Discovery Near Sesoko Island
A plastic bottle made from high-density polyethylene and manufactured in China was found floating near Sesoko Island in Okinawa. Inside was a three-spot swimming crab, Portunus sanguinolentus. The crab had entered the bottle as a larva, grew too large to escape, and survived by feeding on small fish and algae that developed inside the container.
On July 7, the bottle was spotted about 500 meters from Sesoko Island. It was floating without a cap. The bottle had been produced roughly eight months before it was found. Its opening was just 24 millimeters wide, but the crab measured 88.23 millimeters across—making it more than three times wider than the neck. Weighing 42.06 grams, the crab was so large that researchers had to cut the plastic to free it.
Research and Findings
The age of the bottle was confirmed by barnacles attached to its surface. It had been drifting for at least 62 days. DNA analysis showed the crab had eaten juvenile fish, including triggerfish and sergeant majors, as well as green and brown algae growing on the bottle’s inner walls. The female crab had also begun developing ovaries.
Researchers Hajime Sato and Yoichi Sakai noted: 'To our surprise, a large live swimming crab, Portunus sanguinolentus, was caught inside the bottle. The crab was clearly larger than the bottle opening!'
They also emphasized that 'plastic bottles discarded by humans can trap crabs and prevent their escape.' Similar incidents have been recorded in waters around Japan, suggesting this is not an isolated event, according to the researchers in a release from Hiroshima University.
This discovery off Okinawa highlights the serious issue of ocean plastic pollution and its impact on marine life. It serves as another reminder of how human activity can disrupt ecosystems, endanger marine species, and hinder their survival. Continued research and discussion on the effects of plastic waste are essential to finding effective solutions for reducing ocean pollution.