VOA科学技术2023--人类、海豚一起捕鱼

Humans, Dolphins Working Together to Fish

A fishing community in southern Brazil has an unusual ally: wild dolphins.

Stories of people and dolphins working together to catch fish go back thousands of years.

But historians and storytellers have told the human side of the story. Until recently, it has been impossible to know how dolphins have benefited from the relationship. Now, sonar and underwater listening devices can follow them underwater and suggest an answer.

In the coastal¹ city of Laguna, scientists have used drones, underwater sound recordings² and other tools to track dolphins. The scientists can see how local people and dolphins cooperate and benefit from each other's work. The most successful humans and dolphins are skilled at reading each other's body language.

The research was published Monday in the journal Proceedings³ of the National Academy of Sciences.

The Laguna residents work with wild bottlenose dolphins to catch schools, or groups, of silver fish called mullet. It is an alliance that has been recorded in local newspaper records going back 150 years.

"This study clearly shows that both dolphins and humans are paying attention to each other's behavior, and that dolphins provide a cue to when the nets should be cast," said Stephanie King. She is a biologist who studies dolphin communication at the University of Bristol in Britain and was not involved in the research.

"By working with the dolphins," the people catch more fish, "and the dolphins are more successful in foraging⁴, too," King added.

When it comes to fishing, dolphins and humans have different abilities.

Mauricio Cantor is an Oregon State University marine⁵ biologist and co-writer of the study. In Laguna, the water is cloudy, so people are unable to see the fish, he said. But the dolphins use sounds to find them. As the dolphins herd⁶ the fish toward the coast, the people run into the water holding fish nets.

"They wait for dolphins to signal exactly where fish are – the most common signal is what locals call ‘a jump,' or a sudden deep dive," Cantor said.

The researchers used sonar and underwater listening devices, or microphones, to track the positions of the dolphins and fish. Drones recorded the action from above, and GPS devices attached to residents' wrists recorded when they casted their nets.

The more closely the people timed casting their net to the dolphins' signals, the more likely they were to catch a large amount of fish.

How do dolphins benefit?

When the nets fall in the water, it scares the fish. They then break into smaller schools that are easier for dolphins to hunt. Cantor said the dolphins sometimes also take one or two fish from the net.

The Laguna residents group the individual dolphins as "good," "bad," or "lazy." The grouping is based on their skill in hunting and likelihood of cooperating with humans, said Cantor. The people get most excited when they see a "good" dolphin approaching shore.

It is not clear how the Laguna cooperation first started. But it has survived many human and dolphin generations. The knowledge is passed down by experienced fishers and dolphins to the next generation of both.

Still, the researchers in Brazil worry that the Laguna alliance may be in danger. Pollution threatens the dolphins and there are fewer local fisheries.

Scientists hope that more attention to the unusual cooperation can help drive support to protect it.

Words in This Story

benefit — n. to gain a good result from some activity or relationship

sonar (sound navigation and ranging) — n. a device that uses sound to find things underwater

resident — n. a person who lives in a particular place for some time

cue — n. to give a signal to start something

cast — v. to throw a line or a net into the water to catch fish or other animals

forage⁷ — v. to look for food or supplies

herd — v. a group of certain kinds of animals such as cattle, sheep, goats and whales

wrist –n. the joint⁸ between the hand and the arm

lazy — adj. not liking or unwilling to do hard work

1 coastal   

adj.海岸的，沿海的，沿岸的

参考例句：

• The ocean waves are slowly eating away the coastal rocks.大海的波浪慢慢地侵蚀着岸边的岩石。
• This country will fortify the coastal areas.该国将加强沿海地区的防御。

2 recordings   

n.记录( recording的名词复数 )；录音；录像；唱片

参考例句：

• a boxed set of original recordings 一套盒装原声录音带
• old jazz recordings reissued on CD 以激光唱片重新发行的老爵士乐

3 proceedings   

n.进程，过程，议程；诉讼(程序)；公报

参考例句：

• He was released on bail pending committal proceedings. 他交保获释正在候审。
• to initiate legal proceedings against sb 对某人提起诉讼

4 foraging   

v.搜寻（食物），尤指动物觅（食）( forage的现在分词 )；（尤指用手）搜寻（东西）

参考例句：

• They eke out a precarious existence foraging in rubbish dumps. 他们靠在垃圾场捡垃圾维持着朝不保夕的生活。 来自《简明英汉词典》
• The campers went foraging for wood to make a fire. 露营者去搜寻柴木点火。 来自辞典例句

5 marine   

adj.海的；海生的；航海的；海事的；n.水兵

参考例句：

• Marine creatures are those which live in the sea. 海洋生物是生存在海里的生物。
• When the war broke out,he volunteered for the Marine Corps.战争爆发时，他自愿参加了海军陆战队。

6 herd   

n.兽群，牧群；vt.使集中，把…赶在一起

参考例句：

• She drove the herd of cattle through the wilderness.她赶着牛群穿过荒野。
• He had no opinions of his own but simply follow the herd.他从无主见，只是人云亦云。

7 forage   

n.(牛马的)饲料，粮草；v.搜寻，翻寻

参考例句：

• They were forced to forage for clothing and fuel.他们不得不去寻找衣服和燃料。
• Now the nutritive value of the forage is reduced.此时牧草的营养价值也下降了。

8 joint   

adj.联合的，共同的；n.关节，接合处；v.连接，贴合

参考例句：

• I had a bad fall,which put my shoulder out of joint.我重重地摔了一跤，肩膀脫臼了。
• We wrote a letter in joint names.我们联名写了封信。