Animal activists have been angered by Marineland's plans to transfer its two killer whales to Japan, a move France's ecology minister said she opposed over Tokyo's more lax animal welfare laws.

Marineland was hit by a firestorm of controversy in March after two of its orcas died within five months of each other.

The park, near Antibes on the French Riviera, has some 4,000 animals from 150 different species. But visitor numbers have dropped from 1.2 million a year to just 425,000 over the last decade.

The November 2021 law "banning cetacean shows means that Marineland will have to envisage this closure" in January 2025, said the park, adding 90 percent of its visitors come for its orca and dolphin performances.

Marineland has until December 2026 to part with its two remaining killer whales, Keijo and Wikie.

The priority is to "relocate all of the animals to the best facilities currently available", the park added.

But the planned move of its last two orcas -- both born in captivity -- to Japan is unacceptable, France's Ecology Minister Agnes Pannier-Runacher told Franceinfo radio last month.

"In Japan, there is not extensive regulation concerning animal welfare," she argued.