Ecological Habits of Green Crab

Green crab is a beach swimming crab, living in the intertidal mudflat or muddy sandy beach, like to stay in the beach puddle and rock crevice and other places. They live in caves during the day and look for food everywhere at night. Especially in the night of high tide, it is more active at night because of its clear eyes and sensitive antennae; in summer, green crabs are more frequent, and when the low tide is shallow, there are many latent mud bottoms to avoid summer heat. Sometimes it can be seen that groups of green crabs use their feet to prop up their bodies and leave the beach with high temperature to enjoy the cool. The activity is less in winter, and the cave is dug near the low tide to spend the winter when the weather is cold. The size and depth of the cave deepens with the increase of individual size and tide area, and the cave in the most exciting part of the area can sometimes reach more than 1 meter. Green crabs in the water rely on the last pair of feet to paddle frequently to the left and right forward, but in most cases move with the current, frightened or encounter obstacles can quickly retreat, crawling on the side of the beach, feeling sensitive, moving freely.

Green crab is a marine crab with wide temperature and wide salt. its living water temperature is 7 ~ 37 °C, the suitable water temperature is 15 ~ 31 °C, and the optimum water temperature is 18 ~ 25 °C. when the water temperature is below 15 °C, the growth slows down obviously, and when the water temperature drops to 7 ~ 8.5 °C. stop feeding and activity, enter dormancy and burrowing state. When the water temperature is above 18 °C, the female crab begins to lay eggs, and the young crabs frequently shed their shells and grow up. When the water temperature rises above 37 °C, the green crab does not feed. When the water temperature rises to 39 °C, the back armour of the green crab appears gray-red spots, and the body gradually ages and dies.

The survival salinity of green crab is 2.6 ‰ ~ 55 ‰, the adaptive range is 6.5 ‰ ~ 33 ‰, and the optimum salinity is 12.8 ‰ ~ 26.2 ‰ (specific gravity 1.010 ~ 1.021). Green crab is difficult to adapt to drastic changes in salinity, salinity sudden change will cause "red awn" and "white awn" two diseases, and even death. Therefore, in the annual plum rain season, due to sudden heavy rain or continuous rainfall in a short period of time, the salinity of artificial culture ponds suddenly changes, which increases the mortality of green crabs.

Green crab has a strong ability to endure dryness. after leaving water, as long as there is a small amount of water in the Gill cavity and the Gill is moist, it can survive for several days or dozens of days.

The eating habits of green crabs are very miscellaneous, mainly animal food. The food composition is mainly molluscs and small crustaceans, and there are often bivalve shell edges, stranded fragments, gastropod mollusks, incomplete spiral shafts, square crab stump limbs and cephalopod fragments in stomach contents. Green crabs often feed on beach worms, small fish and shrimps, and sometimes plant stem and leaf fragments are found in the stomach. Artificially cultured green crabs have no strict choice of bait. Small miscellaneous fish, shrimp, small shellfish (blue clam, Xun's muscle clam, snail, etc.), bean cake and peanut cake can all be eaten. Green crabs have the habit of killing each other. They often prey on soft-shell crabs that have just been shelled.