What kinds of river crabs are there?

Eriocheir sinensis belongs to Arthropoda, Crustacea, Decapoda, Reptilia, Anura, Cladospora, Toxopoda and Eriocheir sinensis. There are four species of Eriocheir sinensis, namely Eriocheir sinensis, Eriocheir japonica, Eriocheir stenoptera and Eriocheir sinensis (Figure 2- 1). Eriocheir sinensis with narrow forehead and Eriocheir sinensis with straight forehead are not only small in size, but also small in yield and have no economic value; Eriocheir sinensis and Eriocheir japonica, which we usually call Eriocheir sinensis, Eriocheir sinensis, Eriocheir sinensis, Eriocheir sinensis and Eriocheir sinensis, are big, with good meat quality and high yield. Their main differences are:

Fig. 2- Morphological comparison of four species of Eriocheir sinensis.

(1) river crab

The head and breastplate are obviously raised, with four sharp teeth on the forehead edge, the gap between the teeth is deep, and the middle 1 is the deepest. There are six verrucous protrusions behind the forehead angle, four teeth on the front edge, small and obvious teeth on the fourth side, and the toe joints of the last pair of walking feet are sharp claws.

(2) Eriocheir japonica

The head and breastplate are not obviously raised, and there are four sharp teeth on the forehead edge, but there are two blunt teeth in the middle and two sharp teeth outside. The notch between the teeth is shallow, and the middle 1 is the shallowest. There are four warty protrusions behind the forehead, three teeth on the front edge, and the fourth tooth degenerates. The toe joint at the end of 1 is wide and flat.

Eriocheir sinensis is distributed in the coastal provinces of Bohai Sea, Yellow Sea and East China Sea. It has two populations, the northern population is represented by Liaohe (Yellow River) crab, and the southern population is represented by Yangtze (Oujiang) crab. Eriocheir Japonicus is mainly distributed in Guangdong, Guangxi, Fujian, coastal areas of Taiwan Province Province in China, Japan and Russian Far East. It is also divided into two populations, in which the northern population is represented by Suifenhe river system (locally called "Russian crab") and the southern population is represented by Nanliujiang river system (commonly known as "Hepu crab").

The results showed that Liao crab could not adapt to the growing environment in the middle and lower reaches of the Yangtze River after transplanting to the Yangtze River system. Commercial crabs matured 1 month (late August) in advance, molted less times, had small individuals and had poor quality. What's more, Eriocheir sinensis and Eriocheir japonica in Liaohe River system are mixed. Unfortunately, in recent ten years, China's "big crab culture" transplanted crab seedlings from different water systems or different populations to different places for culture, resulting in the mixed germplasm resources of Eriocheir sinensis in different water systems, and the loss of its intangible assets is immeasurable. Therefore, in production, it is forbidden to transplant crabs from different water systems to other water systems for breeding.