My Deep-sea Fishery

Advanced detection equipment does not work on jellyfish. Therefore, the investigation process of jellyfish by Chinese researchers is also difficult and tortuous.

Researchers can only take boats and go to sea every two months to study jellyfish with primitive methods such as naked eye observation and fishing nets.

It was in 2011 that Chinese researchers made significant achievements in the study of jellyfish.

On July 21, 2011, researchers set sail to investigate Jiaozhou Bay.

Jiaozhou Bay is located in the southern part of the Shandong Peninsula. It is a fan-shaped bay with an area of ​​390 square kilometers. During that expedition, researchers cast fishing nets at three points in Jiaozhou Bay.

After putting in the fishing nets, the scientific research boat moved forward, and every minute it traveled, four or five jellyfish quietly appeared beside the boat, including the rosy jellyfish and the giant sand jellyfish.

But whenever people use a simple fishing net to fish, the jellyfish often slip away before the net gets close.

Although jellyfish do not have brains, their most sensitive sensory organs are distributed on the edge of each jellyfish fan. These sensory organs have both the functions of ears and eyes. Infrasound, feeling the threat approaching, fled early.

After three hours of hard work, the researchers pulled up two fishing nets successively, but the results were not satisfactory. All the nets caught were sporadic jellyfish.

Scientists are very strange.

It was the fish-rest period at that time, and it stands to reason that it was the time when there were the most fish in the ocean, but it happened that not a single live fish could be caught.

Later, after investigation, the researchers discovered that there were too many jellyfish in that sea area, which had eaten all the eggs of the local fish, and the sea fish had faults.

As for why there are so many jellyfish in that sea area, the explanation of the researchers is that, firstly, the overfishing of fish by humans has saved the jellyfish larvae, which were originally the food of fish, to survive in large numbers and grow into adults.

The second is that with the reduction of fish in Jiaozhou Bay, there are fewer natural enemies that compete with jellyfish for food, providing opportunities for jellyfish outbreaks.

When the third net was recovered, the researchers found the jellyfish and six large jelly-like objects still in the net.

The local fishermen said that they have not seen such a large jellyfish in the coastal waters for decades, which is surprising.

Ten years ago, large-scale fishery research ships were operating in the Yellow Sea and the East China Sea, and all they caught were marine fish, and jellyfish were rarely seen.

That survey found that among the jellyfish outbreaks in my country, the three most common types of jellyfish are moon jellyfish, sand jellyfish, and rosy jellyfish.

"Brother Yang, are you sure these jellyfish are edible? I heard that they are dangerous." Fang Youqun lay on the side of the boat, saying danger in his mouth, but in fact there was no trace of fear in his eyes. This seemingly weak, but actually terrifying creature has no sense of fear at all.

"The danger is real. Jellyfish are one of the most ferocious carnivores in the world and one of the most poisonous creatures in nature, but it is also true that they can be eaten. Now in many restaurants around the world, there are special dishes The chef of jellyfish or jellyfish." Xiang Yang said with a smile.

"The outbreak of jellyfish is caused by the reduction of natural enemies of jellyfish due to overfishing. However, from a global perspective, some areas are not overfished. It's really strange to see the signs of jellyfish outbreak." Xia Pengjie thought on the side.

"I don't know about that. I have to ask those scientists who specialize in jellyfish." Xiang Yang said with a smile.

In fact, it is difficult for scientists to answer this difficult question.

With the continuous outbreak of jellyfish in recent years, many scientific research institutions and maritime universities have begun to pay attention to jellyfish.

In Xiang Yang's alma mater, there is a special major related to jellyfish.

In order to find out what factors other than overfishing have caused the jellyfish outbreak, the scientists also established a laboratory that can control and simulate the marine environment, and selected the most widely distributed jellyfish in the world's oceans, the moon jellyfish, as the first batch of samples Feed and observe.

The water moon jellyfish has four ring-shaped stomachs, and the place corresponding to the stomach under the umbrella is the gonad.

Usually, a pair of male jellyfish and female jellyfish can discharge 100,000 sperm and eggs. After fertilization in water, the fertilized eggs sink to the bottom of the sea, find hard things to attach to, and develop into polyps.

The polyps are only two millimeters in size and are the larvae of the jellyfish.

But the scientists discovered under the microscope that the polyp has a very strong predation ability, and can even directly grab an Artemia into its mouth.

According to relevant surveys, as long as polyps appear in a sea area, more than half of the zooplankton in the entire water area will be consumed by polyps.

The appearance of polyps greatly reduces the bait for fish and has a great impact on the overall ecological balance of the ocean.

"The most annoying thing about jellyfish is that it has no brain, doesn't know how hungry it is, and eats all its life. These foods are usually mainly plankton, supplemented by small fish and shrimp, and sometimes even prey on the same kind. If you let it The flood of jellyfish is absolutely devastating to the fishing industry," Xia Pengjie said.

Xiang Yang nodded, "That's right, so since we have encountered these stinging jellyfish, we have to find a way to salvage some of them even if it is thankless, not to mention that these stinging jellyfish are still edible, and they are expensive. "

Xiang Yang once saw the stinging jellyfish preying on the moon jellyfish in the laboratory.

The usually beautiful and gentle stinging jellyfish is like a white-haired witch when eating. Its most powerful weapon is its tentacles. When it catches its prey, hundreds of stinging cells in each tentacles will quickly penetrate the opponent's flesh and then release them immediately. The venom paralyzes the prey in just a split second, making the prey completely unconscious and at the mercy of the stinging jellyfish.

Xiang Yang has seen the ferocious side of the seemingly gentle jellyfish with his own eyes, so Xiang Yang dare not underestimate these jellyfish at all.

Xiang Yang looked around at the crew members who were already wearing protective clothing and said: "When jellyfish feed, they will first stab their prey to death with their cnidocytes. Some of them will be eaten, and more will sink to the bottom of the sea and be wasted. When you salvage jellyfish, you must not take off your protective clothing, understand?"

"Don't worry, Brother Yang, we promise not to let jellyfish touch our skin." Fang Youqun said nonchalantly.

Xiang Yang frowned, and said: "I'm not talking about keeping you from touching the stinging jellyfish, but during the whole salvage process, you are not allowed to take off the protective clothing. The longest tentacles of the stinging jellyfish can grow up to 50 meters, so its The lethality is still strong at a distance of 50 meters, as long as you don't wear protective clothing, no matter how careful you are, you will definitely get hit."