First, biological characteristics
1. Morphological characteristics: The body of the three-ported crab is composed of head, chest and abdomen, and appendages. It is divided into 20 sections with 5 heads, 8 chests, and 7 abdomen. In the course of evolution, the head and chest healed, called the cephalothorax, with 13 pairs of appendages. Chest 8 has the same pattern of the base of the appendage as Scylla. The abdomen's 7-section pleats are attached to the head and chest. The ratio of the length and width of the abdomen (the length of the 5th to 6th abdominal joints) is approximately 30:1; the abdomen of females is isosceles triangle, and the ratio of length to width is approximately It is 1.75:1; the mated female abdomen is elliptical and the ratio of length to width is 1.25:1.
2, ecological habits: (1) water temperature: adapt to water temperature 8 ~ 31 °C, the optimum growth temperature of 15.5 ~ 26.0 °C. In different water temperature environments, the activities of the three-ported crab are different. When the water temperature is at ~1.5°C, some individuals do not eat, and some individuals die in shallow water. When they are at 0～6°C, they do not ingest food and stay up late for dipping sand to show a state of absent eyes. At 8～10°C, they stop feeding and have weak activity. , Latent in deep water; at 14°C, food intake decreased, began to move to deep areas, normal activities; at 15～26°C, large food intake, normal activities, rapid growth; at 17～21°C, mating peaks Period; at 14-21°C, begin to find the egg-holding group; at 12-14°C, begin to spawn. (2) Salinity: The salinity is 13 to 38 适应, and the optimal salinity is 20 to 35 ‰. The winter adapts to the salinity of 28 to 35 ‰. The salinity was less than 8 ‰ or more than 38 ‰, feeding and activities were stopped and all died after one day.
(3) Other factors: The pH value is in the range of 7.5 to 8. The dissolved oxygen must not be lower than 2 mg/L. The chemical oxygen consumption should not exceed 12 mg/L. The hydrogen sulfide should not exceed 0.2 mg/L. Within 24 hours. The semi-lethal concentration of copper ions is 58 mg/l.
3. Habits: Swim crabs lurk under the sea during the day and feed out at night and have obvious phototaxis. The crabs kept in ponds show a clear vertical shift between day and night at sunrise and sunset. When the crabs swim, the body tilts down in the water, and the fifth step swings frequently to make horizontal or non-directional horizontal swimming. When sneaking into mud sand, it is often at an angle of 15 to 45 degrees with the bottom of the pool, exposing only the eyes and tentacles. The crab does not have the ability to drill holes, and it is not necessary to have anti-escape facilities for pond culture. The water temperature is below 18°C, and the crab is estimated to be in the sand pile beside the pond.
4, feeding habits: Swallow crabs are omnivorous animals, like to eat shellfish, fresh fish, small shrimp, etc., but also ingest algae shoots, dead marine animals and rotting aquatic plants. In addition, during different growth stages, the food habits are different. In the young crab stage, it is omnivorous. The larger the individual is, the more it is carnivorous. It usually eats less during the day and feeds heavily in the evening and at night. However, when the water temperature was below 10°C and above 32°C, the crabs stopped feeding.
5. Breeding habits: Mitochondrial crabs. The general life span is 2 years and rarely exceeds 3 years. The smallest biological type is 5.1 cm in length. The largest male is 11 cm in length, 22 cm in width, and 710 grams in weight. The largest female is 10.5 cm in length, 22 cm in width and weighs 730 grams. . The spawning population consists mainly of 1-2 year old pro-crabs. Females die after hatching. Males can die after 2-3 days of mating. The mating time of the wintering crabs is between July and August of each year, and the maturing crabs of the year are from September to October.
Second, breeding project (farm)
The power supply and water supply should be convenient. The nearby sea area should be free from pollution, low noise, fresh water sources, small trash fish, shellfish and shellfish rich in resources, convenient drainage and drainage. The water depth in small tidal pools should be no less than 0.8 meters, and the depth of large tide pools should be more than 2 meters. Three-ported crabs do not dig and are not good at crawling off the water, so there is no need for fences or fences around the pond.
