Overfishing in international waters has surged in the past five years and demonstrates the need to ratify a recent global treaty to protect the high seas, a Greenpeace report said Wednesday.

The non-governmental network is calling on as many countries as possible to sign the treaty next week at the United Nations General Assembly in New York.

Finalized in June, the text was hailed as a "historic" accord with the potential to better safeguard the oceans.

A key element in the treaty is the creation of a legal framework to protect high seas marine areas — beyond 230 miles (370 kilometers) from coastlines — whose good health is vital to humanity.

But without enforcement of the accord, such protections are minimal, the report warned.

"Reality at sea is moving in the opposite direction from the ambition laid out in the Treaty," it said.

Governments must step up immediately, urged Greenpeace oceans campaigner Chris Thorne, aboard the group's ship Arctic Sunrise, which was docked Wednesday in Long Beach, California for an event marking the report's release.

To protect 30 percent of Earth's land and oceans by 2030, the target adopted last year by the COP15 convention on biological diversity, "there is no time to waste," he told AFP.

Fishing hours on the high seas increased by 8.5 percent between 2018 and 2022, according to the report, which compiles data from an organization capable of tracking boat movements via their transmitters.

Such intensification is especially pronounced in the ecologically sensitive areas identified by the UN as potential future marine sanctuaries. Greenpeace reported fishing there has increased by 22.5 percent over the same period.

"Overfishing is a huge problem," Thorne said.

"That fishing pressure is just absolutely unsustainable, and it's pushing our oceans to the brink."