The young sweetfish hatched in late autumn go down to the nearby sea and winter off the coast. The following year, in March-April, they climb to the upper streams of the river and live, then descend to the river estuary where the sea is close to lay eggs in September-October, the spawning season. After spawning, both males and females die. The sweetfish forms a sphere of influence and drive out all the fish that invade it, and there is a fishing method called 'Nolim Fishing' that uses this habit. It has a good scent like watermelon, and it is popular for high-end food. Recently, Plecoglossus altivelis has been found in large lakes such as Andong Lake, Daecheong Lake, Unam Lake, and Paldang Lake.
Shape of SweetfishThe body is long and slim to the side. The head is large and the snout is pointed. The mouth is very large, and the lips are parallel and thick and white. There is a rake-shaped projection in front of the upper jaw. The lower and upper teeth of the mother are comb-shaped. There is no moustache. The anal fin ends at the middle point of the adipose fin.
Color of SweetfishOverall it is silver. The back is grayish brown or blueish brown, and the belly side is silvery white. During the spawning period, the males are generally black, the chest and abdomen are red, and the fins are yellow.
Life of SwetfishThe sweetfish lives on the coast when it is young. It goes up to the river in spring and goes down to the estuary during spawning.
Food-habits of SweetfishWhen they are young, they feed on zooplankton in the sea, and after returning to the river, they feed on epilithic algae and microorganisms.
Distribution of SweetfishSweetfish are mostly distributed in rivers across the country that flow along the coast, but their habitats have decreased a lot due to water pollution. They are distributed in Japan, Taiwan, and parts of China.
As you pass the Dongcheon River, where there is an extraordinary amount of sand, you will encounter sweetfish that move exceptionally in the water. Sweetfish, which occupy the dominant species of Dongcheon River, are the protagonist.
It seems that in the old days people considered sweet fish very valuable. Mr. Soo-gwang Lee's 『Jibong Yuseol』 introduces sweet fish in detail. “Sweetfish come up from the sea to the river in spring, gain weight and grow in summer and autumn, and disappear in late autumn.” In addition, Mr. Yu-gu Seo wrote in "Nanhoeomok" published in 1820, "II has fine scales, black back, and gray-white belly. Since it has a straight bone in its snout, it is silver-white, so it is named like that. Fat is stuck on the spine, so it tastes light and does not have a fishy smell. When it is alive, it has cucumber smell. It is unusually tasty among fish. If you pickle it in salt, you can send it far away, and if you eat it grilled, it has a scent and tastes good. Some of the larger ones are about 30 cm long. They are found in streams and mountain streams here and there”.
Mr. Soo-kwang Lee's 『Jibongyuseol』 is the first publication to introduce the ecological characteristics of sweetfish in Korea, and it can be confirmed that sweetfish was used for food in the past. It is the first record to report that sweetfish come up from the sea and that some sweetfish remain undead in winter.
Sweetfish settle in a place where there are pebbles on the bottom and clear water, and lord it over outsiders. They keep an area of about 1 square meter and prevent other sweetfish from entering. By using this habit of snarling sweetfish in reverse, it uses an alive sweetfish to catch another sweetfish.
They grow by eating diatoms or microorganisms on pebbles or stones. The time to lay eggs is from September to October. Females and males descend to the lower stream close to the sea and lay eggs on sand or gravel. At this time, the male's whole body turns into a beautiful silver color and takes on a marriage color. One female followed by several males makes a fuss. The baby sweetfish, awakening from the egg, goes down to the sea and spends winter.