Tokyo police have arrested five people in relation to the suspected illegal breeding and sales of genetically modified fluorescent killifish, or medaka.
The suspects include Masuda Tomio, the owner of a killifish shop in Kasukabe City, Saitama Prefecture, north of Tokyo.
The police say the five people are suspected of illegally breeding and selling the genetically engineered fish from 2021 through last year.
Transactions involving living modified organisms are restricted under a law based on an international agreement called the Cartagena Protocol on Biosafety. The law is aimed at preventing adverse effects on biological diversity and the environment.
The police say the killifish in question came from a university laboratory. Researchers there had developed genetically modified fluorescent killifish for use in research.
A graduate student at the lab took about 30 killifish eggs out of the facility from 2009 through 2010. The fluorescent killifish has become popular among fish enthusiasts and were sold repeatedly.
The police say about 50 people had been in possession of such killifish, including the five who were arrested, and that about 1,400 fish were confiscated in the latest search.
They say all of the suspects have admitted to the charges. No negative effects have been confirmed on the ecosystem. The police have called on the public to be careful of such illegal sales.