The census, developed from the IbizaPreservation Blue Crime Classroom of the UJI, detects less biodiversity, biomass and presence of adult fish on the Ibiza coast than in areas such as Dénia
December 26, 2025 – A scientific study integrated into the MarPITIUS25 project of the IbizaPreservation Blue Crime Classroom at Jaume I University warns that the Ibiza coastline is in a compromised ecological situation, even in areas where Posidonia oceanica seagrass meadows remain structurally well-preserved. The results of the visual fish census, carried out by researchers from the University of Alicante and Jaume I University , show communities dominated by small and juvenile fish, with a reduced presence of adult individuals and low biomass.
The study includes a direct comparison with equivalent censuses carried out in Dénia, where the same methodology was applied. This time, the results show greater biodiversity, more commercially important species, a more balanced size structure, and a significantly higher biomass than that of the Ibiza coastline.
The fieldwork was carried out in June 2025 in three representative areas of the Ibiza coastline —Santa Eulària, Cala Sol d’en Serra, and Talamanca—coinciding with a period of peak tourist and environmental pressure. A total of 3,243 individuals belonging to 15 species were recorded, a small number for this type of habitat, especially when compared to other areas of the western Mediterranean, according to the University of Alicante and the UJI.
“Underwater, in the sampled areas, we found an ecosystem that is not functioning correctly : small and juvenile fish predominate, and there are hardly any adults. This allows us to infer that there is ongoing environmental pressure, even though the Posidonia seagrass meadow is still standing,” explains Esteban Morelle-Hungría , principal investigator of the project and director of the IbizaPreservation Blue Crime Classroom at Jaume I University.
“When we compare Ibiza with other points in the western Mediterranean, such as Dénia, we observe fewer species, less biomass, and fewer adult fish. This indicates that the ecological state of the Ibizan coastline is more fragile than is generally assumed ,” Morelle points out.
In Ibiza, almost 98% of the individuals observed were small in size , compared to a much smaller proportion in Dénia, which reinforces the idea that large areas of the Pitiusan coast function mainly as breeding areas , a criterion of great relevance when identifying possible locations for a Marine Protected Area (MPA).
A silent and cumulative degradation
Researchers warn that these results are not due to a single incident, but rather to the accumulation of environmental pressures that constantly affect the coastline. These include spills, brine from desalination plants, microplastics, heavy maritime traffic, and high levels of tourism. “One of the biggest problems is that marine environmental damage has become normalized. Legal spills, poorly located infrastructure, or intensive tourism are not perceived as violence, even though their effects are clearly destructive,” warns Morelle-Hungría.
From the perspective of Blue Criminology, the study introduces the concept of slow environmental violence , a type of degradation that does not occur abruptly, but whose effects accumulate over time.
“What this data shows is not an accident or an isolated incident, but a slow and cumulative form of environmental violence . The damage to the Pitiusa Sea does not happen suddenly, but occurs day by day, without visible culprits and with real consequences for the ecosystems,” adds Morelle-Hungría.
The fish census constitutes a key biological baseline for guiding future conservation and management policies for the Ibiza coastline. Among the study’s main recommendations are the implementation of regular monitoring programs , the review of the design and location of outfalls, the application of the precautionary principle in water management, and the evaluation of new marine protected areas . “Blue Criminology doesn’t come into play when the damage is already irreversible, but rather to prevent it. Studies like this allow us to identify risks, correct decisions, and prevent marine degradation from becoming permanent structural damage ,” the researcher concludes.
The IbizaPreservation Classroom for Blue Crime, jointly promoted by the IbizaPreservation Foundation and the Jaume I University of Castelló (UJI), is an academic space dedicated to the study, research, and dissemination of information on ecological damage to aquatic ecosystems. Using an interdisciplinary approach based on Blue Criminology, the Classroom analyzes practices such as dumping, overfishing, and habitat destruction, considering both their ecological impact and their potential legal implications . Within this framework, the MarPITIUS25 project is being developed, integrating physicochemical and biological data to offer a scientific, legal, and restorative diagnosis of the Ibiza coastline, with the aim of contributing to fairer and evidence-based environmental governance.
