Recently scientists have announced some good news: Several important tuna (金枪鱼) species have stepped back from the edge of extinction.

Two bluefin tuna species, a yellowfin, and an albacore are no. longer seriously endangered or have moved off the leading international list of endangered species entirely.

The unexpectedly fast recovery speaks to the success of efforts over the past decade to end overfishing. But tuna are not the only species scientists are thinking carefully at the 2021 World Conservation Congress in Marseille, France, which is organized by the International Union for Conservation of Nature (IUCN). Researchers warn that many other sea species continued to be imperiled. For example, more than a third of the world’s sharks are still threatened with extinction due to overfishing, habitat loss, and climate change.

“I think the good news is that sustainable (可持续的) fishing industry is possible,” says Beth Polidoro, a biologist at Arizona State University. “We can eat fish without reducing the population to the point where it is on the road to dying out or extinction.” At the same time, she warns that the recovery should not encourage us to catch as many fish as we want. “We need to keep doing what’s working.” Polidoro adds.

The IUCN, which determines the world’s most endangered species on its Red List of Threatened Species, also announced at the meeting that some animals are moving in the other direction, onto the Red List. Like the Komodo dragon, an lizard (蜥蜴), it is at particular risk from climate change.

Of course, the work of protection is never over, and it will require close and continuous attention to make sure neither tuna nor Komodo dragons return to the edge of dying out. But for now, people can celebrate a few wins for the animal world.

Many people just see crows (乌鸦) as a natural clean-up crew—eating insects, dead animals or food in trash cans. But researchers have found that crows are not only playful but also social and intelligent. They use tools to solve problems, and they remember faces for years and copy sounds they hear.

“Crows are always testing their environment,” said John Marzluff, University of Washington professor of wildlife science. “Anything that looks possibly edible, they will taste it.” This trait (特点) has led to interesting scientific findings. Some crows use sticks to gain hard-to-get treats. In other experiments, they learned to drop stones into narrow containers to raise water to a level where they can drink it or reach a floating treat inside.

Crows are social, living in large extended families of more than a dozen birds. Communication is key to their survival. Many calls are used—each having a different message. For example, they have separate warning calls for cats, dogs and people. Some crows even imitate the sounds of other animals and people.

Marzluff did several experiments to determine whether wild crows remember human faces. In one, researchers wearing masks caught seven crows around the campus and banded them. After setting them free, researchers found that regular passers-by got no reaction, but as soon as anyone wearing the same mask passed by, the crows made loud warning calls—even years later. Never be mean to a crow. They not only remember faces but teach their offspring who to beware of (当心). They also remember those who were kind to them and pass that information along, too, often bringing gifts of rocks or other small objects as a thank-you.

Far from the land of Antarctica（南极洲）, a huge shelf of ice meets the ocean. At the underside of the shelf there lives a small fish, the Antarctic cod.

For forty years scientists have been curious about that fish. How does it live where most fish would freeze to death? It must have some secrets. The Antarctic is not a comfortable place to work and research has been slow. Now it seems we have an answer.

Research was begun by cutting holes in the ice and catching the fish. Scientists studied the fish's blood and measured its freezing point.

The fish were taken from seawater that had a temperature of—1.88°C and many tiny pieces of ice floating in it. The blood of the fish did not begin to freeze until its temperature was lowered to-2.05°C. That small difference is enough for the fish to live at the freezing temperature of the ice—salt mixture.

The scientists' next research job was clear： Find out what in the fish's blood kept it from freezing. Their research led to some really strange thing made up of a protein（蛋白质）that has never been seen before in the blood of a fish. When it was removed, the blood froze at seawater temperature. When it was put back, the blood again had its antifreeze quality and a lowered freezing point.

Study showed that it is an unusual kind of protein. It has many small sugar molecules（分子）held in special positions within each big protein molecule. Because of its sugar content, it is called a glycoprotein. So it has come to be called the antifreeze fish glycoprotein, or AFGP.