In early March, a large number of starfish suddenly appeared in the waters of Qingdao Jiaozhou Bay, frantically preying on clams, oysters and other shellfish in the culture area. Although farmers are actively helping themselves, renting fishing boats and hiring divers to go to the seabed to salvage starfish, it is still difficult to make up for the losses.
According to statistics, the area affected by the disaster is about 100,000 mu, which is expected to cause economic losses of about 100 million yuan. Shellfish farmers in Jiaozhou Bay want to cry without tears. There are frequent occurrences of starfish flooding, why is it difficult to control?
This article is from WeChat official account:Liaowang Think Tank (ID: zhczyj)< span class = "text-remarks">, author: Cui Xuan He, the original title: “who” g “star? “, the title picture comes from: Visual China
“Old Jianghu” is not a vegetarian
A starfish that looks gentle, but an “old river and lake”.
The earliest starfish appeared in the late Ordovician about 450 million years ago, and experienced many mass extinctions along the way, and finally survived to this day, thanks to its unique survival rules.
Run slowly, but “stand” firmly
A starfish usually has 5 arms, but some have as many as 40 arms. There are 4 rows of dense tube feet on the underside of these wrists. The larger sea stars have thousands of tube feet.
Usually, sea stars always move slowly on their belly, with an average speed of 0.89 cm to 2.7 cm/sec. Even the fastest sand starfish is only 4.7 cm/sec. But when encountering strong winds and waves, these tube feet can keep the starfish on the ground.
The sea star uses an organ called the 罍(léi) to change the water pressure in the foot of the tube. The principle is similar to that of a hydraulic press. They drain the liquid in the tube foot into a special bag, so that the inside of the tube foot is formedA vacuum can hold objects firmly, and you are not afraid of violent storms.
Can’t hit, but it’s getting better soon
Ferocious creatures abound in the ocean. What if a small starfish encounters a predator?
They will choose strong men to break their wrists, and even when they feel the temperature rises, they will break their “arms” to cool their bodies. Under natural conditions, some kinds of starfish can completely regenerate an arm in 7 months. In other words, even if the starfish is unloaded and thrown into the sea, it can heal again, and as long as there is time, they can become multiple starfish.
Bullying the small, but never failing
The starfish has a small body. It mainly eats shellfish, crustaceans, and sometimes small fish. In short, the “old rivers and lakes” are not vegetarian at all.
Once the starfish stares at the target, it will slowly approach, and first use the tube feet to suck their shells. If the shellfish loses this power, a gap will be opened to reveal the shellfish soft body. It does not matter if the shell power is very strong. The Seastar’s Plan B is a protracted battle, holding it for a long time until the shellfish’s power is exhausted. Or death due to hypoxia.
Anyway, as long as the shell is opened by a gap, the starfish can pull the stomach from the mouth and extend it into the shell, spraying digestive juices on the prey. If the prey is relatively small, the cardia stomach can even directly wrap the prey.
Finally, the starfish will put the cardia stomach into the body and suck the prey that has become mucus.
In short, most of the shellfish that starfish stare at are unlucky.
Eat less, but can eat all the time
The digestive system of a starfish is very short, and the stomach occupies most of it, resulting in a short intestine and weak digestion and absorption capacity. According to research, the thorny sea bark can only digest 5.7% of the food, so it must continue to swallow things in order to meet the body’s needs. In addition, starfish are not only fierce but also have a habit of over-predation. They will kill ten shellfish, but may only eat one or two of them.
why does it have thisDestructive power?
The starfish that is flooding this time is the thorny sea bark, which is distributed in the Yellow Sea and the Bohai Sea, and the Qingdao coast is in this area. People in Qingdao like to “drink beer and eat clams”, and Duozhuhai Panche also likes it.
Now it is the season for clam seedlings. If the starfish cannot be completely cleaned, the date of clam seedlings will be postponed, which will greatly reduce the survival rate. When the harvest season comes, the losses to the farmers will be too great. Estimated.
The starfish, which seems harmless to humans and animals, and even a little good-looking, why are they so destructive?
First, there is more “food”.