Third, breeding techniques (stocking season and density)
Before stocking the crabs, the ponds should be dredged and disinfected, and they should be kept in the drain gate to block the nets and be filtered into the seawater by 50 cm. The season in which the Lunar New Year's ungulates are collected in the summer and the crabs in the natural sea area are harvested, and it is also the period of artificial nursery and hatching. In general, 2-3 to 3 cm of juvenile crabs will be 4000 to 5,000 eggs per mu. Ponds with good drainage conditions can be properly placed; ponds with poor drainage conditions can be put less properly.
The crab can also be mixed with fish (salmon, tilapia, milkfish) and shrimp. 30 to 40 fish per acre, and stocking 2000 to 3000 shrimps, can receive the effect of increasing production and income.
IV. Aquaculture Technology (Water Quality Management)
1. Salinity: The range of salinity adaptability of the crab is very wide, usually 1 to 35 ‰. Juvenile crabs have strong adaptability to low salinity, and the optimum salinity for adult crab breeding is 25 ‰.
2. Dissolved Oxygen: Dissolved oxygen in seawater rises with decreasing temperature. The oxygen consumption rate of Portunus trituberculatus increased with the increase of water temperature and decreased with the decrease of water temperature.
3. Transparency: Sea water transparency is closely related to the survival rate of the crab. According to observations, the color of crab ponds should be light green or light brown with a transparency of about 30 cm. If the water is clear, the survival rate of the crab is low.
4. Bottom quality: Three-spotted crabs are suitable for survival in mud-sand bottom sediments, especially sand-bearing sediments. Slurry-rich substrate, containing humus, hydrogen sulfide, and many bacteria, will affect the survival and growth of the crab.
5. The water quality management of water-removing portuguese crabs mainly focuses on two aspects. One is to increase the dissolved oxygen in the water, and the other is to adjust the ratio of pool water. It is required to change the water every 2 to 3 days between June and July, and change the water every 1 to 2 days between August and September. The amount of water exchanged is 1/3 to 1/2 each time. In summer, the salinity of pool water is high. In addition to enhancing the exchange of water, the conditional landlord can introduce fresh water into the pond to keep the salinity of the pool at about 25 , to facilitate the growth of the oyster shell. From October to November, change the water every 3 to 4 days, the weather is not good, the sea is turbid, and the time for changing the water can be appropriately extended. For a relatively small area, stocking density is relatively large, to be equipped with aerobic facilities to meet the oxygen needs of the crab when the shell crab. Pay attention to the observation and recording of the water temperature, salinity, pH, dissolved oxygen, and transparency of the pool water.
6. Feeding: The crabs are omnivorous, and all fresh fish, shrimp, shellfish, crabs and green algae can be used as bait. The amount of feeding varies depending on the size of the crab. The width of the armor is less than 8 cm. The daily feeding amount is 3 to 5% of the overall weight of the crab; the width of the nail is more than 8 cm and the daily feeding amount is 6 to 8 % of the total weight of the crab. Every morning and evening, feed one at a time, and cast more in the evening and less in the morning. Feeding should be adjusted in time according to changes in water temperature and bait status. When the water temperature exceeds 35 °C or less than 14 °C, feeding should be reduced or feeding should be stopped. The three-ported crab also feeds on diets with a protein content of 31%, a particle diameter of 4.8 to 5.6 mm and a particle length of 12 to 19 mm. Using shrimp with the bait, can also receive good results. The similar disability of the crabs occurs when the shells and the severe food are insufficient. Therefore, when the natural foods are not available, they can be fed in a timely manner.
V. Harvesting techniques (hand-printing nets, etc.)
From September to October, the width of the shuttlecock has reached 7 to 8 cm and the weight is about 100 grams. At night or in the early morning, the nets or scorpions are used to catch the shuttle crabs one by one, and the full-bodied yellow crabs are selected and marketed. Light enough plump crabs were put into the pool to continue stocking. From November to December, the crabs were all full, and they were all 11 to 13 cm wide and weighed 150 to 200 grams. The water was collected first to catch male crabs, and then the oviparous developed paste crab was harvested. The harvest method was available. Hand catching or shovel collecting.
