Donggang Portunus sinensis, a specialty of Donggang City, Liaoning Province, is a national geographical indication of agricultural products.[1-2]
Donggang Portunus trituberculatus, commonly known as Portunus trituberculatus and white crab, belongs to Crustacea, Decapoda and Portunus.Portunus sinensis growing in the Yellow Sea area of Donggang has a longer cycle because of the low water temperature in the growth environment, and its meat quality is more delicious than that of Portunus sinensis in other areas and cultured.
The swimming crab is the most robust in the winter migration season, generally weighing about 250g, and the maximum weight can reach more than 500g.The female crab red paste is full, and the taste is excellent.Portunus sinensis can be eaten fresh, steamed, fried, or fried, or stewed with bean paste in half, or fried with crabs, such as rice cakes, pickles, and tofu. It is a common dish on the table of coastal residents.It can also be pickled, that is, fresh swimming crabs can be soaked in brine and eaten a few days later, commonly known as "Xinfeng Choke Crab".In the past, because of the high production of swimming crabs, fishermen often selected live crabs filled with paste, and removed the yellow crabs into bowls, which were solidified in the wind and the sun to form "crab yolk cake", which has a very good flavor.[3]
On September 13, 2011, the Ministry of Agriculture of the People's Republic of China approved the registration and protection of geographical indications of agricultural products for "Donggang Portunus".[1-2]
Chinese name
Portunus donggang
name of origin
Donggang City, Liaoning Province
Quality characteristics
The meat is tender, rich in nutrition, and tastes good
geographical indication
Geographical indications of agricultural products of the Ministry of Agriculture
The appearance of Donggang Portunus sinensis is large, plump, with obvious body lines, bright colors, no black spots, and no stomach prints on the upper navel.Vitality, the pincers are closely connected with the body, and do not sag.The gill filaments are clear, white or brownish, and free of foreign matter.The tissue is plump, the abdomen is close to the central groove, the fingers press the abdomen firmly, the meat is tight and elastic, it is not easy to peel off, and the crab roe is solidified and does not flow.Smell, with the inherent fresh and fishy smell of fresh crab, without peculiar smell.[2]
Portunus donggang
Intrinsic quality
The intrinsic quality of Donggang Portunus sinensis requires delicate, white meat, rich in protein, fat and various minerals, and the best taste. The edible part accounts for 52%.The nutritional composition of Portunus donggang contains 956 mg aspartic acid (ASP), 433 mg threonine (THR), 479 serine (SER), 1435 mg glutamic acid (gram LU), 652 mg glycine (gram LY), 570 mg alanine (ALA), 53 mg cystine (CYS), 474 mg valine (VAL), 183 mg methionine (meter ET) and isoleucine (ILE) per 100 grams366 mg, leucine (LEU) 685 mg, tyrosine (TYR) 360 mg, phenylalanine (PHE) 463 mg, lysine (LYS) 575 mg, ammonia (NH3) 140 mg, histidine (HIS) 182 mg, arginine (AR g) 773 mg, proline (PRO) 586 mg, calcium 1.03 mg, magnesium 825 mg, zinc 32.9 mg, eicosapentaenoic acid (EPA) (accounting for total fat)13.70%, docosahexaenoic acid (DHA) (14.12% of total fat), monounsaturated fatty acid (338.0% of total fat), polyunsaturated fatty acid (29.09% of total fat).[2]
Production environment
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Climatic conditions
Liaoning ProvinceYalu River Estuary Fishing Ground and Yuanshan Fishing Ground near Donggang City belong to the marine monsoon climate zone in the humid area of the southern temperate zone, so they have their own characteristics.First, the climate condition is superior. Influenced by the monsoon all the year round, it has the climate characteristics of rain and heat in the same season, water and heat together, and abundant light, temperature and water resources.Second, the monsoon climate is characterized by obvious seasonal changes in the prevailing wind direction throughout the year and significant seasonal climate differences are generated with the change of wind direction.Third, the climate elements change rapidly. Because of the proximity to land, the two different underlying surfaces of sea and land jointly affect the marine climate, and its climate characteristics are bound to have dramatic changes in meteorological elements.The fourth is the frequent disastrous weather. The sea area is located in the mid latitude area, where the south-north airflow intersects Suiyuan. Various weather systems are active frequently, and disastrous weather can occur throughout the year.
