"Only the wrong name, no wrong nickname", the little yellow fish known as "Xiaoxian" is loved by foodies because of its full umami taste. Regarding its freshness, the literati of ancient times were not less amazed.
For example, Song Dynasty Lou Jian wrote in "Drama After Illness": "From the shame of Zhen, it is really a meal of yellow fish"; Peng Sunyi of the Ming Dynasty sighed: "When you are young, you are gluttonous and fast, but yellow fish is full regardless of money." Although it is not specified in the description whether it is a large yellow croaker or a small yellow croaker, the deliciousness of the two is comparable, and it is not an exaggeration to describe them as "delicacies" and "gluttony".
Wang Wan of the Qing Dynasty described: "At the beginning of the May of the Three Wu Dynasty, the neem trees were supported by rain flowers. At this time, yellow fish is the most beautiful, and the flavor is absolutely superior to that of longbridge bass." Some people may wonder, why is yellow fish the fattest in early May? In fact, the small yellow croaker is a typical marine migratory fish, which only occurs in specific seasons and specific sea areas. So when did it appear and where did it swim? Let's take a look at the small otoliths.
1 Small yellow fish from the "four seas"
Small yellow fish (Larimichthys polyactis), also known as yellow croaker, small fresh, gherkin, etc., belongs to the order Perciformes, totoaba, yellow fish, is a warm temperature near-bottom fish, widely distributed in the East China Sea, the Yellow Sea and the Bohai Sea and the west coast of the Korean Peninsula, generally inhabiting soft mud or sedimentous sea areas, mainly feeding on crustaceans and fish. Small yellow croaker is one of the important marine economic fish in China, and was once known as the traditional Chinese "four seafood" along with large yellow croaker, ribbon fish and cuttlefish.
The small yellow croaker is similar in shape to the large yellow croaker, but they are two different fish. The small yellow fish is smaller, the head is more pointed, the upper and lower mouth are symmetrical, and the scales are larger than that of the large yellow croaker; The large yellow fish is larger, with a blunt head, a protruding lower lip (that is, a bit of a "ground wrap"), and smaller scales. The distribution of the two is also different, small yellow croaker is mainly distributed in the sea area north of 27 °N, west of 125 ° 30'E, the water depth does not exceed 100 m, and the southern Yellow Sea and the northern East China Sea water depth 40~80 m sea area affected by the runoff of the Yangtze River, its distribution range is wider than that of large yellow croaker.
Although the fame of the small yellow croaker is not as loud as that of the big yellow croaker, it is not inferior in nutrition and taste. Small yellow croaker is rich in high-quality protein, unsaturated fatty acids, calcium, phosphorus, iron and other nutrients and trace elements, and is more nutritious than large yellow croaker; In terms of taste and flavor, the large yellow fish has thick meat and more prickly meat, while the small yellow fish has more tender meat and more delicious taste, but slightly more spines.
▲ Photo by Little Yellow Fish|Liang Long
Once the resources of small yellow croaker were very abundant, but after the mid-60s of the 20th century, due to the increasing fishing intensity and environmental degradation, its resources began to decline significantly, and the group structure and biological characteristics also underwent great changes. Since the implementation of the summer season fishing moratorium in the 90s of the 20th century, the resources of small yellow croaker have rebounded significantly. According to the data of China Fishery Statistics Yearbook, from 2011 to 2022, the annual fishing output of small yellow croaker in mainland China will be 268,730~400,650 tons, which occupies an important position in the mainland marine fishery economy.
2 Small otoliths have a big effect
According to the "Records of Wu Di", Wu Wang Lu caught a large number of "golden fish" near the "sandbar", and saw that there was a pair of bony "white stones" in the brains of the fish, so it was named "totoaba". This pair of "white stones" are now called otoliths, fish brain stones, otoliths, etc. Don't underestimate such a pair of small stones, it can make a big difference!
First of all, otoliths can play a role in controlling the balance and hearing of fish, and totoaba can rely on otoliths to find prey and avoid predators. Secondly, the material deposition of otoliths accompanies the entire growth process of the fish, and the growth wheel of its age is recorded. If you put the otolith under the light, you can see that there are alternating light and dark bands on it, the transparent band is wider and the dark band is narrower, the latter is the "growth ring" of the fish, and each dark band represents an age. Finally, otoliths can form specific microchemical structures and morphological differences depending on the physical and chemical composition of the environment. Therefore, otoliths can be used to identify age, study species specificity, early life history, and more.
Through the quantitative analysis of the size and shape of otolith morphology, the biological characteristics of fish are studied, which is called otolith morphology. The research methods of otolith morphology mainly include traditional morphometric method and geometric morphometric method.
The landmark point method is a kind of geometric morphometry, which is a method of quantitatively describing and visualizing the morphological differences and change trends between different groups by analyzing the contour of fish otoliths and the morphological information of the internal auditory groove (main groove) area, which can accurately and intuitively analyze the morphological differences of fish otoliths, so it is widely used in fish species and population differentiation.
▲ Front view of small yellow fish otolith|Photo by Liang Long
▲ Schematic diagram of the landmark point method of small yellow fish otoliths
3 Migration: wintering, baiting, spawning trips
Migration is the active, regular, oriented, clustered, and characteristic horizontal movement of some fish, through migration, changing the water environment in different periods, and successfully completing its life history, such as wintering migration, feeding migration and spawning migration.
Fish migration is a very interesting phenomenon in nature, the most famous being the anadromous migration of the salmon (also known as salmon). After living in the ocean for 3~5 years, the salmon began a thousands of kilometers, tragic journey, during which they not only had to swim against the current, cross the ocean, fly over waterfalls, but also avoid the hunt of all kinds of natural enemies, and after nine deaths, they could swim to their birthplace - inland rivers to spawn and reproduce, and then die exhausted...
