Sick dolphins

Striped dolphins frequent Pals Beach, following the shoals of bluefish.. But this time we've found one in the sand.

Last November, we came across this striped dolphin. -Stenella coeruleoalba-, died on the edge of the Natural Park, on Pals Beach. Once the emergency services had been alerted, the team of Clinic and Rescue of the @fundaciocram, has transferred it to the Autonomous University of Barcelona (UAB), to determine the causes with a post-mortem.

This dolphin lives far offshore, from 10 miles out, in depths exceeding 150 metres. In areas such as the Costa Brava, where the continental shelf is narrow and steep, it is often encountered closer inshore, following a school of bluefish. This dolphin is distinguished by its white or pink ventral underside, with one or two dark blue bands running from the eye to the anal fin, and one or two further blue stripes extending from behind the ears to the pectoral fins. The rear, around the dorsal fin, the melon and the snout, are dark blue.

The main cause of death for this species is the presence elevated levels of synthetic contaminants in the body, the polychlorinated biphenyls or PCBs. These contaminants have been used in electrical equipment, transformers, paints and sealants. They persist in the environment, bioaccumulating in the fatty tissues of marine organisms. They reach the sea via industrial discharges, sewage and stormwater runoff. This contaminant is immunosuppressive, leaving cetaceans defenceless against infections such as the Dolphin morbillivirus (DMV), highly contagious. In 1990 and 1992, it caused the deaths of thousands of dolphins in the Mediterranean. Moreover, in 1987, it wiped out 50% of the minke whale population in the North Atlantic.

Persistent Organic Compounds (PCB)

PCBs are organochlorine compounds. They comprise 209 congeners, each consisting of two benzene rings and between one and ten chlorine atoms. They are formed by the chlorination of different positions on the biphenyl molecule.

Initially, these compounds were widely marketed for their high thermal stability and resistance to flammability. As a result, their use spread in the 1950s. Subsequently, upon discovering their harmful effects on health, such as carcinogenicity and other toxic effects, they were banned from 1986 onwards.

For this reason, they have been used as lubricating oils, dielectrics, hydraulic fluids, insulating resins, paints, waxes or sealants. They can still be found in equipment and materials built before the ban, such as generators and electrical power consumers.

A study by the Zoological Society of London, together with researchers from the University of Barcelona (UB), published by Scientific Reports, warns of the high concentration of PCBs in cetaceans in European and Catalan waters.

«The study has allowed us to obtain a global picture of trends over the past 25 years. It has been observed in cetacean tissue that current PCB levels, 30 years after their ban, are excessively high in European waters, both in the Atlantic and the Mediterranean, being much higher in the latter,» according to one of the researchers., Alex Aguilar, director of the Institute for Biodiversity Research, of the University of Barcelona (IRBio-UB).

Most Affected Species

The work is based on studies of tissue samples from 1,081 cetaceans, including whales, dolphins and porpoises, and has enabled it to be established that the Orcas –Orcinus orca-, Mackerel dolphins –Tursiops truncatus– and striped dolphins –Stenella coeruleoalba– contain the highest concentrations of PCBs.

At high concentrations, they have negative effects on marine species. They are potent immunosuppressants, interfere with the reproduction and growth of animals, and cause liver and hormonal problems. In the Mediterranean and off the Catalan coast, high concentrations of PCBs were behind the deaths of thousands of dolphins in the 1990s. We still remember the slow and cruel death of a striped dolphin in '90, which swam into our arms, crying, to spend its last moments of life.

Persistent organic compounds and other marine contaminants are magnified through the trophic levels. Predators, which are higher up the food chain, are particularly susceptible to their harmful effects. Another study published in 2018 in the Journal Science, led by the scientist Jean-Pierre Desforges, demonstrates its effects on reproduction and immune function. They threaten the viability of More than 50% of the world's orca populations and, in particular, to populations near industrialised areas.

Therefore, we ask for the’expansion, to the Mediterranean Cetacean Migration Corridor, of the marine protected areas the Montgrí Natural Park, the Medes Islands, Baix Ter, the Aiguamolls and Cap de Creus, prohibiting their industrialisation.

Date of creation of the article: 20/03/2026.

WE DO NOT LET OUR GUARD DOWN

If this information has been forwarded to you and you like it, subscribe here.