Temperature.The trend of temperature change in the fishing ground is that the temperature gradually increases from north to south. The average annual temperature of the adjacent land is 9.1 ℃, while the average annual temperature of the fishing ground at the southernmost end is 10.8 ℃, 1.7 ℃ higher.The monthly average temperature is January - 6.6 ℃, February - 4.9 ℃, March 1.3 ℃, April 8.1 ℃, May 13.8 ℃, June 18.3 ℃, July 22.2 ℃, August 23.7 ℃, September 19.5 ℃, October 12.7 ℃, November 4.1 ℃, December - 3.5 ℃, and the annual average temperature is 9.1 ℃.
Precipitation.Due to the comprehensive influence of different thermal properties and dynamic factors of sea and land, the precipitation of fishing ground is basically parallel to the coastline, and decreases from coast to sea. The annual average precipitation is 642.7 mm.
Wind.The seasonal changes of the temperature gradient and pressure gradient of the fishing ground are obvious, so the monsoon is strong. The northerly wind prevails in winter, and the southerly wind prevails in summer. The wind direction is changeable in the transitional seasons of spring and autumn.The monthly average wind speed is 7.0m/s in January, 5.8m/s in April, 4.5m/s in July, 6.1m/s in October, and 5.8m/s in the whole year.[2]
Marine hydrology
Water temperature.Water temperature is a unique quantity representing the amount of heat obtained by seawater, and is one of the most basic and important marine hydrological elements. The main monitoring indicators are horizontal distribution and vertical distribution.First, the water temperature in the plane distribution in May is 9.1 ℃ in the mean value of the surface layer, 7.8-11.5 ℃ in the range, 8.2 ℃ in the mean value of 15 meters, 7.4-9.1 ℃ in the range, 8.3 ℃ in the mean value of the bottom layer, 7.2-11.2 ℃ in the range;The average water temperature in August is 25.4 ℃ in the surface layer, 23.4-28.7 ℃ in the range, 23.6 ℃ in the 15 meters, 20.8-24.8 ℃ in the range, 23.6 ℃ in the bottom layer, 20.4-25.7 ℃ in the range.The second is vertical distribution, with thermocline phenomenon, whose depth is generally between five meters and the bottom layer. The strength of the thermocline is 0.49 ℃/m in the east, 0.25 ℃/m in the west, and 0.20 ℃/m in the south.
Salinity.Seawater salinity is one of the most basic and important factors in marine hydrology.It not only represents the chemical properties of seawater, but also has a direct or indirect relationship with most marine hydrological phenomena.The horizontal distribution of salinity in the fishing ground The salinity in the south is the highest, and the lowest in the north from high to low is higher in the south than in the east than in the west.This feature fully reflects the significant impact of fresh water runoff.The average salinity is 24.56 ‰ in the east, 24.41 ‰ in the west, 26.98 ‰ in the south and 23.34 ‰ in the north.The vertical variation of the salinity of the fishing ground is that the average salinity difference of the bottom layer is very small. In the north, it is 21.48 ‰ of the surface layer, 21.46 ‰ of the bottom layer, 22.95 ‰ of the eastern surface layer, 23.97 ‰ of the bottom layer, 24.01 ‰ of the southern surface layer, 24.64 ‰ of the bottom layer, 21.49 ‰ of the western surface layer, and 22.86 ‰ of the bottom layer.
tide.The tidal system of the fishing ground is formed by the tidal waves from the Pacific Ocean under the influence of complex coastal and seabed morphology, and the tidal nature is regular semidiurnal tide.The average tidal range is 4.08m, and the maximum tidal range is 6.38m.The average sea level is 0.36m (data period: July September 1983).The average high tide level, the highest tide level, the average low tide level and the lowest tide level are 2.34m, 3.79m, 1.75m and 2.68m respectively.
ocean current.Current consists of current and residual current.The current velocity in the west sea area of the fishing ground is strong, while that in the southeast is weak.The average tidal current velocity is 42cm/s in the north surface layer, 40cm/s in the bottom layer, 34cm/s in the east surface layer, 28cm/s in the bottom layer, 43cm/s in the south surface layer, 33cm/s in the bottom layer, 49cm/s in the west surface layer and 43cm/s in the bottom layer.In the western sea area, not only the tidal current speed is high, but also the residual current speed is relatively high. The maximum residual current speed in the surface and bottom layers are 23.8cm/s and 24.8cm/s respectively. The average residual current velocity during spring tide is 21.8cm/s in the northern surface layer, 262 ° in the flow direction, 18.1cm/s in the bottom layer, 245 ° in the flow direction, 10.9cm/s in the eastern surface layer, 262 ° in the flow direction, 18.1cm/s in the bottom layer, 245 ° in the flow direction, and 10.3cm/s in the southern surface layer,The flow direction is 220 °, the bottom layer is 2.6cm/s, the flow direction is 181 °, the west surface layer is 23.8cm/s, the flow direction is 225 °, the bottom layer is 24.8cm/s, the flow direction is 198 °.
