Scientists in desperate race to save Croatian clam from extinction

The noble pen shell, one of the Mediterranean's largest and most recognizable shellfish species, is on the brink of extinction. 

Scientists estimate that more than 99 percent of its population has disappeared since a mass mortality event began several years ago. Along Croatia's Adriatic coast, researchers are racing to save one of the sea's most endangered inhabitants.

Underwater surveys along the Istrian coast have revealed only a handful of surviving specimens. The species, once widespread across the Adriatic Sea, has become exceptionally rare.

'Small numbers'

"There used to be a lot of them, but now there are only two left. Here, the locals say maybe three, but these are all small numbers. In the whole of Istria, we currently have four or five that we know are alive. In the whole of Croatia, we do not even have ten of them," said Sandro Dujmovic, Director of Natura Histrica.

Scientists say the collapse of noble pen shell populations was triggered by a deadly parasite and compounded by rising sea temperatures. Together, these factors devastated populations across the Mediterranean.

Some experts also point to human activities as an additional cause of the species' decline. According to researchers, the expansion of marinas and coastal land reclamation projects has destroyed parts of the noble pen shell's natural habitat.

'Alarming situation'

"It's an alarming situation. And it doesn't just happen with noble pen shells. Now you have the extinction in many burrows, because of the rising sea temperatures, and probably some other factors. 

"Many marine life they are growing, is dying," said Milvana Arko Pijevac, a marine ecosystems expert.

At Aquarium Pula, several surviving noble pen shells are being kept in protected conditions. Researchers feed them with laboratory-grown phytoplankton and hope they may eventually reproduce.

Similar conservation programs are underway in Spain, Italy and other Mediterranean countries. Despite years of effort, scientists have yet to achieve a breakthrough.

"Unfortunately, since 2016 - Spain started, and even our group and the Italian group -we haven't succeeded yet. 

"We don't know anything about reproduction yet, except that we're going to keep trying. This is the only way we're going to succeed," said Milena Micic, President and CEO of Aquarium Pula.

Scientists warn that the rapid disappearance of the noble pen shell may be an early indication of broader changes affecting marine ecosystems across the Mediterranean and beyond.