Artificial breeding and stocking operation technology of spotted amberjack in Zhejiang Province
_ Single Lezhou
Clupanodon punctatus (Clupanodon punctatus) is distributed in the coastal areas of China, is a typical coastal harbor fish in the East China Sea, its food nutrition level is low, mainly phytoplankton and zooplankton for food, but also feeds on organic detritus and benthic diatoms, is a phytoplankton-based filter feeding fish, known as the "white carp" in the seawater. Most of the fish species artificially released by domestic seawater are high-trophic carnivorous varieties, and the fish species lack low-nutrient level plant-feeding and filter-feeding fish species. Spotted dumplings have unique feeding habits, which are rare in seawater with both ecological clean water function and fishermen's fishing and income increase economic benefits, which can play an important function and role in fishery resources and environmental restoration and ecological fishery, and it is waiting for us to pay attention to and carry out the research and application of artificial breeding and breeding and stocking technology of spotted dumplings.
Since 2017, the fish research team of Zhejiang Marine Aquaculture Research Institute has carried out large-scale artificial breeding and breeding and stocking of spotted dumplings every year, accumulating a lot of practical work experience. Spotted fish fry are irritable, the scales are easy to fall off, and the collection, packaging, transportation and counting methods of artificial fry are difficult to operate and have a high mortality rate compared with most other marine fish. The fish research team of Zhejiang Marine Aquaculture Research Institute has solved the collection, packaging, transportation and counting methods of different day-old spotted fish fry under the artificial nursery mode of cement pond according to the habit of spotted amberjack artificial fry, and proposed the minimum specification standard for the breeding and stocking of spotted tender bread fry, which is summarized as follows, which can provide a reference for the artificial breeding and stocking of canned lopside in China.
1 In the process of large-scale seedling rearing of spotted catfish pond, with the change of habits at different stages of growth and development of fish fry, the tests and improvements of seedling collection, packaging, transportation and counting are continuously carried out, and the methods of fry collection, packaging, transportation and counting of fry of different days of age are summarized as follows.
1.1 Fry 20-30 days old
After 20 days, the phototropism begins to appear, the fry is 20-30 days old, the full length range is 1.6 to 2.0 cm, and the phototropism of the fry can be used for fry collection and packaging transportation, called the phototropism method, the specific method steps are as follows.
In the dark at night, first use a strong light flashlight to illuminate the nursery pond, a few minutes can gather to a lot of fry to the flashlight, and then switch to a weak light small flashlight, such as the number of fry in the nursery pond, you can directly use a weak light small flashlight, a large number of fry light gathered to the surface of the water, directly with a 1L spoon in the water with water to fish fry, and gently pour into the nylon fry bag oxygen packaging, fish fry bag size of 50 cm×90 cm, filled with water about 6 kg, filled with fry 3 000 ~ 5 000 tails, water temperature 20 ~ 22 °C, transport 6 h , the survival rate is more than 80%. In the process of scooping fry and pouring into nylon bags, and in the process of transporting nylon bags, there will be a small part of the fry frightened, the body from transparent to white and dead, even if the number of seedlings is very small, the transportation time is very short, there will still be more than 10% of the fry frightened and white death, the specific mortality rate and seedling collection, packaging, transportation during the operation of the action is related, the action is gentle about 10% death, on the contrary, the case fatality rate is as high as 20% to 50%.
There is no good way to count 20-30 day-old fry, and you can only estimate the number of nylon bag fry based on empirical visual density, or the number of tail points. Fry have a strong stress response at this day-old stage, and it is not recommended to collect, pack and transport fry at 20-30 days of age. The test also found that after the siphon siphon fry sub-pond was adopted, it was found that the siphon fry also had more deaths, and it was not suitable for siphon sub-pond, and the fry sub-pond could be directly poured into another pool by using the phototropic belt water fishing.
1.2 Fry 30-35 days old
Fry are 30-35 days old, the total length of the fry is 2.0 to 2.2 cm, and the seedling collection method can also be used by the phototropic belt water method. The size of the fry bag is 50 cm×90 cm, about 6 L of water, 2 000 to 3 000 fry, the water temperature is 20 ~ 22 °C, the transport is 6 h, and the survival rate is more than 95%. At this stage, the phenomenon of stress response and death of fry has been significantly reduced compared with the previous stage. Estimate the fry density and number of nylon bag fish by experience, or the number of tail points.
1.3 Fry 35-50 days old
Fry 35-50 days old, the total length of the fry is 2.2 to 3.1 cm, the fry also has a strong phototropism, the individual is obviously thick, due to the fry activity escape ability is also significantly enhanced, the number of fry fish fished with water in the water spoon is getting smaller and smaller, and it is gradually no longer suitable to use the above phototropic belt water method to collect seedlings.
Fry at this stage have been able to gather for feeding, and fry no longer have a whitish death similar to the previous stage of stress. Using the net method to collect seedlings, the specific method steps are: after the fry stop feeding feed for more than 4 h, choose to feed a small amount in the corner of the nursery pond, the fry will immediately gather on the surface of the nursery pond for feeding, with a diameter of 50 cm, handle 70 cm shallow bottom 56 mesh fishing net with water fishing, large fishing net slowly from the bottom up, fish fry gathered at the bottom of the net, large fishing net can not be completely separated from the water, and then use a short 21 cm diameter of aquatic products special water scoop in the fishing net with water fishing, poured into the fry bag, the size of the fish fry bag is 50×90 cm, About 6 kg of water, 1 000 to 3 000 fry, water temperature 22 ~ 25 °C, transport for 6 h, survival rate of more than 98%. Estimate the fry density and number of nylon bag fish by experience, or the number of tail points.
