Thousands of Fish Identified in Alicante Reservoirs Using 3D Sonar Technology

The Department of Environment, Infrastructure, and Territory has implemented a state-of-the-art 3D sonar system that allows real-time reading ('Forward Facing Sonar'). This has enabled the identification of nearly 24,000 fish from 16 species in the main reservoirs of the Valencian Community.

With this new system, which allows the observation of the shape and movement of fish, technicians from the Wildlife Service and Natura 2000 Network conducted a survey of the ichthyofauna during 2024, obtaining updated information to be incorporated into the Generalitat's Biodiversity Data Bank.

Additionally, the number of specimens of each species has been quantified (for fish schools in species like the bleak, where the total number of specimens has been estimated), and the depth at which they are located has been recorded, along with the surface water temperature.

Thus, two types of inspections have been carried out: one in deep open waters over 10 meters and another along the shore, counting all fish sighted in both cases. In some instances, technicians had to force the fish to change orientation to correctly identify it, with the assistance of the Hunting and Fishing Service of the Department.

Through this fieldwork, the aim is also to identify species classified as vulnerable to activate conservation programs and, in parallel, to detect the impact of invasive categories in our natural environment.

The field research was conducted over a year in the 20 main reservoirs of the Valencian Community (2 from the Segura Hydrographic Demarcation and 18 from the Júcar).

Of all the fish species detected, the carp was the most recurrent, appearing in 100% of the sampled reservoirs, followed by the 'black bass', detected in 19 of the 20 reservoirs, although there are indications that it is present in 100% of the areas.

Furthermore, the sampling conducted by the Department reveals that in these types of water bodies, exotic species dominate, while native species are difficult to find, tending to disappear as they are mostly old individuals or, in the case of the eel, the result of past restocking efforts.

The only exception is the blenny or friar fish, which maintains abundant populations in the Júcar and Cabriel and requires specific sampling.

The presence of 'Trachemys scripta' or Florida turtle in almost all reservoirs is also notable, with populations clearly on the rise in recent years, along with exotic bivalves like the zebra mussel. Another interesting fact is the discovery of an unknown population of Asian clam, an invasive species, in the Contreras reservoir.