The small yellow croaker is also a typical migratory fish, but its migration is not as tragic as that of the salmon. Take the South Yellow Sea as an example: from March to May every year, small yellow croakers migrate to the northern Jiangsu Sea (water depth 10~20 m) to spawn; From June to September, migrate outward to the vicinity of the line of the steamer trawl prohibition zone (water depth 30 m) for baiting. From October to November, it gradually migrates to the open sea for wintering; From December to February of the following year, it winters in the southwestern waters of Jeju Island and the central and southern parts of the East China Sea. In the coastal waters of the mainland, there are sea areas suitable for spawning of small yellow croaker from south to north, and with the rise of water temperature, the spawning peak of small yellow croaker has a latitudinal lag from south to north.
▲ The migration route of the small yellow fish
Whether it is spawning migration or feeding migration, they are closely related to environmental factors such as sea water temperature and salinity. Every year, as the water temperature rises, small yellow croaker will gradually migrate to the shore to spawn, and there is a lag in the peak spawning period, for example, the peak spawning period of Zhoushan fishery is in March, and the peak period of Lüsi fishery is April.
In March, the warm current of Taiwan, mainly affected by high temperature and high salt, went north to the Zhoushan fishing grounds, providing a good spawning environment for small yellow croakers; In April, as the water temperature rises in the Yangtze estuary fishery and is transported by the warm current in Taiwan, small yellow croaker eggs and larvae will spread throughout the Yangtze estuary fishery within the no-fishing zone. In May, due to the poor swimming ability of small yellow croakers, due to the strong tides of the East China Sea and the Southeast Asian monsoon, some of them will follow the Yangtze River to the fresh water and continue north to the adjacent waters of Subei Shoal, at which time the Yangtze River estuary fishery and Lüsi fishing ground become the main breeding grounds for small yellow croaker.
April and May are the peak spawning periods for small yellow croaker in Lüsi Fishery and Haizhou Bay Fishery, when a small amount of eggs and larvae are transported to the vicinity of Haizhou Bay Fishery under the transport of the tidal remnants from the north, so that the Haizhou Bay fishery forms a mixed phenomenon of small yellow croaker.
4 Otolith morphology: divide small yellow fish groups
The diverse habitat history of the small yellow croaker and the different migration routes of the population lead to a diversity of its group structure. The results obtained by different scholars according to the morphological characteristics, geographical distribution, migration routes, fishing logs and other methods of small yellow croaker are also inconsistent, but they can be roughly divided into 2~4 populations. Before the 21st century, the theory of three stocks of small yellow croaker was widely recognized by scholars, that is, small yellow fish stocks can be divided into yellow-Bohai Sea, South Yellow Sea and East China Sea group; After the 21st century, the small yellow croaker population can be divided into two main groups, namely the Bohai-North Yellow Sea and the East Sea-South Yellow Sea group, which are widely recognized, and many later research results support this conclusion.
The same is true of the otoliths of small yellow fish, so the canolith morphology of small yellow fish was analyzed using the landmark point method and its population was divided. 30 1-year-old yellow croakers each from Haizhou Bay Fishery, Lüsi Fishery, Yangtze River Estuary Fishery and Zhoushan Fishery were selected, landmark landmarks 1-11 were selected from the collected digital images of the yaslite, the validity of the landmark data files was calculated, the morphological distortion and variation differences between the mean shapes were compared and analyzed, and finally the relative distortion scores of the small yellow fish otolith morphology of the four geographical groups were analyzed sequentially by principal component analysis and cluster analysis.
The results showed that the morphological difference in the auditory groove area of the small yellow fish otolith was the largest (landmark points 8, 9, 10, 11), and the morphological difference accounted for 91.88% of the total relative distortion. In the principal component analysis, it was found that the small yellow croakers in Lüsi, Yangtze River Estuary and Zhoushan fishery could not be distinguished, and the contribution rates of the first three principal components to the overall variation of otolith morphology were 89.93%, 2.21% and 1.96%, respectively, and the cumulative contribution rate was 94.10%, indicating that they were most likely a group.
▲ Relative distortion fraction No. 1 and No. 2 principal dispersion dot plot and mesh deformation plot
At the same time, it was found that there was a mixed phenomenon of small yellow croaker in the fishery of Haizhou Bay, and some of them overlapped with the above three fisheries and could not be distinguished. Another part of the Haizhou Bay fishery small yellow croaker is divided into a separate group. In the cluster analysis, Lüsi, Yangtze River Estuary and Zhoushan fisheries were the closest European-style and could be clustered into a group, which was far from the Haizhou Bay fisheries, which also indicated that the small yellow croakers in Lüsi, Yangtze River Estuary and Zhoushan fisheries may be one group, and the small yellow croakers in the Haizhou Bay fisheries were quite different.
▲ Morphological clustering analysis results of small yellow otolith in Haizhou Bay, Lüsi, Yangtze River estuary and Zhoushan fisheries
The group problem of small yellow croaker has always been the focus of academic attention, and clarifying the geographical group problem of small yellow croaker is of great significance to its resource conservation and scientific management, and can also make the delicacy of small yellow croaker more served on the table of the people.
Related articles
LIANG Long, SONG Dade, KANG Zhongjie, ZHANG Yushun, LI Guodong, WU Xiaorui, LI Dongjia, WANG Shuyan, YAN Xin, ZHU Fei, XIONG Ying*. Study on population relationship between small yellow croaker in the South Yellow Sea and East China Sea based on otolith landmark method[J]. Southern Fisheries Science. doi: 10.12131/20230120 (click on the paper title for details)
Written by Liang Long
Editor|Ai Hong