It invades fishing grounds on a large scale and preys on shellfish. What is this "killer"?

Review expert: Ancient Mingdi Lian (He Lin)

Zhihu famous science blogger on mollusks

Do you remember the sudden "invasion" of Jiaozhou Bay by starfish last March? Under the aggressive invasion of starfish, the fishermen in Jiaozhou Bay suffered heavy losses in the clams and oysters they raised near the coast. According to incomplete statistics, more than 100,000 mu of oyster breeding areas were invaded by starfish, with a density of more than 50 starfish per square meter, causing losses of over 100 million yuan.

But fortunately, after relevant media released the news that Jiaozhou Bay was invaded by starfish, from March 14 to March 17, 2021, buyers from all over the country gathered in Jiaozhou Bay to purchase starfish. The hot sales of starfish reduced the losses of fishermen.

As soon as one crisis is over, another crisis arises. Just when we dealt with Patrick Star, here comes another freeloader: the white mud ant . When this thing first appeared, it did not attract people's attention. After it became rampant, it was found that it was more harmful to oysters and other shellfish than starfish.

White mud ant (long yellow-white creature in the middle of the hand) Source｜Zhangwen Video

The fishermen said: "It's so hard for me!" They were just hit by the influx of starfish, and just when they recovered a little blood, another white mud ant came and hit them again.

So, who exactly are the white mud ants that make the fishermen exhausted, and what kind of bloody storm has it brought?

What is the white mud ant?

The official name of the white mud ant is Philine kinglipini, which belongs to the Philine family and Philine genus (also known as the Philine snail genus). It looks similar to a slug, but has a thin shell. The white mud ant grows quickly and has a well-developed radula in its mouth, which makes it easier for them to prey on larvae of shellfish such as clams.

Source: Entry on the Chrysostomidae

White mud ants are usually distributed in the Sea of ​​Japan, and also in small quantities in coastal areas of my country such as the Bohai Sea, the East China Sea, and the Yellow Sea. Their larvae follow the tide to the coastal shellfish seedling production areas or nursery ponds in March every year, where they settle and grow, and may cause an outbreak when the environment is suitable.

Why do white mud ants appear on such a large scale?

1. Expansion of the aquaculture industry

As the market size expands, the scale of shellfish farming is also increasing. The expansion of shellfish farming is bound to cause an outbreak of species such as starfish, which are natural enemies of shellfish. However, creatures in the ocean generally only prey on young starfish, and adult starfish have almost no natural enemies. **With plenty of food and a lack of natural enemies, it is not surprising that starfish are exploding. **Starfish prey on other mollusks in large numbers, but because white mud ants are hidden deep in the sand and mud, few starfish can prey on them. Without other mollusks with similar habitats as competitors, the proliferation of white mud ants is easy to imagine.

2. Impact of human activities

Humans have been fishing marine life on a large scale, which has greatly reduced the number of fish that prey on larval starfish and white mud ants, such as their natural enemies, red sea bream and goby. At the same time, some starfish may be attached to human ships or carried to other sea areas in ballast water, and white mud ants also take a ride.

What harm does white mud ants do?

You may have heard of mud ants. "Mud ants" is the local common name for mud snails (Bullacta exarata). Mud snails are a seafood product with delicious meat and can be eaten. However, white mud ants are not only inedible, but the mucus they secrete can also cause human allergies, so they cannot be eaten.

Source of Drunken Mud Snails: A shopping website

Compared to the starfish that has troubled fishermen for a long time, people know very little about the "white mud ants" that have only recently erupted on a large scale. What is known so far is that white mud ants are omnivorous species that eat small invertebrates in mud and sand. They like to eat bivalves and excrete two empty shells, so fishermen in Qingdao call it "one and a half". After the large-scale outbreak, white mud ants feed on shellfish such as clams in large quantities. Fishermen in Jiaozhou Bay have lost millions of yuan due to the rampant white mud ants.

Source｜Poster Video

In addition, the natural enemies of white mud ants in the local ecological environment, such as red sea bream and goby, have decreased due to human fishing . When the number of white mud ants increases explosively, it will seriously occupy the limited living space and resources of other species, causing the number of other organisms to decline sharply, seriously endangering the stability of the local ecosystem. Therefore, it is urgent to solve the problem of the rampant white mud ants.

How to deal with white mud ants?

People will experience allergic reactions after eating white mud ants, so thinking of solving the problem by eating will not work.

White mud ants live in burrows in the mud and sand on the seabed, so ordinary fishing methods are ineffective. The more useful tools are ground trap nets and bottom trawl nets. However, according to relevant regulations, these tools are prohibited under normal circumstances because trawl nets can seriously damage the seabed ecology.

After continuous attention and follow-up investigation, the relevant departments decided to allow fishermen to temporarily use ground trap nets and bottom trawl nets, but only for the removal of starfish and white mud ants. A few days after the policy was opened, fishermen began the cleanup work, catching starfish and white mud ants at sea, and one boat could salvage more than 500 tons at a time. After several days of deep cleaning, the number of white mud ants dropped sharply.

Source: CCTV Video

Since the salvaged white mud ants have little value, they are usually dried in the sun. After drying, they are usually destroyed by landfill incineration or other methods, or they can be used as feed.

Source: Xue Dayuan, ed. Current status and protection of China's biological genetic resources[M]. 2005

Using bottom trawls and ground traps to deal with the rampant white mud ants and starfish is ultimately just a stopgap measure. Because during the fishing process, ground traps and bottom trawls will catch all sizes of marine life, and other marine life will also be caught. Long-term use will inevitably damage the marine ecological environment.

In order to completely solve the problem of the proliferation of starfish and white mud ants, it is necessary to conduct systematic investigations and studies to analyze their living habits and outbreak processes, so as to develop early warning mechanisms and protect the ecological balance.