HONOLULU (CN) — The world’s smallest dolphin species is smart, playful, friendly and fewer than 50 are still alive. The Maui dolphin was listed as an endangered species Monday by the National Oceanic and Atmospheric Administration, and its cousin, the Hector’s dolphin, was listed as threatened.

An endangered species is close to extinction, while a threatened species is suffering from a massive population drop with no end in sight. While such listings can help set up designated habitats in U.S. waters, both species live in the waters of New Zealand.

The dolphins have been devastated by gillnet fishing, drowning after being caught in the fishing nets.

Gillnets are vertical nets usually set in a line. As fish swim into the net, they become trapped as the netting hooks itself behind the gills. Dolphins breathe air.

The United Nations passed a resolution in 1991 banning large-scale use of gillnets in international waters. Some U.S. states have banned or heavily regulated gillnets.

The Monday announcement by NOAA means the U.S. government will prohibit commercial sale, importing and exporting of the Maui dolphin.

The New Zealand government has enacted laws protecting the dolphins, but less than half their habitat is covered. According to the World Wildlife Fund, the Maui dolphin will go extinct within a few decades unless more is done to protect them.

The population of the Hector’s dolphins has dropped by 80 percent in the past 50 years, from an estimated 50,000 in 1970 to about 9,000 today.

Maui dolphins dropped from 1,500 to less than 50.

In addition to dangers from the fishing industry, Maui dolphins have a low birth rate and are unable to breed in high numbers. In their 20-year life span, females take seven to nine years to mature and give birth to one just calf every two to four years.

Mining and oil drilling also threaten the dolphins’ habitat, as drilling disrupts the seabed where dolphins hunt for food.

In 2008, New Zealand set up a marine mammal sanctuary and restricted gillnet fishing where the dolphins are known to live. Despite increasing the sanctuary’s size to about 3,800 square miles in 2013, some say it’s not enough to save the dolphins from extinction.

In June this year, the Scientific Committee of the International Whaling Commission urged New Zealand to expand the area of prohibited net fishing, noting that no other actions have been taken to save the dolphins in the past four years.

“It therefore concludes, as it has repeatedly in the past, that existing management measures in relation to bycatch mitigation fall short of what has been recommended previously and expresses continued grave concern over the status of this small, severely depleted subspecies,” the committee wrote.

The baiji dolphin, also called the river dolphin, was declared in 2006 to be the first dolphin species to become extinct in modern times.