sea wave.Waves usually include waves and swells.The average and maximum wave height of the fishing ground is 0.5 m in April, 2.9 m in April, 0.5 m in May, 3.0 m in June, 0.5 m in June, 3.2 m in July, 0.6 m in July, 3.5 m in August, 0.5 m in August, 3.0 m in August, 0.5 m in September, 2.7 m in maximum, 0.5 m in October, 3.0 m in maximum, 0.5 m in November, and 2.4 m in maximum.
Sea ice.Sea ice is a unique natural phenomenon in northern China.The first ice day of the fishery is November 9 at the earliest, December 18 at the latest, November 23 on the average, March 8 at the earliest, April 4 at the latest, March 23 on the average, the minimum ice age is 99 days, the maximum ice age is 147 days, and the average ice age is 120 days.[2]
Seawater chemistry
pH。The seawater PH value of Donggang Fishing Ground is 8.14 in the surface layer, 7.85-8.36 in the variation range, 8.15 in the middle layer, 8.06-8.25 in the variation range, 8.15 in the bottom layer, and 8.01-8.23 in the variation range.The oceanic estuary is 8.10, and the PH value increases rapidly from Dalu Island to the southeast in tongue shape, between 8.20 and 8.36.
Water temperature.The average water temperature in the fishing ground is 23.66 ℃ in the surface layer, 22.4-25.12 ℃ in the middle layer, 21.98 ℃ in the middle layer, 21.5-22.3 ℃ in the middle layer, 21.40 ℃ in the bottom layer, and 20.8-24.1 ℃ in the range.
Dissolved oxygen.The average dissolved oxygen in the fishing ground is 7.78 micromol/cubic decimeter in the surface layer, with a variation range of 6.24-10.84 micromol/cubic decimeter in the middle layer, 8.49 micromol/cubic decimeter in the middle layer, 6.98-9.82 micromol/cubic decimeter in the bottom layer, 7.63 micromol/cubic decimeter in the bottom layer, and 6.66-9.12 micromol/cubic decimeter in the variation range.
Active phosphate.The average active phosphate in the fishing ground is 1.82 micromol/cubic decimeter in the surface layer, the concentration range is 0.25-1.63 micromol/cubic decimeter in the middle layer, 1.07 micromol/cubic decimeter in the middle layer, 0.25-1.83 micromol/cubic decimeter in the bottom layer, 1.24 micromol/cubic decimeter in the bottom layer, and the concentration range is 0.25-3.85 micromol/cubic decimeter.
Silicate.The average silicate in the fishing ground is 23.02 micromol/cubic decimeter in the surface layer, the concentration range is 1.92-49.90 micromol/cubic decimeter in the middle layer, 3.78 micromol/cubic decimeter in the middle layer, 0.57-9.6 micromol/cubic decimeter in the bottom layer, 8.15 micromol/cubic decimeter in the bottom layer, and 0.22-22.27 micromol/cubic decimeter in the concentration range.
Nitrite.The average nitrite in the fishing ground is 1.21 micromol/cubic decimeter in the surface layer, the concentration range is 0.24-3.06 micromol/cubic decimeter in the middle layer, 0.32 micromol/cubic decimeter in the middle layer, 0.13-0.83 micromol/cubic decimeter in the bottom layer, 0.57 micromol/cubic decimeter in the bottom layer, and 0.06-1.58 micromol/cubic decimeter in the concentration range.
Nitrate.The average nitrate in the fishing ground is 12.11 micromol/cubic decimeter in the surface layer, the concentration range is 0.59-19.96 micromol/cubic decimeter in the middle layer, 4.52 micromol/cubic decimeter in the middle layer, 0.32-7.59 micromol/cubic decimeter in the bottom layer, 6.5 micromol/cubic decimeter in the bottom layer, and the concentration range is 1.26-19.96 micromol/cubic decimeter.
