At present, the cultivation methods of river crabs in various provinces and cities in the south are mainly ponds for raising crabs, lake nets for keeping crabs, rice fields for raising crabs, small lakes and small reservoirs for crabs. Heilongjiang Province is located in the high-cold zone. The relatively mature technology in the south cannot be fully applied in this province. According to the characteristics of the ecological environment in the high-cold area, combined with the living habits of different strains of crabs, a new breed of breeding techniques has been developed. Since 1999, we have conducted research and experiments on crab farming techniques in Dashuimyeon in high-cold areas. Through three years of exploration, we have accumulated a certain degree in selection, stocking, escape prevention, fishing, disease prevention, long-distance transportation, and breeding patterns of crab strains. Experience laid the foundation for the large-scale industrial production of crabs in high-cold areas.
First, the choice of large-surface breeding sites According to the biological characteristics of river crabs, based on the investigation of large-surface water resources, two reservoirs have been selected as our experimental reservoirs: Nihe Reservoir and Donghu Reservoir.
Both Nihe Reservoir and Donghu Reservoir are large-scale plain reservoirs, located in the Songnen Plain. The terrain around the reservoir area is gentle, both cultivated land or grassland. The water surface is open, the water level is shallow, and the sediment quality is flat. The soil is dominated by chernozem and meadow soil. The main dam is a homogenous earth dam with sub-clay. The slope is made of stone concrete to protect the slope. The slope ratio is about 1:2.7. The auxiliary dam is a homogeneous soil dam .
The main difference between the two reservoirs is that the water level in the Nihe Reservoir changes significantly. The water level is 509.84m3/sec when the Xingli water level is 133.5m; the water discharge is 389.4m3/sec when the water level is 132.5m; the water level is 131.5m. At the time of discharge, the discharge amount was 185.14m3/sec; at dead water level, the discharge amount was 103.1m3/sec; while the water level of Donghu Reservoir did not change substantially.
II. Selection, transportation and stocking of crab seedlings
1. Selection of strains Currently, crabs used for breeding in China are derived from three water systems, namely the Yangtze River, Liaohe and Lancang water systems. Due to differences in geographical environment and geographical population of the original life, the crabs of three different river systems lead to different morphological characteristics and ecological habits, and the breeding effects are quite different.
The river crabs in the Yangtze River system are irregularly oval; gold claws are yellow hairy, and the shells are white-bellied; the bristly hairs are dense and have a long footing; they begin to swim in mid-September, and the coldness to the peak of frost formation forms, and the flood season is obvious and concentrated.
The river crabs of the Liaohe River system are also irregularly oval; the back shell is yellowish and the abdomen is gray; the bristles are sparse and the steps are short; the migration time is the earliest of the three strains, and generally starts crawling in mid-August and continues through November. It does not form a flood season.
The Jiangjiang crab is approximately square; the back is gray and black, and the abdomen is yellowish; the bristles are sparse, and the steps are short; generally the crawls begin in late October and continue until the second year of January, when the cold wave falls.
Judging from the breeding effect, the Yangtze River Crab has the fastest growth rate. The specifications for the second autumn age are 150g/only ~250g/only. The specifications are neat, the group gains 7 to 10 times the weight, and the catch rate can reach 30% to 40%. Liaohe Crab's second autumn age specification is 100g/only ~ 150g/only, the specifications are relatively neat, the group gains weight 3~5 times, the catch-up rate is up to 20%. Ganjiang Crab Erqiu specifications for the 80g / only ~ 150g / only, the size of the uneven, group weight gain 1 to 3 times, the rate of recovery was only 1%.
A comprehensive study comparing three different river crabs, taking into account the transport distance and the early winter in Heilongjiang Province, in order to facilitate management and obtain the highest economic benefits, we chose the Liao river crab with the earliest migrating time and not easy to form the flood season to conduct breeding experiments in alpine areas. .
2. Quality identification First of all, from the purchase of crabs to understand the production process of crab seedlings, natural crabs, natural seawater hatching crabs, artificial seawater hatching crabs or wells hatching crab seedlings? And feeding, desalination and other conditions. Second, observe the appearance. The specifications are neat, the body is yellow-brown, lively and agile, and it is very quick to escape immediately after releasing the grip. Finally, use the dry test. Take a certain number of young crabs wrapped with gauze, put it in the shade and check it after 10 hours. If there is no death, it is a good quality, high quality, high quality crab seedling.
