Around the world, pollution has been linked with a rise in male fish with feminine features. To see if the problem had spread along the coast of Northern Spain, a group of researchers with UPV/EHU's Cell Biology in Environmental Toxicology program began collecting specimens of thick-lipped grey mullet.
In all six estuary regions where the biologists collected fish, they found examples of feminized male species and even intersex fish, specimens with featured testicles containing eggs.
"Endocrine disruption is a phenomenon that has spread all over our estuaries, which means that, as has been detected in other countries, we have a problem with pollutants," said Miren P. Cajaraville, who led the research effort.
Like elsewhere, the sexually-confused fish have been blamed on pollutants -- specifically a group of endocrine-disrupting chemicals, which vary widely in actual chemical makeup, but which all have the same interfering effect on animal hormones. These chemicals can be found in everyday products: pesticides, contraceptive pills, detergents, cosmetics and more -- all of which easily seep into the water system.
In testing the bile of collected mullet specimens, the biologists showed that these endocrine-disrupting pollutants were present in all the ecosystems where the feminized fish were found.
"We have confirmed the correlation existing between the presence of the pollutants and the feminization phenomenon," said Cajaraville.
The details of the study were recently published in both the journal of Science of the Total Environment and the journal of Marine Environmental Research.