A method to increase the proportion of migratory individuals in the first generation of Marsu salmon roe.

Abstract

This invention discloses a method for increasing the proportion of migratory individuals in the first generation of salmon roe. The method is characterized by the following steps: First, in January, mature landlocked salmon broodstock are induced to spawn. After the eggs hatch into fry and begin feeding, the fry are placed in a flowing-water rearing pond for two months, with a population density of 200-300 fry / m². 3 The culture water temperature is 6-8℃, dissolved oxygen is 8-10 mg / L, and the fish are fed artificial feed twice a day, with each feeding amount being 2% of the wet weight of the fry. After completing the first stage of cultivation, at the end of March, juvenile fish with a body length of 2-3 cm and a weight of 1±0.2 g are selected and cultured in flowing water for 3-4 months, with a population density of 8000-10000 fish / m³. 3 The water temperature for rearing is 8-10℃, the dissolved oxygen is 8-10 mg / L, and artificial compound feed is given twice a day, with each feeding amount being 0.2% of the wet weight of the fry.

Description

Technical Field

[0001] This invention relates to the field of aquaculture, and in particular to a method for increasing the proportion of migratory individuals in the first generation of salmon roe. Background Technology

[0002] Masson salmon ( Oncorhynchus mass The Masu salmon is mainly distributed in the Tumen River, Heilongjiang River, and Suifen River basins. Historically, it was one of the unique economic fish species in northern my country, with an annual catch of up to 500,000 tons. However, due to habitat loss caused by human activities, uncontrolled fishing, and insufficient stock enhancement resources, the natural population of Masu salmon is on the verge of extinction. The total annual migration of all river basins in China is less than 10,000 individuals, and its distribution area is narrow, with a landlocked population preserved only in the Mijiang River in Jilin Province. It is now listed as a national second-class protected animal.

[0003] The salmon (Chum salmon) is a migratory fish. During their freshwater life, its juveniles differentiate into two life history types: migratory and landlocked populations. The migratory population migrates to the ocean to complete its development and growth, returning to its birthplace river after 4-5 years to repeat the life history process. Resource conservation and species protection of the salmon primarily rely on releasing migratory populations, and using mature migratory salmon to cultivate and release a new generation of fry. However, the number of migratory broodstock individuals currently available in my country is extremely limited, insufficient to meet the needs of stock enhancement. Therefore, using artificially bred landlocked salmon for breeding and release is an effective method to address the current shortage of migratory salmon broodstock resources. However, the proportion of migratory individuals in the offspring of landlocked salmon is usually 20-30%. Therefore, increasing the proportion of migratory individuals in the offspring of landlocked salmon and meeting the requirements for stock enhancement and release will greatly promote the recovery of salmon fishery resources and the protection of this species in my country. Summary of the Invention

[0004] The present invention aims to solve the above-mentioned technical problems by proposing a method for breeding masu salmon that can significantly increase the proportion of migratory individuals in the first generation.

[0005] The technical solution of this invention is: a method for increasing the proportion of migratory individuals in the first generation of salmon roe, characterized in that: the method is performed sequentially according to the following steps:

[0006] First, in January, mature landlocked chum salmon parent fish are induced to spawn. After the eggs hatch into fry and begin feeding, the fry are placed in flowing water rearing ponds for two months, with a population density of 200-300 fish / m² during this period. 3The culture water temperature should be 6-8℃, dissolved oxygen 8-10 mg / L, and the fish should be fed artificial formulated feed twice a day, with each feeding amount being 2% of the wet weight of the fry.

[0007] After completing the first stage of cultivation, at the end of March, select juvenile fish with a body length of 2-3 cm and a weight of 1±0.2 g. These juveniles will then be cultured in flowing water for 3-4 months, with a population density of 8000-10000 fish / m³. 3 The water temperature for rearing is 8-10℃, dissolved oxygen is 8-10 mg / L, and the fish are fed artificial formulated feed twice a day, with each feeding amount being 0.2% of the wet weight of the fish fry.

[0008] Alternatively, after completing the first stage of cultivation described above, the juvenile fish can be cultured in a recirculating aquaculture system for 3-4 months, with a daily water exchange rate of 20-30% and a stock density of 2000-3000 fish / m² during the rearing period. 3 The water temperature for rearing is 8-10℃, dissolved oxygen is 8-10 mg / L, and artificial compound feed is given twice a day, with each feeding amount being 0.2% of the wet weight of the fry.