3. Buckle crab transportation (1) Crab box preparation.
The crab seedlings box is a polyethylene foam sealed incubator box, with a specification of 700mm350mm280mm, with 3 ventilation and observation holes on each side of the box, and 1 ventilation and observation hole on each side. The specification of the hole is 10cm4cm.
(2) Crab Packing.
The treated crabs were put into a yarn bag. Each bag was loaded with 7.5 kg of crabs, and each two bags were filled with a crab seedling box. The key to the technology is that each yarn bag must be bundled and solid, so that there is no room for any movement of the dungeon. The lid must be firm and securely taped.
(3) Deduction crab transport.
Use a sealed and insulated car to put the box of crabs in order to keep them stable and strong, preventing them from being dumped or bumped.
(4) Crab stocking.
The stocking site was chosen to be midstream in the reservoir, and 100m to 200m away from the shore. The stocking site requires rich aquatic resources with a depth of 80cm to 150cm under the ice, and the bottom sediment is silt, away from the dam and upstream and downstream outlets.
4. River crab management (1) establishment of anti-escape anti-theft facilities.
Three barriers are set at the upstream inlet, downstream outlet, and each irrigation hole and flood discharge gate, and a gabion is attached to the bottom.
For the reservoir, the area is large and the resources are abundant. The river crab will not run away, but the management is troublesome. Therefore, when choosing a reservoir, try to choose an empty place, and build a small house on the side of the reservoir for people who use it for day-to-day management to facilitate patrols.
(2) Daily management.
During crab breeding, observe crab climbing and feeding. Repeated inspections of the main and secondary dam bodies and the sinking area revealed that the cave was repaired in time. Send special personnel to manage carefully, strengthen the inspection of the warehouse, and do a good job of flood prevention and flight prevention in the rainy season, control the water level, prevent submergence and block the network, check whether the block has been damaged, and find that the damage should be promptly repaired.
5. Crab fishing (1) Fishing time: mid-August to early October.
(2) Fishing methods: cages, net foils, gill nets, etc.
6. The crabs captured by the temporary reservoirs of adult crabs are kept in ponds. The yellow and black soils are better for the bottom of the pond to prevent affecting the crab color and meat quality. Maintain the water depth of the holding pool of 1.5m. There should be a proper amount of aquatic plants and aquatic plants such as reeds, water peanuts and so on. A plastic film wall should be set around the pond, and a certain amount of land should be reserved for crabs to stay up and go for food. The method is: about 20cm plastic film buried in the soil, 60cm ~ 70cm exposed outside, in the outer part every 30cm ~ 50cm with two pieces of bamboo sandwiched and supported. In order to prevent the crabs from escaping, they must also use the nets at the entrance and exit to block the loopholes and at the same time control and eliminate rats and other enemies.
When releasing crabs, place the crabs on the edge of the pond and allow them to climb into the water and remove the weak crabs. When feeding, it is necessary to set point, time, quality and quantity to increase the feeding amount of wild fish. At the same time, it is necessary to strengthen the management of the holding period: diligent ponds, diligent observations, frequent water changes, diligent efforts to clean the food farms, strengthen the prevention of escape, keep the crab pool clean, and promote the rapid growth of crab weight. You can also feed some soy or beancakes.
The crabs to be sold are kept in cages, fed in small quantities, restored to their constitution, and cleared mud from muddy water to facilitate long-distance transportation.
Third, the results and discussion
1. Growth and catching of river crabs in high cold areas.
The crabs were cultured in large water surface in the high-cold area for 4 months. The average size reached 100g/body, and the largest individuals were 200g/body, and the rate of catchback was as high as 31%. The results showed that the selected river crab species and 160/kg to 260/kg river crab species were more suitable for large water surface culture in high-cold areas.
2. Crab breeding large water surface options.
The large water surface of crabs, lakes, reservoirs, and marshes can all be raised, but water resource investigations should first be conducted, including plankton, macrobenthos, and aquatic vascular plants. In addition, the investigation of the natural state of the waters should be carried out, including analysis of water chemistry, water depth and flatness of the bottom of the reservoir. Fresh water, abundant dissolved oxygen, abundant feed, shallow water levels, and plain lakes or reservoirs rich in aquatic vegetation are the best choices for river crab breeding waters on large water surfaces.
