The installation of shelters in three areas of Trafaria Bay is the first stage of an intervention by the D-EVOLUTION initiative in the Tagus Estuary, developed by the environmental association WWF Portugal and involving partners such as MARDIVE – Association for Science and Education for Marine Biodiversity Conservation, and supporting companies such as Lidl Portugal, Solvena and Pastéis de Belém.

These entities promoted a visit to the site to observe one of the monitoring actions of the seahorse population in the area, composed of the common seahorse (Hippocampus hippocampus) and long-snouted seahorse (Hippocampus guttulatus) species, discovered in 2019.

In statements to the Lusa agency, Gonçalo Silva, a scientific diver and researcher responsible for MARDIVE's underwater intervention, explained that although it is difficult to count them, observations since 2019 have made it possible to verify that the seahorse population of Trafaria Bay is Significant.

“We are talking about rare species. As a rule, we see one or two individuals, and here, when we dive for the first time, we find 10, 12 individuals,” he said.

Seahorse behaviour

During the scientific work carried out by MARDIVE on the Trafaria riverfront, he said, seahorses were observed using different artificial structures and debris on the estuary floor, including abandoned supermarket carts, revealing the adaptability of these species in the face of scarce natural habitats to cling to.

Thus, what began as marine debris turned into a lifeline for the species.

In addition to these seahorse species, the marine species "Syngnathus acus," which belongs to the same family, was also observed very frequently in the area and makes up this multi-species community.

“One of the main things that caught our attention was that, amidst all the marine debris that existed here, mostly fishing gear or fishing-related items, there were abandoned supermarket trolleys, and we saw seahorses using these shelters,” he said, adding that the idea then arose to use what seemed to be working.

Transformed trolleys

The supermarket trolleys, he stressed, were transformed with the help of two local metalworkers, thus also involving people from the community.

“We transformed the trolleys in order to prepare them and minimize the risks, removing plastics, creating and welding pieces so that we could stake them at the bottom so that they don't move and thus create these shelters,” he said, adding that this action will now be monitored between 2026-2028 to assess the occupation of the shelters by the target species, the development of associated biological communities, and the ecological evolution of the area intervened.

WWF mentions that the area targeted by the initiative in the Tagus Estuary has deteriorated due to various pressures, including marine litter, pollution, underwater noise, and other human activities that affect the ecological conditions necessary for the survival of these species, such as dredging.