Scientists at the Royal Burgers Zoo, in Arnhem, Netherlands, have become the first to successfully give a fish contraception after they gave a female spotted eagle ray the implant in a bid to prevent overpopulation, as they found two of the dominant cartilaginous fish, risked taking over Europe.
By separating the pair by moving one to another aquarium, they were able to insert the birth control into her left pectoral fin.
A spokesperson for Royal Burgers Zoo said: "This breakthrough has far-reaching consequences for the European breeding programmes of various fish species.
"With this extra method of population management, the programmes can be managed in an even more targeted way."
Scientists had tried twice before to carry out the successful application on a ray - but were unsuccessful.