Professor Ma from the Yellow Sea Fisheries Research Institute of the Chinese Academy of Fishery Sciences said that yellow croaker looks very similar to tridentate fish and white croaker, and it is mainly identified by the color of scales, the position of mouth and the shape of swimming tube. Except that the belly scales of yellow croaker are golden yellow and the mouth is in the middle, the swimming tube of white croaker is divided into two, while the swimming tube of white croaker is divided into many parts, with lower mouth and white scales.

Director Wang of Shenyang Aquatic Technology Extension Station told the reporter that the dyed white-flowered fish wiped the fish with white toilet paper, and the paper generally left obvious yellow. And frozen into a big lump (block) of dyed white fish, some ice will also appear yellow. The large yellow croaker may be soaked in water for about 5 minutes, and the water may turn into beer color.

The second category: "Dalian Dao" is basically extinct.

In fact, as early as last year, this newspaper reported on the topic "There are no more Dalian knives in the world". Because of overfishing and other problems, it is difficult to see swordfish fishing in the Bohai Sea where Dalian is located. On June 24th, 65438, when the reporter came to the seafood wholesale market in Dadong District again, he saw that many vendors there were still selling swordfish under the banner of "Dalian Swordfish". Especially those swordfish marked with the words "Dalian Wild Swordfish", the price per kilogram actually reached about 120 yuan. In this regard, the reporter contacted Zhou Xiong, who is still engaged in fishing in Dalian Bay. He told reporters: "In fact, most of the swordfish sold on the market now are swordfish caught in Zhoushan Fishing Ground in autumn and then refrigerated, and it is absolutely impossible to be Dalian swordfish. I have been fishing for so many years, can I wonder if there are swordfish in Dalian waters? "

Subsequently, the reporter contacted Wang Wei, an associate professor in the Department of Life Sciences of Dalian Fisheries College. He said: "Because of overfishing and other reasons, it is difficult to see saury in the Bohai Sea, let alone catch it in large quantities during the fishing ban."

Regarding how to distinguish Dalian swordfish, Wang Wei said that the width of swordfish in Dalian, Zhoushan and other places is generally only 4 to 7 cm, and the length will not exceed 60 cm. Then the tail of saury in Dalian is very thin, like a thread, so it is sometimes called "thread belt", while the tail of saury imported from India and other countries is usually short and thick.

The third category: oil fish posing as cod is easy to cause diarrhea.

After eating a catty of 10 yuan cod bought from the market, Ms. Liu and her son developed diarrhea in different degrees at the same time. Accordingly, Ms. Liu suspected that it was because she didn't buy cod.

Ms. Liu told the reporter that afterwards, she learned through online inquiry that the real price of cod was usually more than RMB 0/00 per catty, while the price of "cod" she bought was only RMB 0/kloc-0 per catty/0 yuan. This so-called "cod" is not a real cod, but an oily fish that looks like cod. Li Lujing, a researcher at the Aquatic Technology Extension Station of Shandong Provincial Department of Ocean and Fisheries, said in an interview with relevant media that the real price of cod should be at least above 80 yuan per catty, or even 100 yuan. If you bought 10 in the supermarket, you can conclude that it is oily fish rather than cod.

Moreover, oil fish has high fat content and high melting point, and it is not easy to dissolve in the body, which will lead to diarrhea in different degrees. "In Europe, oily fish are classified as toxic fish species and are prohibited from being listed."

As for the difference between the two, Li Lujing said that oily fish usually have a flat and slender body, a big mouth, big eyes and small and rough scales. As for how consumers can avoid being fooled, the first thing to look at is the price. A catty of cod fillets with a market price of 10 yuan can't be real cod.

The fourth category: Left-mouthed fish pass off as precious fish.

Ms. Xing, who lives in Fangjialan, Shenhe District, told the reporter that she originally planned to cook steamed turbot for her family during New Year's Day. But in the farmer's market near her home, she found that the price of Duobao fish sold by almost all merchants was around 40 yuan per catty, except one merchant. "At that time, she told me that her family's Duobao fish was only 30 yuan per catty. I thought it was very cheap and bought it." However, that night, when Ms. Xing's lover was tasting steamed turbot, she suddenly said to her, "No, that's not what I used to eat in a restaurant." Later, after a friend's appraisal, what Ms. Xing bought was not a treasure fish, but an authentic left-handed fish.

Wang Wei, an associate professor in the Department of Life Sciences of Dalian Fisheries College, told the reporter that Duobao fish, also known as butterfly fish, is a kind of fish with a partial mouth and a very popular fish in the fish market. Wang Wei said that it was quite common for left-handed fish to pass off as treasure fish in the past. "Now this kind of situation is not very common, but there are still people pretending to be treasure fish with left-handed fish. After all, the price of real treasure fish is still maintained at forty or fifty yuan per catty. "

Wei Wang said, the first thing to distinguish between the two is the appearance. "From the side, the left-handed fish looks flat, a little oval, and the Duobao fish is flat and almost round. Then the color of Duobao fish will be lighter than that of left-handed fish, and Duobao fish will be lighter. In addition, the meat quality of Duobao fish is more delicate, tender and delicious, while the meat quality of left-handed fish is thicker. "

The fifth category: Yangtze river swordfish has a minimum of 3,000 to 4,000 yuan per catty.

Ms. Liu, who lives in Shenhe District, found that the Yangtze River saury appeared in the morning market near her home recently, and the price was only 20 yuan money per catty. This aroused Ms. Liu's curiosity. "I heard that there are high-end restaurants in Shenyang that once sold Yangtze saury, and the price of the dishes made should reach more than 10,000 yuan. Now, how can this precious fish appear in the ordinary farmer's market, and the price is still so low? "

Later, the reporter also came to the morning market along the river, where she really saw what Ms. Liu called the Yangtze River saury. The reporter saw that this saury is long and flat, and it is indeed a bit like a "sharp knife". The fishmonger told reporters that this is a genuine Yangtze saury. At this time, the fishmonger also took out three or four swordfish from the foam box. "Would you like some? 20 yuan a catty, not expensive at all. " However, a vendor selling shad sneered at this. "Do you really think these are Yangtze saury? Where are so many Yangtze swordfish? Don't fool people with that ordinary' lake knife'! "

It turns out that swordfish is divided into "river knife", "lake knife" and "sea knife", and the top grade is "river knife" in the Yangtze River. It is almost impossible to buy real Yangtze river swordfish in Shenyang. The price of real Yangtze river swordfish in its country of origin is as high as three or four thousand yuan per catty.

According to public reports, Shi Weigang, director of the Freshwater Fisheries Research Center and Resource Research Office of the Chinese Academy of Fishery Sciences, said that it is no longer possible to provide reporters with the overall annual output data of river knives after 2002: "As far as I know, there is no authoritative statistics, because the number is too small, it is difficult to count." Lake knife is the "close relative" of Yangtze river swordfish. Because living in a big lake, the taste is far from that of a river knife. Lake knives are often sold as river knives at high prices in the market. Although the appearance is similar, the head is red and the cheeks are white, which can be distinguished by careful identification.