3. The date of launching and the stocking amount of crab breeding in Dashui surface were determined.
Heilongjiang Province is located in the high-cold area, with low winter temperatures and long ice-sealing periods. There are no crabs distributed under natural conditions. Therefore, we chose to place crab seedlings in spring. It is generally believed that the stocking of crabs should be carried out in late October in the fall. At this time, the water temperature is low, crab activity is weak, and the possibility of flight is reduced. At the same time, the ferocious fish's feeding intensity is reduced, and they are in a state of starving, which is harmful to crab seedlings. It is small and improves the survival rate of crab seedlings. In addition, the crab seedlings will be able to adapt to the environment of the reservoir better than the spring-released six-month recovery period. In the following year, the snow and ice melt and quickly ingest food and grow. However, if the water level is shallow, the stocking of crabs in autumn should consider the possibility of freezing.
For large river crabs, the number of fry stocks should be determined based on the survey results of the water resources. The resources are in good condition, aquatic vascular plants are abundant, the amount of benthic animals is large, and the bottom of the reservoir is flat, etc. It can be put in more or less, or less. In general, the amount of detained crab should not exceed 1kg/1000m2, because crabs consume a large amount of bait resources.
4. Determination of time for catching crabs in rivers with large water surface and factors affecting catchback.
The core technology of large-water crab breeding is to choose the best time for arrest. Premature catching, crabs have poor plumpness, affecting economic efficiency; catching too late may result in large numbers of crabs fleeing or staying motionless, preparing to overwinter, affecting the number of catches, and thus reducing production. To this end, we began organizing fishing in mid-August and continued until the beginning of October. Judging from the monthly catches, there is little difference between the mid-to-late August and the individuals are slightly young. Crabs and crab paste are not yet mature, but the crabs are full. The crab production is mainly concentrated in mid-September, accounting for 47.2% of the total output, and the individuals are larger and have better maturation, crab crab and crab paste are full.
Factors affecting the time of arrest are: temperature, cold wave, and wind direction. In the catch season, the higher the temperature is, the higher the catch will be. When the northwest wind and the northeast wind are blown, the catch will be higher.
5. The best fishing method for big river crabs.
The experiment found that among the three fishing methods: net foil, ground cage, and gill net, the best fishing effect with dense mesh nets is that the crabs are not damaged, the survival rate is high, and the yield is concentrated, and it can also effectively prevent crabs from fleeing.
First, the choice of large-surface breeding sites According to the biological characteristics of river crabs, based on the investigation of large-surface water resources, two reservoirs have been selected as our experimental reservoirs: Nihe Reservoir and Donghu Reservoir.
Both Nihe Reservoir and Donghu Reservoir are large-scale plain reservoirs, located in the Songnen Plain. The terrain around the reservoir area is gentle, both cultivated land or grassland. The water surface is open, the water level is shallow, and the sediment quality is flat. The soil is dominated by chernozem and meadow soil. The main dam is a homogenous earth dam with sub-clay. The slope is made of stone concrete to protect the slope. The slope ratio is about 1:2.7. The auxiliary dam is a homogeneous soil dam .
The main difference between the two reservoirs is that the water level in the Nihe Reservoir changes significantly. The water level is 509.84m3/sec when the Xingli water level is 133.5m; the water discharge is 389.4m3/sec when the water level is 132.5m; the water level is 131.5m. At the time of discharge, the discharge amount was 185.14m3/sec; at dead water level, the discharge amount was 103.1m3/sec; while the water level of Donghu Reservoir did not change substantially.
II. Selection, transportation and stocking of crab seedlings
1. Selection of strains Currently, crabs used for breeding in China are derived from three water systems, namely the Yangtze River, Liaohe and Lancang water systems. Due to differences in geographical environment and geographical population of the original life, the crabs of three different river systems lead to different morphological characteristics and ecological habits, and the breeding effects are quite different.
The river crabs in the Yangtze River system are irregularly oval; gold claws are yellow hairy, and the shells are white-bellied; the bristly hairs are dense and have a long footing; they begin to swim in mid-September, and the coldness to the peak of frost formation forms, and the flood season is obvious and concentrated.
