Life habits and morphological characteristics of Songjiang perch (four-gill drum fish)

Songjiang perch (Trachidermus fasciatus) belongs to the order Trachidermus fasciatus, the family Sculpinidae, and the genus Trachidermus fasciatus. Commonly known as: four-gill bass, daughter-in-law fish (Shandong), flower drum fish. English name: Roughskin sculpin, Songjiang sculpin.

Endangerment level: Endangered. China's national level II protected wildlife.

The head and front end of the body are flat, gradually tapering backward and flattened on the sides. The head is large, the mouth is large, end-positioned, slightly tilted. The premaxilla can be retracted, and there are villous fine teeth on the upper and lower jaws and vomer. There are 4 spines on the rear edge of the anterior operculum, the upper spine is large and the tip is hooked upward; there is 1 longitudinal rib on the posterior operculum, and the gill opening is large. The eyes are small, positioned upward on the side, and the edges of the orbits are highly convex, forming the upper edge of the eyes. The body has no scales and there are many small protrusions or skin folds on the skin. There are 2 dorsal fins connected at the base; the pectoral fins are large and round; the pelvic fins are located on the chest; the trailing edge of the caudal fin is slightly rounded. The back of the body is yellowish brown, the belly is grayish white, the sides of the body have black markings, and there are small dark brown spots on the back, head and each fin. There are two orange-yellow diagonal stripes on each gill membrane, just like four exposed gill leaves, so it is called four-gill perch.

The Songjiang perch is a migratory fish found in the warm temperate coastal areas of East Asia. It likes to live in clear running water. They lurk underwater during the day and are active at night. They usually grow and thrive in freshwater river areas connected to the sea. It reaches sexual maturity when it reaches 1 year old, and its body length can reach 120-140 mm. Sexually mature individuals fall into rivers and seas to lay eggs in shallow coastal waters from November to December to January to February of the following year. The initial stage is from November to December. There are more male fish, and more female fish in the later period from January to February. The gonads gradually mature as they swim into seawater. The spawning grounds are in the intertidal zone where there are many oyster reefs. They lay eggs in shell caves. The peak spawning period is from February to March. The cave entrances mostly face south. The water temperature at high tide is 4-5°C and the salinity is 3.0%-3.2%. The number of eggs conceived is 5100-12800. The eggs stick to the top wall of the cave and form a block, guarded by the male fish. They do not ask for food during the breeding period, but ask for food along the coast after breeding. By June, all fish in the sea have returned to freshwater rivers and lakes to feed. The hatched larvae grow into juveniles and then return to freshwater rivers with the tide to grow and fatten from April to May. The slightly larger ones stay in rivers and lakes during the day and emerge at night. Songjiang perch mostly feeds on shrimps and also eats small fish.

This fish is found in the lower reaches of freshwater rivers near the sea in my country, from the mouth of the Yalu River to the mouth of the Jiulong River in Fujian. Among those that enter inland water bodies, the one produced by the Songjiang River in Shanghai is the most famous. It has also been recorded abroad in the west and south of the Korean Peninsula and in Fukuoka and other places in Kyushu, Japan.

The Songjiang perch, the Yellow River carp, the salmon from the Songhua River and the white fish from Xingkai Lake are known as the four famous freshwater fish in my country. They have always been praised by the poet Yake and have been preserved since ancient times. There is a beautiful line: "The west wind blows the four-gill perch, and the cedar is crisp and greasy." Emperor Yang of the Sui Dynasty once praised this fish as "golden sage and jade carp, the best delicacy in the southeast". Since the Eastern Han Dynasty, Songjiang perch has been famous among both the government and the public in my country, and is regarded as a food treasure and tribute. In fact, Songjiang perch is a small fish, with the largest individual being less than 150 mm. Only the Songjiang area has more production, and fishing is popular in autumn and winter. Although the individual is not large, the meat is tender and tender, has no fishy smell, and tastes very good, especially during the egg-laying period. Its liver and cheek meat are very plump, so after it is killed, the internal organs are washed and stuffed back into the belly of the fish. Songjiang perch meat is sweet and warm in nature and has the effect of strengthening the spleen and replenishing qi. It is mainly used to treat spleen deficiency and diarrhea, chronic stomach pain, infantile malnutrition, indigestion, and weight loss.

Songjiang perch was once a very common edible fish along the coasts of Bohai Sea, Yellow Sea and East China Sea in my country. In recent decades, industrial toxic sewage, pesticides, chemical fertilizers, etc. have seriously polluted the vicinity of river mouths, making it difficult for this fish to enter rivers and lakes to feed, fatten and grow; secondly, due to overfishing and the construction of dams, it is now rare .

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