The research, which is being carried out using tracking drones, aims to find out the navigation patterns of this species in order to predict when and where they might arrive on the Canary Islands' coasts.
The University Institute for Research in Sustainable Aquaculture and Marine Ecosystems (ECOAQUA) of the University of Las Palmas de Gran Canaria (ULPGC), through the Ecophysiology of Marine Organisms (EOMAR) group, has started the first observation campaign of the frigate or Portuguese caravel (Physalia physalis) in the waters of Gran Canaria within the framework of the PHYSALIA project in which the Asturias Marine Observatory of the Department of Biology of Organisms and Systems of the University of Oviedo (UNIOVI) and the Institute of Marine Sciences of Andalusia, through the Higher Centre for Scientific Research (ICMAN) are also participating.
The ‘Evolution of Biological Sailing’ project, whose acronym is PHYSALIA, aims to analyse the navigation patterns of Portuguese caravels in order to understand their evolution and improve predictions of their arrival at the coast.
Thus, in addition to navigation patterns, the PHYSALIA project aims to shed light on the biology, spatial distribution and mechanisms that determine the seasonality of this organism, a relative of jellyfish, of which very little is known and which, nevertheless, frequently arrives on the Canary coasts, causing the well-known inconvenience to bathers on the beaches.
For this purpose, an interdisciplinary team of oceanographers, evolutionary ecologists, engineers and modellers are making in situ observations of Portuguese caravels at sea and will model these observations.
A snapshot of the drone tracking of one of the specimens of Physalia or Portuguese Carabela with the researchers' boat.
The resulting navigation models will then be combined with other variables such as wind, sea currents and the size of the caravels to build agent-based models (MBAs) that simulate the population dynamics of this species in a virtual ocean.
This first observation campaign will continue until 17 March this year in different locations on the island of Gran Canaria, such as Las Canteras and Taliarte.
Monitoring with drones in a unique initiative
Since this week, drone flights have already been taking place to track the caravels in order to determine their navigation trajectories. The procedure is carried out with a drone in a zenithal position over a caravel at the lowest possible height without disturbing the wind conditions on the surface, recording its position, the orientation of the sail and the behaviour of the colony for 10 minutes.
This is, says May Gómez, director of EOMAR and principal investigator of the project on behalf of ECOAQUA, a novel scientific initiative. ‘There is only one precedent dating back 70 years, in which English researchers monitored a few Portuguese caravels by boat in the waters off Tenerife. Since then, no similar project has been developed, although these initial observations are still used today to predict the arrival of these dangerous animals. In this project, monitoring is carried out with drones and drifting buoys equipped with wind and current sensors to understand the mechanics of how these frigate birds move and how they do it.
Physalia or Portuguese caravel.
Unlike the pioneering study, where only a few individuals were observed, the aim of this research in which EOMAR is participating is to try to follow approximately 50 individuals. ‘This number will give us a statistically replicable figure for their observation,’ says Gómez.
‘This tracking is very important because knowing how they move, what speed they reach thanks to the wind and how they move, will help us to know why they reach our coasts and, above all, what is even more important, to predict when they will reach the coasts and at what locations thanks to the prediction models that we will obtain after these observations,’ adds the ECOAQUA researcher.
EOMAR is collaborating in the monitoring with drones, observing their movements and providing data on their biological structure. ‘We have specimens in culture, fed for the first time in a controlled environment for 21 days, and this provides us with information on the physiology and biological mechanisms of this species before releasing them back into the ocean and observing how they navigate’.
One of the researchers accesses the buoy equipped with sensors while the drone is in flight.
At the end of the observation, underwater photographs of the tentacles of these frigatebirds are taken from an inflatable boat to determine their dimensions. Afterwards, each specimen is taken out of the water and various morphometric measurements are taken.
This species is very delicate, so it is impossible to place sensors on them. For this reason, says Gómez, in a second phase, ‘we are going to try to develop replicas of Physalias that navigate in a similar way to the ones that will be able to be sensorised’.
The project, funded by the State Research Agency of the Ministry of Science, Innovation and Universities of the Spanish Government, has a deadline of 31 August 2027 and has the collaboration of the REDPROMAR sightings network. In addition to May Gómez, researchers José Luis Acuña and Fernando González Taboada from the University of Oviedo and Laura Prieto from the Institute of Marine Sciences of Andalusia are participating as PIs in the different subprojects.