The river crabs of the Liaohe River system are also irregularly oval; the back shell is yellowish and the abdomen is gray; the bristles are sparse and the steps are short; the migration time is the earliest of the three strains, and generally starts crawling in mid-August and continues through November. It does not form a flood season.
The Jiangjiang crab is approximately square; the back is gray and black, and the abdomen is yellowish; the bristles are sparse, and the steps are short; generally the crawls begin in late October and continue until the second year of January, when the cold wave falls.
Judging from the breeding effect, the Yangtze River Crab has the fastest growth rate. The specifications for the second autumn age are 150g/only ~250g/only. The specifications are neat, the group gains 7 to 10 times the weight, and the catch rate can reach 30% to 40%. Liaohe Crab's second autumn age specification is 100g/only ~ 150g/only, the specifications are relatively neat, the group gains weight 3~5 times, the catch-up rate is up to 20%. Ganjiang Crab Erqiu specifications for the 80g / only ~ 150g / only, the size of the uneven, group weight gain 1 to 3 times, the rate of recovery was only 1%.
A comprehensive study comparing three different river crabs, taking into account the transport distance and the early winter in Heilongjiang Province, in order to facilitate management and obtain the highest economic benefits, we chose the Liao river crab with the earliest migrating time and not easy to form the flood season to conduct breeding experiments in alpine areas. .
2. Quality identification First of all, from the purchase of crabs to understand the production process of crab seedlings, natural crabs, natural seawater hatching crabs, artificial seawater hatching crabs or wells hatching crab seedlings? And feeding, desalination and other conditions. Second, observe the appearance. The specifications are neat, the body is yellow-brown, lively and agile, and it is very quick to escape immediately after releasing the grip. Finally, use the dry test. Take a certain number of young crabs wrapped with gauze, put it in the shade and check it after 10 hours. If there is no death, it is a good quality, high quality, high quality crab seedling.
3. Buckle crab transportation (1) Crab box preparation.
The crab seedlings box is a polyethylene foam sealed incubator box, with a specification of 700mm350mm280mm, with 3 ventilation and observation holes on each side of the box, and 1 ventilation and observation hole on each side. The specification of the hole is 10cm4cm.
(2) Crab Packing.
The treated crabs were put into a yarn bag. Each bag was loaded with 7.5 kg of crabs, and each two bags were filled with a crab seedling box. The key to the technology is that each yarn bag must be bundled and solid, so that there is no room for any movement of the dungeon. The lid must be firm and securely taped.
(3) Deduction crab transport.
Use a sealed and insulated car to put the box of crabs in order to keep them stable and strong, preventing them from being dumped or bumped.
(4) Crab stocking.
The stocking site was chosen to be midstream in the reservoir, and 100m to 200m away from the shore. The stocking site requires rich aquatic resources with a depth of 80cm to 150cm under the ice, and the bottom sediment is silt, away from the dam and upstream and downstream outlets.
4. River crab management (1) establishment of anti-escape anti-theft facilities.
Three barriers are set at the upstream inlet, downstream outlet, and each irrigation hole and flood discharge gate, and a gabion is attached to the bottom.
For the reservoir, the area is large and the resources are abundant. The river crab will not run away, but the management is troublesome. Therefore, when choosing a reservoir, try to choose an empty place, and build a small house on the side of the reservoir for people who use it for day-to-day management to facilitate patrols.
(2) Daily management.
During crab breeding, observe crab climbing and feeding. Repeated inspections of the main and secondary dam bodies and the sinking area revealed that the cave was repaired in time. Send special personnel to manage carefully, strengthen the inspection of the warehouse, and do a good job of flood prevention and flight prevention in the rainy season, control the water level, prevent submergence and block the network, check whether the block has been damaged, and find that the damage should be promptly repaired.
5. Crab fishing (1) Fishing time: mid-August to early October.
(2) Fishing methods: cages, net foils, gill nets, etc.
6. The crabs captured by the temporary reservoirs of adult crabs are kept in ponds. The yellow and black soils are better for the bottom of the pond to prevent affecting the crab color and meat quality. Maintain the water depth of the holding pool of 1.5m. There should be a proper amount of aquatic plants and aquatic plants such as reeds, water peanuts and so on. A plastic film wall should be set around the pond, and a certain amount of land should be reserved for crabs to stay up and go for food. The method is: about 20cm plastic film buried in the soil, 60cm ~ 70cm exposed outside, in the outer part every 30cm ~ 50cm with two pieces of bamboo sandwiched and supported. In order to prevent the crabs from escaping, they must also use the nets at the entrance and exit to block the loopholes and at the same time control and eliminate rats and other enemies.