Ammonia salt.The average ammonia salt in the fishing ground is 1.92 micromol/cubic decimeter in the surface layer, 0.00-6.35 micromol/cubic decimeter in the middle layer, 1.32 micromol/cubic decimeter in the middle layer, 0.28-2.66 micromol/cubic decimeter in the bottom layer, 1.35 micromol/cubic decimeter in the bottom layer, and 0.00-3.19 micromol/cubic decimeter in the concentration range.[2]
marine organism
Chlorophyll-a content.The total average value of chlorophyll a content in the northern Yellow Sea is 1.32 mg/m3, of which the highest content in Dalu Island is 4.78 mg/m3.
Primary productivity.Primary productivity refers to the production capacity of organic carbon or phytoplankton in the sea area.The total average value of primary productivity carbon in the northern Yellow Sea is 173.8 mg/m2/day.Among them, the daily average carbon production capacity of Dalu Island sea area is 595.74 mg/m2. day, and the annual average carbon is 217.45 mg/m2. day.
Phytoplankton.A total of 62 species of 30 genera of phytoplankton were collected from the northern Yellow Sea.Among them, 34 species were collected from the fishing ground, including 96.7% diatoms and 3.3% dinoflagellates. The dominant species of phytoplankton are Campanula floating, Chaetoceros rotundus and Chaetoceros spiralis.The average biomass of phytoplankton in the Yalu River estuary and Yuanshan fishing ground is the highest, reaching 2227.1 × 104 cells/m3, which is about 11 times higher than the comprehensive average value (185 × 104 cells/m3) of other areas in the northern Yellow Sea.
Zooplankton.A total of 61 species of 26 genera of zooplankton were collected from the northern Yellow Sea.Among them, 7900 are noctiluca.The dominant species of zooplankton is Daphnia minor.The average biomass of zooplankton in the Yalu River estuary and Yuanshan fishing ground is the highest, reaching 33437.5 cubic meters, about 5 times higher than the comprehensive average value of other areas in the northern Yellow Sea.
Benthos.The number of benthos in the northern Yellow Sea is 134, including 2 coelenterates, 10 polychaetes, 44 molluscs, 28 crustaceans, 25 echinoderms, 11 fishes, 3 algae and 11 others.The distribution of benthic biomass in the fishing ground is an average density of 0.13 per square meter, an average biomass of 3.9 grams per square meter, and a quantity index of 0.51.
The superior ecological and geographical conditions, vast sea resources and suitable climate provide an ideal natural environment for the survival and reproduction of Portunus sinensis in Donggang.[2]
Donggang Geography
historical origin
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Donggang Portunus sinensis is tender and delicious, and has been regarded as a good seafood since ancient times.
In the Tang Dynasty, the poet Bai Juyi wrote in "Twenty two Rhymes of Linghu Xianggong in Fenghe Bianzhou" that "Lu Zhen's bear paws are rotten, and seafood crab paws are formed", comparing crab paws with bear paws.
In the Qing Dynasty,Li YuIt is praised as "Crab is fresh and fat, sweet and greasy, white as jade and precious as gold, and has made the most of color, fragrance, and none of them can be matched".
Donggang Portunus has been highly concerned by local people since ancient times. The earliest Donggou County Annals (the original name of Donggang City) and Donggang Yearbook have records and descriptions of Donggang Portunus.
In the former Donggou County Fisheries Bureau's "Statistics of Donggou County Fisheries System", since 1953, Donggang Portunus sinensis has been recorded as the main fishery species.[4]
In the 1980s, the small island village of Donggang Bodhisattva Temple Town began to artificially breed swimming crabs.At that time, the breeding of seedlings was totally dependent on sea arrest and depended on the weather. Once the year was bad, the harvest would be poor.In normal years, the economic income of farmers is considerable and has formed one of the main industries in the region.
In 2005, with the support of Dandong City and Donggang City's aquatic scientific research departments, Bodhisattva Temple Town took the lead in carrying out the early artificial incubation test of Portunus sinensis seedlings, which was successful that year. The average weight of artificially bred Portunus sinensis reached 0.3 jin, and the individual weight reached 0.6 jin, ending the history of artificial breeding of Portunus sinensis in Dandong,It pioneered the early artificial incubation of swimming crab larvae.[5]
In 2010, Donggang Yellow Sea Water Products Industry Association began to organize relevant professional and technical personnel to carry out national geographical indication certification and national geographical indication certification trademark application for three aquatic products, namely, "Donggang Portunus", "Donggang Rhubarb Clam" and "Donggang Variegated Clam", which not only won the geographical indication certification for Donggang Portunus, Donggang Rhubarb Clam and Donggang Variegated Clam,At the same time, it also obtained the certification trademark of Donggang Portunus sinensis national geographical indication.[6]
Production
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In 2007, the breeding area of Portunus sinensis in Donggang increased by 4000 mu over the previous year, reaching 20000 mu.[7]
In 2009, Donggang exported more than 2500 tons of swimming crabs with a value of 20.76 million dollars.