Sea stars have the habit of gathering in food-rich areas, mainly preying on bivalves, sea urchins, oysters and sea anemones. The scale of shellfish farming in Jiaozhou Bay has been increasing year by year and has reached 20,000 hectares. The fishermen who raise shellfish artificially put in shellfish seedlings, which is equivalent to “adding a meal” to the little starfish who have just sunk to the bottom of the sea. The actual situation has also proved this. less.
The second is less “enemy”.
Sea star is not invincible in the world. Carnivorous fish such as perch, red sea bream, and small yellow croaker are all its natural enemies. But as early as the 1960s and 1970s, the number of these natural enemies dropped sharply.
In the absence of natural enemies, the survival rate of starfish larvae is increased. After the starfish enters adulthood, there are fewer natural enemies, and only seagulls and sea otters occasionally come to hunt. With climate change and man-made destruction of the marine environment, the number of these natural enemies is gradually decreasing.
The third is its own strength.
Sea stars have super reproductive ability, and individual spawns are very large, up to 2.5 million eggs at a time. In addition, it has a special function: regeneration ability.
Natural enemies are reduced, food is reduced, and reproductive ability is strong. Starfish that originally lived in the deep sea gradually moved to the shallow sea and formed a dominant species. The shellfish breeding area in the shallow sea quickly broke out in disaster.
Another main cause, ecological imbalance
This is closely related to human activities. The main cause of ecological imbalance is overfishing and neglecting the maintenance of the ecological system when breeding in the sea.
Actually, we still have a honeymoon with the starfish.
There were also sea stars in Jiaozhou Bay in the 1960s. In the age of food scarcity, fishermen followed the trail of clams and preyed on starfish, relying on their rich nutrients to survive the years of food scarcity.
Later, with the improvement of living standards, fishermen no longer eat starfish, but use them as fertilizer to improve soil quality.
In addition, starfish can also be used as biological preservatives.
At that time, the ecological environment tended to be balanced. In the sea area of about 10,000 mu, about tens of thousands of kilograms of starfish could be harvested a year. The predation of clams by starfish has not attracted people’s attention.
However, in the past 20 years, everything has begun to change. In the same area of the sea as in the past, tens of thousands of kilograms of starfish can be harvested in one month.
In 2006, Qingdao’s Huangdao waters suffered a round of coalition invasions composed of spiny seas and sea stars. Starfish eats abalone, Philippine clams, scallops and other cultured economic shellfish frantically. A starfish can eat more than a dozen scallops a day, which is amazing.
The losses of 10 abalone farmers in Houwan, Huangdao Street, which was the worst hit by the disaster, exceeded 10 million yuan, while the housing prices in this area during the same period were only 2,000 yuan/square meter to 3,000 yuan/square meter.
In April 2007, the starfish made a comeback. The density of starfish in Qingdao Jiaozhou Bay is as high as 300 per square meter, and more than 500 kilograms of starfish can be caught every day in the sea area of 3 mu to 5 mu during the peak period.
Furthermore, this year, the seawater temperature in Jiaozhou Bay is low, providing a hotbed for starfish flooding. The optimum growth temperature for sea stars is 15-20 degrees Celsius. When the water temperature is higher than 25 degrees Celsius, there are fewer sea stars.
As early as 2007, there was a large-scale flood of starfish in Jiaozhou Bay. However, as the seawater gradually warmed up, the starfish slowly receded on their own.
The affected area of Philippine clams in the Hongdao breeding area reached 60%, and the death rate of clams in some culture areas even reached 80%. A 60-horsepower fishing boat can catch more than one ton of thorny sea trays a day. Qingdao The output lost more than 100,000 tons.
This year, shellfish farmers in Jiaozhou Bay are very busy, and they can “return with a full load” after going out for five hours. One boat can salvage 4,000 to 5,000 catties of starfish a day. Buyers come to buy them every day. Because there are too many starfishes, many fishermen directly use big cranes to hoist nets of starfish ashore.
Not only in China, the spiny sea barge has been taken to the waters of Europe, North America, Tasmania and other regions with the ballast water of ships, andSuccessfully invaded and reproduced locally, causing significant losses to the local fishery, so it is listed as one of the world’s top 100 invasive alien species.