When releasing crabs, place the crabs on the edge of the pond and allow them to climb into the water and remove the weak crabs. When feeding, it is necessary to set point, time, quality and quantity to increase the feeding amount of wild fish. At the same time, it is necessary to strengthen the management of the holding period: diligent ponds, diligent observations, frequent water changes, diligent efforts to clean the food farms, strengthen the prevention of escape, keep the crab pool clean, and promote the rapid growth of crab weight. You can also feed some soy or beancakes.
The crabs to be sold are kept in cages, fed in small quantities, restored to their constitution, and cleared mud from muddy water to facilitate long-distance transportation.
Third, the results and discussion
1. Growth and catching of river crabs in high cold areas.
The crabs were cultured in large water surface in the high-cold area for 4 months. The average size reached 100g/body, and the largest individuals were 200g/body, and the rate of catchback was as high as 31%. The results showed that the selected river crab species and 160/kg to 260/kg river crab species were more suitable for large water surface culture in high-cold areas.
2. Crab breeding large water surface options.
The large water surface of crabs, lakes, reservoirs, and marshes can all be raised, but water resource investigations should first be conducted, including plankton, macrobenthos, and aquatic vascular plants. In addition, the investigation of the natural state of the waters should be carried out, including analysis of water chemistry, water depth and flatness of the bottom of the reservoir. Fresh water, abundant dissolved oxygen, abundant feed, shallow water levels, and plain lakes or reservoirs rich in aquatic vegetation are the best choices for river crab breeding waters on large water surfaces.
3. The date of launching and the stocking amount of crab breeding in Dashui surface were determined.
Heilongjiang Province is located in the high-cold area, with low winter temperatures and long ice-sealing periods. There are no crabs distributed under natural conditions. Therefore, we chose to place crab seedlings in spring. It is generally believed that the stocking of crabs should be carried out in late October in the fall. At this time, the water temperature is low, crab activity is weak, and the possibility of flight is reduced. At the same time, the ferocious fish's feeding intensity is reduced, and they are in a state of starving, which is harmful to crab seedlings. It is small and improves the survival rate of crab seedlings. In addition, the crab seedlings will be able to adapt to the environment of the reservoir better than the spring-released six-month recovery period. In the following year, the snow and ice melt and quickly ingest food and grow. However, if the water level is shallow, the stocking of crabs in autumn should consider the possibility of freezing.
For large river crabs, the number of fry stocks should be determined based on the survey results of the water resources. The resources are in good condition, aquatic vascular plants are abundant, the amount of benthic animals is large, and the bottom of the reservoir is flat, etc. It can be put in more or less, or less. In general, the amount of detained crab should not exceed 1kg/1000m2, because crabs consume a large amount of bait resources.
4. Determination of time for catching crabs in rivers with large water surface and factors affecting catchback.
The core technology of large-water crab breeding is to choose the best time for arrest. Premature catching, crabs have poor plumpness, affecting economic efficiency; catching too late may result in large numbers of crabs fleeing or staying motionless, preparing to overwinter, affecting the number of catches, and thus reducing production. To this end, we began organizing fishing in mid-August and continued until the beginning of October. Judging from the monthly catches, there is little difference between the mid-to-late August and the individuals are slightly young. Crabs and crab paste are not yet mature, but the crabs are full. The crab production is mainly concentrated in mid-September, accounting for 47.2% of the total output, and the individuals are larger and have better maturation, crab crab and crab paste are full.
Factors affecting the time of arrest are: temperature, cold wave, and wind direction. In the catch season, the higher the temperature is, the higher the catch will be. When the northwest wind and the northeast wind are blown, the catch will be higher.
5. The best fishing method for big river crabs.
The experiment found that among the three fishing methods: net foil, ground cage, and gill net, the best fishing effect with dense mesh nets is that the crabs are not damaged, the survival rate is high, and the yield is concentrated, and it can also effectively prevent crabs from fleeing.
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