In 2017, the total output of aquatic products in Donggang City was 462000 tons, the fishery output value was 5.68 billion yuan, and the total fishery economic output value was 10.825 billion yuan.[8]
In 2018, Donggang City has 500 frozen aquatic product processing enterprises, including 50 processing enterprises above designated size, 29 with export volume of more than US $5 million, 13 with export volume of more than US $10 million and 3 with export volume of more than US $20 million.The annual processing volume of aquatic products in the city is 400000 tons, and the export value is 525 million dollars. The main varieties processed are shellfish, squid, mackerel and Spanish mackerel, sea crucian carp, swimming crab, etc.[9]
Product honor
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On September 13, 2011, the Ministry of Agriculture of the People's Republic of China approved the registration and protection of geographical indications of agricultural products for "Donggang Portunus".[1-2]
Portunus donggang
geographical indication
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Scope of geographical protection
Donggang Portunus sinensis is mainly produced in the Yalu River estuary fishery and Yuanshan fishery in the north of the Yellow Sea.The scope of regional protection includes 18 fishing areas, 19 fishing areas, communities 2, 3 and 6 of 32 fishing areas and 33 fishing areas.The geographical coordinates are 39 ° 47 ′ 04 ″ north latitude, 123 ° 30 ′ 57 ″ east longitude, 124 ° 00 ′ 00 ″ north latitude and 39 ° 00 ′ 00 ″ east longitude. The northern boundary is along the land, and the eastern and southern boundaries are on the Chinese side of the Sino Korean maritime boundary, with a total area of about 3500 square kilometers.[2]
Quality and technical requirements
(1) Origin selection and requirements
The place of origin is Yalu River Estuary Fishing Ground and Yuanshan Fishing Ground at the northernmost end of the fishing ground in the northern Yellow Sea.The fishing ground is close to the land area of Donggang City. The average distance from the fishing port to the operation area of the fishing ground is about 80 kilometers. General motor-driven fishing boats can arrive on the same day and return to the port the next day, which is conducive to production, to improving the temporary survival rate of Portunus sinensis in Donggang, and to increasing the added value of products.
The main indicator of origin requirements is the marine environment (quality) standard of fishing grounds, which must comply with the Sea Water Quality Standard GB3097-1997, that is, Class I sea water quality of sea water quality standard, marine sediment standard and marine organism residual toxicity standard, which is applicable to marine fishery waters, marine nature reserves and rare and endangered marine organism reserves.Over the years, the water quality of the Yalu River Estuary Fishing Ground and Yuanshan Fishing Ground has been maintained as Class I seawater, which fully meets the living conditions of Portunus sinensis in Donggang and meets the national quality requirements for pollution-free agricultural products.
(2) Variety definition
Donggang Portunus trituberculatus is a wild Portunus trituberculatus caught by Yalu River Estuary Fishing Ground and Yuanshan Fishing Ground.Biological characteristics of Portunus donggang.The cephalothorax is fusiform and slightly elevated.There are three prominent warty protuberances on the surface, one in the stomach area and two in the heart area.Its shape is oval, and its two ends are as sharp as cloth shuttles, so it is called Donggang Portunus.The two front lateral edges each have 9 serrations, and the 9th serration is particularly long and extends to the left and right.There are 4 small teeth on the frontal margin.There is a pair of compound eyes with handles that can rotate on both sides of the forehead.There are 5 pairs of chest feet.The chelopods are developed, with long prismatic nodes and blunt teeth on the inner edge.The fourth pair of feet are flat, wide and thin as oars, suitable for swimming.The abdomen is flat, the male crab's abdomen is triangular, and the female crab's abdomen is round.The male crab has a tea green back, the female crab is purple, and the abdomen is gray white.
(3) Fishing season
Donggang Portunus sinensis can be caught during the rest of the year, except the closed season for breeding and protection in the summer from 12 o'clock on June 16 to 12 o'clock on September 1 every year.