1. Morphological characteristics: The body of the three-ported crab is composed of head, chest and abdomen, and appendages. It is divided into 20 sections with 5 heads, 8 chests, and 7 abdomen. In the course of evolution, the head and chest healed, called the cephalothorax, with 13 pairs of appendages. Chest 8 has the same pattern of the base of the appendage as Scylla. The abdomen's 7-section pleats are attached to the head and chest. The ratio of the length and width of the abdomen (the length of the 5th to 6th abdominal joints) is approximately 30:1; the abdomen of females is isosceles triangle, and the ratio of length to width is approximately It is 1.75:1; the mated female abdomen is elliptical and the ratio of length to width is 1.25:1.
2, ecological habits: (1) water temperature: adapt to water temperature 8 ~ 31 °C, the optimum growth temperature of 15.5 ~ 26.0 °C. In different water temperature environments, the activities of the three-ported crab are different. When the water temperature is at ~1.5°C, some individuals do not eat, and some individuals die in shallow water. When they are at 0～6°C, they do not ingest food and stay up late for dipping sand to show a state of absent eyes. At 8～10°C, they stop feeding and have weak activity. , Latent in deep water; at 14°C, food intake decreased, began to move to deep areas, normal activities; at 15～26°C, large food intake, normal activities, rapid growth; at 17～21°C, mating peaks Period; at 14-21°C, begin to find the egg-holding group; at 12-14°C, begin to spawn. (2) Salinity: The salinity is 13 to 38 适应, and the optimal salinity is 20 to 35 ‰. The winter adapts to the salinity of 28 to 35 ‰. The salinity was less than 8 ‰ or more than 38 ‰, feeding and activities were stopped and all died after one day.
(3) Other factors: The pH value is in the range of 7.5 to 8. The dissolved oxygen must not be lower than 2 mg/L. The chemical oxygen consumption should not exceed 12 mg/L. The hydrogen sulfide should not exceed 0.2 mg/L. Within 24 hours. The semi-lethal concentration of copper ions is 58 mg/l.
3. Habits: Swim crabs lurk under the sea during the day and feed out at night and have obvious phototaxis. The crabs kept in ponds show a clear vertical shift between day and night at sunrise and sunset. When the crabs swim, the body tilts down in the water, and the fifth step swings frequently to make horizontal or non-directional horizontal swimming. When sneaking into mud sand, it is often at an angle of 15 to 45 degrees with the bottom of the pool, exposing only the eyes and tentacles. The crab does not have the ability to drill holes, and it is not necessary to have anti-escape facilities for pond culture. The water temperature is below 18°C, and the crab is estimated to be in the sand pile beside the pond.
4, feeding habits: Swallow crabs are omnivorous animals, like to eat shellfish, fresh fish, small shrimp, etc., but also ingest algae shoots, dead marine animals and rotting aquatic plants. In addition, during different growth stages, the food habits are different. In the young crab stage, it is omnivorous. The larger the individual is, the more it is carnivorous. It usually eats less during the day and feeds heavily in the evening and at night. However, when the water temperature was below 10°C and above 32°C, the crabs stopped feeding.
5. Breeding habits: Mitochondrial crabs. The general life span is 2 years and rarely exceeds 3 years. The smallest biological type is 5.1 cm in length. The largest male is 11 cm in length, 22 cm in width, and 710 grams in weight. The largest female is 10.5 cm in length, 22 cm in width and weighs 730 grams. . The spawning population consists mainly of 1-2 year old pro-crabs. Females die after hatching. Males can die after 2-3 days of mating. The mating time of the wintering crabs is between July and August of each year, and the maturing crabs of the year are from September to October.
Second, breeding project (farm)
The power supply and water supply should be convenient. The nearby sea area should be free from pollution, low noise, fresh water sources, small trash fish, shellfish and shellfish rich in resources, convenient drainage and drainage. The water depth in small tidal pools should be no less than 0.8 meters, and the depth of large tide pools should be more than 2 meters. Three-ported crabs do not dig and are not good at crawling off the water, so there is no need for fences or fences around the pond.