1.4 Fry 50-60 days old
Fry are 50-60 days old, the total length of the fry is 3.1 to 3.8 cm, and the surface of the fish has gradually grown scales. The fry begins to grow in a pronounced length and width, developing from an elongated shape to a lateral flattened shape.
Seedling collection method changed to a diameter of 40 ~ 50 cm of drainage round plastic basket, can be operated away from the water, referred to as the plastic basket method, the specific method steps are: fry stop feeding after more than 4 h, choose a small amount of feeding in the corner of the nursery pond, the fry will immediately gather to feed, a plurality of drainage round plastic baskets in turn fishing, and floating on the surface, a batch of plastic baskets after the collection of fish began to pack, packaging when the plastic basket away from the water, quickly poured into the filled water fry bag, the size of the fry bag is 50 cm×90 cm, the water is about 6 L, the fry 500 ~ 1 500 tails, water temperature 22 ~ 25 °C, transport 6 h, survival rate of more than 99%. Since the plastic basket floats on the surface of the water after fishing, and the fry can be added or decreased, the number of fry can be counted one basket by one by the tail point or weighed, and the remaining baskets can be visually measured with reference density, which can be relatively accurately counted.
1.5 Fry after 60 days of age
After the fry is 60 days old, the total length is more than 3.8 cm, the fry has been fully scaled, the spots on the side of the body have appeared faintly, resembling adult fish, the fry can be fished out of the water and weighed, the fry body surface will have a small number of scales falling, but does not affect the survival rate of the fry, the fry can re-grow scales. Fish can also be collected by the plastic basket method, the size of 50×90 cm of fry bags filled with water about 6 L, filled with 300 to 800 fry, water temperature 22 ~ 26 °C, transport 6 h, survival rate of more than 99%.
Spotted dumplings in April began to breed, after 60 days of age, the time will be 6-7 months later, the temperature and water temperature is high, when the water temperature is above 27 °C, the fish fry bag is filled with oxygen packaging, it is easy to lack oxygen, and the foam box is placed in an ice bag to keep the water temperature of the fry bag below 27 °C. Fry total length of more than 4 cm, a large number of fry collection can also be used at the bottom of the fry pond faucet all released fry, fry from the water weighing count, can be 100 L volume of the bucket 30 kg of water, filled with pure oxygen transport, filled with fry 2 kg, about 4,000 tails, water temperature 27 ~ 29 °C, transport 5 h, survival rate of more than 99%. Fry are over 4 cm long and can also be transported using conventional open bucket inflation. 1 t the water body in a drum of 700 kg of water, can hold a total length of more than 4 cm fry 10 kg, about 20,000 fish, water temperature 27 ~ 29 °C, transport 5 h, survival rate of more than 99%.
2 Minimum size and stocking pattern of stocking fry in spotted amberjack breeding
2.1 Minimum size of stocked fry in the breeding and stocking of spotted plover
The appropriate specifications of the breeding and stocking of spotted catfish fry are considered from the following aspects: first, the fry can adapt to the natural marine environment after being released, and can feed and grow in the natural marine environment; second, the fry counting and transportation are relatively convenient; and the third is the production and transportation cost of fry. At present, most marine fish stocking fry size is full length or body length of 5 cm, spotted amberjack is small and medium-sized fish, generally mature individual mass of about 50 g. According to the comprehensive consideration of the fry growth and living habits of different day-old fry of the spotted fish, and the comprehensive consideration of the fry collection, packaging, transportation and counting methods, it is believed that after the 55 days of age, the total length of the spotted fish fry is more than 3.5 cm, and the average total length is 3.8 cm, which is the smallest specification that can be artificially released. Of course, fry can also be reared to an individual of 4 to 5 cm or more in total length and then released.
2.1 Direct transport and release mode of fish fry in cement nursery ponds of nursery farms
It is recommended that after 55 days of age, the total length of the tender fry is more than 3.5 cm, the average total length is 3.8 cm, the plastic basket method collects fish, the fry can be counted by sampling weight method, and the small batch of fry transport can be transported by the fry bag oxygenated, the size of 50×90 cm is about 6 L of water in a fry bag, the average length of 3.8 cm fry is 500 to 1 000 fish, the water temperature is 22 to 26 °C, the transport is 6 h, and the survival rate is more than 99%. Bulk fry transport is recommended for inflated transport in open fish drums. Water temperatures above 27 °C must be transported in open fish drums. 1 t Drum fillets of water body 10 kg, water temperature 27 ~ 29 °C, transport for 5 h, survival rate of more than 99%.
2.2 On-site direct release mode after intermediate breeding of cages in the sea area
Spotted fish fry are directly released in the sea area after being reared in the middle of cages in the sea area, and their fry production costs are low and the survival rate after stocking is high, which is the preferred mode for the breeding and stocking of spotted fish. After the fry are 35 days old, the total length of the fry is more than 2.2 cm, and the fry is collected by the net method, and the fry bag is oxygenated and transported to the middle of the cage in the sea area for cultivation, and the fry is small, so it can be transported at a relatively high density. After sea cage rearing to an average total fry length of 3.8 cm or larger, fry can be weighed and counted by weight sampling and released directly at the cage rearing site.