(4) Fishing specifications
According to the Detailed Rules for the Implementation of the Protection of Aquatic Resources in Liaoning Province issued by the People's Government of Liaoning Province in 2008 (revised), it is prohibited to catch the young Portunus donggang crab whose vertical distance from the center of the head breastplate to the posterior edge of the nail is less than 7cm.The vertical distance from the center of the head breastplate to the rear edge of the nail is more than 7cm, and those reaching the standard of adult crabs can be caught.
(5) Fishing boats and fishermen
Fishing vessels must be seaworthy fishing vessels with complete three certificates, namely, the Registration Certificate of Fishing Vessels of the People's Republic of China, the Inspection Certificate of Fishing Vessels of the People's Republic of China and the Fishing License Certificate of the People's Republic of China.Fishing vessels shall be equipped with communication, navigation, signal, fire fighting, life-saving and other equipment and facilities as required.Waste oil and non degradable waste storage equipment shall be provided.Fishermen should obtain the Certificate of Duty Crew and the Certificate of Seafarer issued by the relevant departments, which are consistent with the class of the fishing boat they are driving and the position they are engaged in.
Marine fishing vessels do not have special nets for catching Portunus sinensis in Donggang, but they are commonly used side catch nets, mainly including swimming nets and fixed nets.Swimming nets also include trawls and gillnets.Trawling is to use a powered fishing boat to drag a trawl with one bag and two wings or only a bag net, move on the seabed, and collect fish, shrimp and crab bodies into the bag.The trawl includes wing trawl, wingless trawl, ground trawl, raking net, etc.Another type of swimming net is gill net.The gill net is a long belt type, and the mesh is determined by the main fishing objects, ranging from 20 to 330 mm. Each piece of net is 1 to 6 meters high and 50 to 150 meters long. The upper and lower edges of the net are generally filled with floaters, sinkers and floaters.During operation, connect dozens to hundreds of nets, put them into the water to form a wall, cut off the access of the fish, and make the fish bones hang on the mesh or wind on the net clothes.The gill net includes flowing gill net, surrounding gill net, dragging gill net, etc.Fixed nets include anglerfish net, pile net, mast net, boat net, leak net, etc.
The mesh size of fishing nets shall be restricted. If the minimum mesh size of aircraft boat trawl, purse seine and motorboat trawl is operated in the Yellow Sea, the mesh size of the purse seine used by trawlers with power below 110kw shall not be less than 50mm;The bag mesh of trawl used by trawlers with power above 110kw shall not be less than 54mm.
(7) Production process and operation
In the fishing operation of the fishing ground, the Donggang Portunus sinensis caught by fishing vessels shall be sorted and repackaged in a timely manner, and the selection shall first determine whether to temporarily raise live crabs or to market dead crabs.The temporary rearing of Portunus donggang with live crabs should be carried out according to the temporary rearing technology.Donggang Portunus sinensis, which is listed as dead crab, should be washed with seawater first, then graded according to the specification, male and female, and then put into plastic screens (baskets) in a fixed amount, and then put into machine made artificial ice for storage at a ratio of 10:1.
(8) Temporary maintenance
Techniques for fishing boats to temporarily raise portunus sinensis in Donggang. ①It is necessary to select the caught Portunus donggang, and select the Portunus donggang with consistent individuals, sound limbs, no trauma, and strong mobility for temporary rearing. ②That is, seawater can be used for cleaning. ③Bundle, use flexible rubber band to fasten the claw feet of Portunus donggang. ④Cage loading, the stacking of Donggang Portunus sinensis in the cage shall not exceed 2 layers at most, and the cage shall be sealed with nets. ⑤Barrel filling (both water tank and water tank are available, and the drum is the best). After the crab cage is filled into the barrel, at least 30cm water level shall be reserved. ⑥Cool down.The bucket shall be filled with filtered clean seawater. Before being filled with Portunus donggang, the seawater in the bucket shall be cooled with machine-made artificial ice, and the temperature shall be reduced to 8-12 ℃.
Use the formula of ice precipitation temperature and ice volume (ton).Where, m2=water consumption (ton), m1=water to be cooled (ton), t1=water temperature to be cooled (℃), t2=water temperature to be cooled (℃). ⑦inflation.After entering the cage, Donggang Portunus sinensis shall be continuously inflated, and the inflation port shall be evenly distributed at the bottom of the barrel. ⑧Shading.The bucket filled with portunus sinensis in Donggang shall be shaded or stored in the cabin for as short a time as possible to ensure the survival rate of temporary rearing.[2]