As early as 1974, Tottori Prefecture, Japan, had an outbreak of excessive spiny sea snails. The snails that were multiplied and restocked that year were almost completely eaten by spiny sea snails; 7 years later, it was in Japan again. Haipanche took pains to kill the released clams again.
In 1999, Tasmanian fishermen caught this unseen starfish from the seabed. Since then, the thorny sea pan cart has not only continued to harm the local shellfish farming industry, but also moved north along the Australian coast, causing local The sharp decrease of the endemic fish, the bold Australian scorpionfish, is due to the massive predation of starfish in the egg mass of this fish in the algae.
Will it be useful?
Seeing these news, many netizens have asked for a fight to eat starfish in Jiaozhou Bay.
Does it really work?
We have eaten a huge amount of bullfrogs and crayfish, but they still endanger Chinese water bodies as invasive species.
Furthermore, as a kind of food, starfish is not very attractive. One is that the hard “spine” and “bones” of the starfish account for a large part, and the edible part is not much; the second is that the starfish that people usually eat is actually its gonads, which contains slight toxicity. Generally, there will be some in the mouth after eating. It feels numb, it is not recommended to consume in large quantities, especially for people who are weak.
Besides, can the income from selling starfish make up for the loss?
At present, starfish that are caught ashore can still be sold, and the price of a larger one can reach 4 yuan/jin. However, the cost of labor, hiring a boat, and removing the basket has reached 3 yuan/jin. In addition, more and more sea stars are listed, and the purchase price is likely to fall further due to the influence of supply and demand.
So what better way?
In the 1970s, Japan had splashed lime to kill. Although this method can kill starfish, it is not easy to use drugs in the ocean, otherwise it will cause greater disaster.
Therefore, before there is no special means to prevent and control, people can only clean up by divers picking up starfish to reduce losses as much as possible.
Generally, each fishing boat is equipped with 1 to 4 divers, and they go out to sea at dawn. After reaching the fishing area, the divers either carry oxygen cylinders on their backs or use air pumps to dive into the seabed at 7 meters or more deep, one by one Pick up a starfish. This picking method is not efficient and has little effect.
Specifically in my country, the seawater temperature off Qingdao this year is low. It is currently impossible to predict when there will be fewer starfishes. We can only take various measures to speed up the salvage of sea stars ashore and minimize the loss to aquaculture.
So Qingdao issued a notice, “If necessary, fishermen are allowed to set up large-mesh cage nets on the seabed in the breeding area for trapping.”
The ground cage is also called the “extreme household cage”. There is only one entrance, the mesh is very small, and the inside is layered. This is mainly to use the characteristics of shrimp and shellfish like aquatic products, once you enter along the first entrance , Will keep drilling in, and eventually be swept away by a net.
Shandong’s previous “Notice on Strengthening the Management of Summer Fishing Holidays in the Ocean” required that any unit or individual is strictly prohibited from producing, selling and using nationally prohibited fishing gear and cages.
Now it is helpless to allow the use of the earth cage again.
Fundamentally speaking, the starfish disaster this time is a manifestation of the imbalance of the marine ecosystem and the result of the accumulation of many ecological crises. Therefore, only by solving the deterioration of the environment can the marine ecosystem be stabilized and the problem can be solved.
Reference material:
1. The cause of the starfish outbreak in Qingdao Jiaozhou Bay has been found! Fishing will take more than ten days! 丨Qilu Micro Newspaper, 2021-03-17
2. Preliminary study on the ecological characteristics and prevention strategies of barking behavior in spiny seas丨Master’s thesis of Ocean University of China, Li Shuyun, June 2014;
3. The Starfish Disaster丨Discovery Channel
4. Starfish invades, eats clams and scallops, netizens line up to fight! Is it possible? |Red Star News 2021-03-17
5. The sudden starfish disaster in Jiaozhou Bay, marine experts explain many questions in detail|Science and Technology Daily, 2021-03-17
6. Starfish in a big wayInvade Jiaozhou Bay! Why is it so crazy|China Environment, 2021-03-24
This article is from WeChat official account:Liaowang Think Tank (ID: zhczyj)< span class = "text-remarks">, author: Cui He Xuan