Third, breeding techniques (stocking season and density)
Before stocking the crabs, the ponds should be dredged and disinfected, and they should be kept in the drain gate to block the nets and be filtered into the seawater by 50 cm. The season in which the Lunar New Year's ungulates are collected in the summer and the crabs in the natural sea area are harvested, and it is also the period of artificial nursery and hatching. In general, 2-3 to 3 cm of juvenile crabs will be 4000 to 5,000 eggs per mu. Ponds with good drainage conditions can be properly placed; ponds with poor drainage conditions can be put less properly.
The crab can also be mixed with fish (salmon, tilapia, milkfish) and shrimp. 30 to 40 fish per acre, and stocking 2000 to 3000 shrimps, can receive the effect of increasing production and income.
IV. Aquaculture Technology (Water Quality Management)
1. Salinity: The range of salinity adaptability of the crab is very wide, usually 1 to 35 ‰. Juvenile crabs have strong adaptability to low salinity, and the optimum salinity for adult crab breeding is 25 ‰.
2. Dissolved Oxygen: Dissolved oxygen in seawater rises with decreasing temperature. The oxygen consumption rate of Portunus trituberculatus increased with the increase of water temperature and decreased with the decrease of water temperature.
3. Transparency: Sea water transparency is closely related to the survival rate of the crab. According to observations, the color of crab ponds should be light green or light brown with a transparency of about 30 cm. If the water is clear, the survival rate of the crab is low.
4. Bottom quality: Three-spotted crabs are suitable for survival in mud-sand bottom sediments, especially sand-bearing sediments. Slurry-rich substrate, containing humus, hydrogen sulfide, and many bacteria, will affect the survival and growth of the crab.
5. The water quality management of water-removing portuguese crabs mainly focuses on two aspects. One is to increase the dissolved oxygen in the water, and the other is to adjust the ratio of pool water. It is required to change the water every 2 to 3 days between June and July, and change the water every 1 to 2 days between August and September. The amount of water exchanged is 1/3 to 1/2 each time. In summer, the salinity of pool water is high. In addition to enhancing the exchange of water, the conditional landlord can introduce fresh water into the pond to keep the salinity of the pool at about 25 , to facilitate the growth of the oyster shell. From October to November, change the water every 3 to 4 days, the weather is not good, the sea is turbid, and the time for changing the water can be appropriately extended. For a relatively small area, stocking density is relatively large, to be equipped with aerobic facilities to meet the oxygen needs of the crab when the shell crab. Pay attention to the observation and recording of the water temperature, salinity, pH, dissolved oxygen, and transparency of the pool water.
6. Feeding: The crabs are omnivorous, and all fresh fish, shrimp, shellfish, crabs and green algae can be used as bait. The amount of feeding varies depending on the size of the crab. The width of the armor is less than 8 cm. The daily feeding amount is 3 to 5% of the overall weight of the crab; the width of the nail is more than 8 cm and the daily feeding amount is 6 to 8 % of the total weight of the crab. Every morning and evening, feed one at a time, and cast more in the evening and less in the morning. Feeding should be adjusted in time according to changes in water temperature and bait status. When the water temperature exceeds 35 °C or less than 14 °C, feeding should be reduced or feeding should be stopped. The three-ported crab also feeds on diets with a protein content of 31%, a particle diameter of 4.8 to 5.6 mm and a particle length of 12 to 19 mm. Using shrimp with the bait, can also receive good results. The similar disability of the crabs occurs when the shells and the severe food are insufficient. Therefore, when the natural foods are not available, they can be fed in a timely manner.
V. Harvesting techniques (hand-printing nets, etc.)
From September to October, the width of the shuttlecock has reached 7 to 8 cm and the weight is about 100 grams. At night or in the early morning, the nets or scorpions are used to catch the shuttle crabs one by one, and the full-bodied yellow crabs are selected and marketed. Light enough plump crabs were put into the pool to continue stocking. From November to December, the crabs were all full, and they were all 11 to 13 cm wide and weighed 150 to 200 grams. The water was collected first to catch male crabs, and then the oviparous developed paste crab was harvested. The harvest method was available. Hand catching or shovel collecting.
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