Seahorses released to halt population decline

On 16 November, a group of 60 seahorses (most of them born in captivity) were released into the Ria Formosa.

This is part of a repopulation project called ‘Seahorse’ and is being carried out in the place where just 20 years ago was the largest seahorse community in the world.

In 2000, the community of these fish in the Ria Formosa, Algarve, was considered the largest in the world, but in 20 years "there has been a reduction of 96 percent in numbers", Jorge Palma, a researcher at the Center for Marine Sciences (CCMAR) at the University of the Algarve (UAlg) told reporters.

The animals were released in one of the two sanctuary areas recently created in the estuary, between Faro and Olhão where artificial structures have been placed to recreate their natural habitat so that they can settle there.

Most of these seahorses were born in the tanks of the Ramalhete Marine Station, in Faro, but their parents are specimens that lived in the wild and were taken there in order to breed, thus contributing to the conservation of the species.

The project, "only makes sense because the introduction is made in a protected area, otherwise they would be exposed to negative effects that may still exist in the estuary", stressed Jorge Palma, noting that the objective is that the animals stay in the sanctuary.

The seahorses were transported by boat in two tanks to a protected area, about half a mile off the coast, where sailing is prohibited. They were then carefully placed in small cages to be taken into the water by divers.

The team of divers took the cages to the bottom, at a depth of about four meters, to then release the animals next to the artificial reefs that will become their habitat.

According to Jorge Palma, these fish are “completely different from all the others” and also “poor swimmers”, which makes them “very vulnerable”, as they “have to be always attached to something”.

Although most of the animals released were only between seven months and a year old, they are already adults and during their short life in captivity their ability to survive in the wild has been preserved, he added.

“What we gave them in captivity is not feed, but their natural prey that they have to hunt in tanks, so when they are released, they will maintain this ability to survive in the natural environment”, noted the researcher.


In a month, the team will return to the site to monitor the evolution of the new population, a task made easier by the fact that these fish have, depending on the species, physical characteristics that distinguish them from each other, and allow them to tell the difference between them and the ones already found in the wild.

“Before releasing them, we took pictures of each one and they have a natural marking that allows us to distinguish them”, observed Jorge Palma, explaining that the “hippocampus hippocampus” (a species with a short snout) have a marking on the top of the head and the “hippocampus guttulatus” (a species with a long snout) has a pattern of spots on its body.

The population of seahorses in the Ria Formosa has suffered a drastic reduction in recent decades, having almost disappeared due to factors such as environmental changes, the destruction of seagrass meadows, their habitat, illegal fishing, or excessive traffic of boats.

The initiative to repopulate seahorses in the Ria Formosa was carried out by CCMAR under the 'Seahorse' project, with funding from the Belmiro de Azevedo Foundation.

The project will also investigate the dynamics of seahorse populations and try to understand the role of seagrasses as supportive habitats and food providers.

Another of its objectives is to find out if this role of seagrasses could be affected by the recent invasion of the Ria Formosa by the alga “Caulerpa prolifera”.

The project also involves the maritime authorities, the Institute for Nature Conservation and Forests (ICNF), the Ria Formosa Natural Park and the Portuguese Environment Agency (APA).