"Flying crab" is a synonym for "Trituberculosis swimming crab". Portunustrituberculatus, commonly known as swimming crab and white crab, belongs to Crustacea, Decapoda, and Portunidae. It is an important economic crab along the coast of China. It grows rapidly and its breeding is highly profitable, and it has become an important breeding species in China's coastal areas.
(1) Water temperature: The adaptable water temperature is 8~31℃, and the optimal growth water temperature is 15.5~26.0℃. In different water temperature environments, the activities of Portunus trituberculatus are different
Portunus trituberculatus
When the water temperature is ~1.5°C, they will not eat, and some individuals freeze to death in shallow water areas; when the water temperature is 0~6°C, they will not eat, and they will hide in the sand day and night, showing a state of resting eyes; when the water temperature is 8~10°C, they will stop eating, and their mobility will be weak. , lurking in deep water; at 14°C, food intake decreases, begins to move to deep areas, and activities are normal; at 15~26°C, food intake is large, activities are normal, and growth is fast; at 17~21°C, mating peaks period; at 14~21℃, egg-bearing groups begin to be found; at 12~14℃, egg laying begins.
(2) Salinity: The adaptable salinity is 13~38‰, and the optimum growth salinity is 20~35‰. The winter adaptation salinity is 28~35‰. When the salinity is lower than 8‰ or higher than 38‰, they stop eating and moving, and all die after one day.
(3) Other factors: the adaptable range of pH value is 7.5~8.; dissolved oxygen cannot be less than 2 mg/L, chemical oxygen consumption generally does not exceed 12 mg/L; hydrogen sulfide does not exceed 0.2 mg/L; the half-lethal concentration of copper ions within 24 hours is 58 mg/L.
Life habits: Swimming crabs lurk on the seabed during the day and come out to look for food at night and have obvious phototaxis. The swimming crabs kept in the pond have obvious diurnal vertical movement in the swimming pool at sunrise and sunset. When a swimming crab swims, its body tilts and hangs upside down in the water, and its fifth step of foot swings frequently, swimming horizontally or undirectionally. When diving into the mud and sand, it is often at an angle of 15 to 45 degrees with the bottom of the pool, with only its eyes and antennae exposed. Swimming crabs have no ability to drill holes, so there is no need to set up defense and escape facilities for pond farming. When the water temperature is below 18°C, swimming crabs mostly lurk in the sand piles beside the pond.
Feeding habits: Swimming crabs are omnivores and like to eat shellfish, fresh fish, small shrimps, etc. They also eat algae shoots, marine animal carcasses and decaying aquatic plants. Moreover, food habits vary at different growth stages. Young crabs tend to be omnivorous at the young crab stage, and the larger the individual, the more carnivorous they tend to be. Usually, they eat less food during the day and eat more in the evening and night. But when the water temperature is below 10℃ and above 32℃, swimming crabs stop eating.
Reproductive habits: Portunus trituberculatus is dioecious. The general life span is 2 years and rarely exceeds 3 years. The smallest biological size is a cephalothorax of 5.1 cm long. The largest male is a cephalothorax of 11 cm, 22 cm wide, and weighs 710 grams. The largest female is a cephalothorax of 10.5 cm long, 22 cm wide, and weighs 730 grams. . The spawning and breeding group is mainly composed of brood crabs that are 1 to 2 years old. The female dies after laying eggs and hatching. Males can die after mating for 2-3 days. The mating time of overwintering Portunus trituberculatus is between July and August every year, while the peak mating period of Portunus crabs born in that year is between September and October.