, it was the human perception that shifted away from the river. However these were just occasional visits, even us met dolphins in the river once in a while during our tours back in pre-pandemic years.

However nothing like what happened in 2020 was ever recorded before. The frequency of the visits skyrocketed during the pandemic! With dolphins in the river day after day.

Present data

But all that is now decreasing… For the past 3 years under intensive monitoring, we’ve noticed less and less months with the presence of this group. While in 2023 we’ve got visits for 7 months straight, 2024 got 81% of the sightings within 9 consecutive weeks (~2 months). In 2025 we’ve registered the longest absence period on their visiting period and a big shift in the group composition, with most of the original individuals missing.

Where did the name came from?

Tagides are the name of the Tagus’ nymphs, from which Luís Vaz de Camões asked for ‘sublime inspiration’ to write the Lusíadas, a widely recognised epic poem written in the 16^th century. Who knows if these nymphs were actually dolphins… but definitely these Tagides from today, can inspire the conservation of the biosphere in the Tagus river.

Meet the Tagides

The most sighted individuals also got names from known ocean nymphs from Greek mythology.