Bad memory? New MARE exhibition debunks this and other fish myths
On display at the Museu do Mar Rei D. Carlos in Cascais, the exhibition "Fish Intelligence: Behavioural Complexity in an Underwater World" takes visitors inside the minds of fish. Built on years of research at the Laboratório Marítimo da Guia, MARE | ARNET, it challenges everything we thought we knew about these animals.
João Rocha, director of the Museu do Mar, sees the exhibition as a bridge between science and the public. "This exhibition represents a partnership between the municipality of Cascais and the University of Lisbon in bringing knowledge and democratic access to culture and science," he says, noting that Cascais holds the title of European Capital of Democracy this year. He also thanked Teresa Crespo for her role in bringing the exhibition to the museum.
The exhibition was curated by José Ricardo Paula, principal investigator at the Behavioural Complexity Laboratory at the Laboratório Marítimo da Guia, MARE | ARNET, and professor at the Faculty of Sciences of the University of Lisbon, who is quick to describe it as a team effort. The watercolour illustrations across the seven panels are by Lia Neves. Lisandra Tavares, a master's student, developed the written content and created the crochet pieces on display. Raúl Oliveira produced the 3D-printed animal brains. Patrícia Pinto appeared in the video on display and helped install the exhibition, while Luís Almeida contributed to the biological descriptions that guided the illustrations. The documentary that closes the visit was directed by Vasco Pissarra.
Panel by panel, the exhibition takes apart the assumptions we carry about fish. It opens with a question that turns out to be trickier than expected: what actually is a fish, from an evolutionary point of view? From there it moves into their senses, which are, as the panels put it, "very different from our own," ranging from the electroreception of sharks to the lateral line, a sensory organ that works as a kind of touch at a distance.
Visitors are then invited into the minds of fish. The 3D-printed brains on display let you compare brain structures across wildly different species, from fish to crocodiles to humans. The next panel tackles one of the most stubborn myths about fish, familiar to anyone who grew up watching Finding Nemo. "There is a widespread assumption that fish have a three-second memory. That is simply not true. We have evidence of fish retaining memories for more than two years," says José Ricardo Paula, pointing to experiments conducted at his own lab on fish self-awareness tracked over the course of a full year.
From memory, the exhibition moves on to social life. José Ricardo Paula walks visitors through the surprisingly complex rules of cleaning stations, where small cleaner fish negotiate with, and occasionally nip, their client fish. He also describes what he considers one of the most remarkable examples of animal cooperation: groupers and moray eels hunting together, each making up for what the other cannot do, to flush out prey hiding in coral reefs.
Then comes the mirror test. Cleaner fish, upon spotting a mark on their chin reflected in a mirror, try to scrape it off against a rock, a behaviour long thought to be exclusive to a handful of mammals and birds. "This tells us they recognise their own facial features, much as we recognise our own," says José Ricardo Paula.
The visit ends on a harder note. Climate change and overfishing are eroding entire cultures within fish populations. José Ricardo Paula recalls the case of Norwegian herring, where older, larger fish carry the knowledge of where to spawn and pass it on to younger generations. Fishing those individuals out of the population wiped out that knowledge, and the herring stocks stopped following the Norwegian coast, drifting instead into the middle of the North Sea. What began as a biological problem became a political one, now shared between several countries including Iceland and Scotland. "You can catch the big fish, but the big fish cannot pass on culture and social community if they are no longer there to do so," he warns, adding that headcount alone tells you nothing about the health of a population's collective knowledge.
Jorge Marques da Silva, Vice-Dean of the Faculty of Sciences of the University of Lisbon for Teaching and Pedagogical Innovation, points out that the exhibition connects with parts of the faculty that might not seem obvious at first. "In our bioethics course we discuss the cognitive capacities of different organisms, because ethical theories of animal protection hinge on precisely those capacities, and that feeds directly into legislation," he says. He expects the exhibition to travel to the Faculty's Science Gallery, where he hopes it will also draw in students of Psychology and Medicine.
Bernardo Duarte, coordinator of MARE ULisboa, notes that this is already the third exhibition brought to Cascais by research groups from the Laboratório Marítimo da Guia, following previous shows on climate change and corals. He sees this track record as evidence of a deepening relationship between MARE and the municipality, and hints that after a stop at the Faculty of Sciences, the exhibition could visit other MARE nodes, with a digital version also on the table.
Behind the panels lies a less visible body of work in illustration and design. Lia Neves, who created the watercolours throughout the exhibition, recalls that José Ricardo Paula's invitation arrived just when she was looking for a project connected to the sea. She chose watercolour because it is, in her words, "one of the most demanding techniques" and because it felt right for something as fluid as the ocean. The harder challenge, though, was conceptual: "I had to think about nature as if I were making a comic strip," she explains, describing scenes like a cleaner fish gently stroking a client to keep it cooperative. The exhibition also features illustrations by Marta Herrero Castro, who drew species including tuna, parrotfish and pufferfish.
Beatriz Palinhos Pereira, who led the exhibition's design, admits it was new territory for her. "The challenge was having a plan and actually sticking to it," she says. The visual concept shifted along the way, moving from dark panels with line drawings to a final look inspired by a laboratory notebook, complete with handwritten text and hand-drawn arrows, once Lia Neves's colour illustrations made the dark background feel unnecessary. She sums up what she hopes visitors take away in a single line: "that fish are intelligent and that good science is done in Portugal."
The exhibition also features fish sounds curated by the Fish Bioacoustics Lab of MARE | ARNET at the Faculty of Sciences of the University of Lisbon, produced by Manuel Vieira, Clara Amorim and Paulo Fonseca. It is supported by the Luso-American Foundation for Development (FLAD), the "la Caixa" Foundation and the Foundation for Science and Technology (FCT).
Useful Information
Fish Intelligence: Behavioural Complexity in an Underwater World
Open to the public: until September 14, 2026
Venue: Museu do Mar Rei D. Carlos, Cascais
Text: Vera Sequeira
Photography: Patrícia Chaves and Jéssica Jacinto