[0009] In the later stages of the second phase of cultivation, around mid-July, the first-generation juveniles of the Masu salmon began to differentiate into either landlocked or migratory individuals, with migratory individuals accounting for 70-80%.

[0010] Compared with the prior art, the present invention has the following advantages:

[0011] The method for cultivating salmon and tilapia described in this invention is simple to operate and the relevant conditions are easy to implement. Compared with traditional breeding or cultivation methods, its main difference lies in the fact that after the larval stage, when cultivating juvenile fish, the stocking density is significantly increased, while the daily feeding amount is also significantly reduced. This intensifies the competitive pressure for food and living space among individuals within the population, prompting individuals to secrete large amounts of cortisol, thyroid hormones, and growth hormones. This induces individuals to migrate to the sea to find food and living space, thereby greatly increasing the rate of differentiation of the first-generation juvenile fish into migratory individuals, reaching 70-80%. This significantly improves the efficiency of artificial propagation and release of salmon and tilapia. Detailed Implementation

[0012] The specific embodiments of the present invention will be described below.

[0013] A method for increasing the proportion of migratory individuals in the first generation of masu salmon roe is performed by following these steps:

[0014] First, in January, mature landlocked chum salmon parent fish are induced to spawn. After the eggs hatch into fry and begin feeding, the fry are placed in flowing water rearing ponds for two months, with a population density of 200-300 fish / m² during this period. 3 The water temperature for cultivation is 6-8℃, the dissolved oxygen is 8-10 mg / L, and artificial compound feed is given twice a day. Each feeding is 2% of the wet weight of the fry. This process is the first stage of cultivation.

[0015] After completing the first stage of cultivation, at the end of March, select juvenile fish with a body length of 2-3 cm and a weight of 1±0.2 g. These juveniles will then be cultured in flowing water for 3-4 months, with a population density of 8000-10000 fish / m³. 3 The water temperature for rearing is 8-10℃, dissolved oxygen is 8-10 mg / L, and the fish are fed artificial formulated feed twice a day, with each feeding amount being 0.2% of the wet weight of the fish fry.

[0016] Alternatively, after completing the first stage of cultivation described above, the juvenile fish can be cultured in a recirculating aquaculture system for 3-4 months, with a daily water exchange rate of 20-30% and a stock density of 2000-3000 fish / m² during the rearing period. 3 The water temperature for rearing is 8-10℃, dissolved oxygen is 8-10 mg / L, and artificial compound feed is given twice a day, with each feeding amount being 0.2% of the wet weight of the fry.

[0017] In mid-July, during the later stages of the second phase of rearing, the first-generation juveniles of the Masu salmon roe begin to differentiate into either landlocked or migratory individuals, with migratory individuals accounting for 70-80%. To determine whether a juvenile is migratory, observe the black spots on both sides of the fish's body. If the color of the black spots becomes significantly lighter, it indicates that the individual is migratory. Specific Implementation

[0018] On January 10, 2023, newly hatched fry of the marsucho salmon were placed in a 2m deep pool. 3 Freshwater flowing water culture was carried out in rectangular culture ponds, with a population density of 250 fish / m². 3 The culture water temperature is 6℃, the dissolved oxygen is 8.5mg / L, and the fish are fed artificial compound feed twice a day, with each feeding amount being 2% of the wet weight of the fry.

[0019] On March 20, 2023, juvenile fish measuring 2.5cm in length and 1.1g in weight were selected and cultured in a 100L tub-shaped tank using a recirculating aquaculture system. The daily freshwater exchange rate of the recirculating aquaculture system was 20%, and the stock density during the culture period was 2500 fish / m². 3The culture water temperature was 10℃, dissolved oxygen was 9.0 mg / L, and the fish were fed artificial formulated feed twice a day, with each feeding amount being 0.2% of the wet weight of the fish fry. This was the culture experimental group.

[0020] On March 20, 2023, juvenile fish measuring 2.5 cm in length and 1.1 g in weight were selected and cultured in a 100L tub-shaped tank using a recirculating aquaculture system. The daily freshwater exchange rate of the recirculating aquaculture system was 20%, and the stock density during the culture period was 250 fish / m². 3 The culture water temperature was 10℃, dissolved oxygen was 9.0 mg / L, and the fish were fed artificial formulated feed twice a day, with each feeding amount being 2% of the wet weight of the fish fry. This was the culture control group.

[0021] From July 10th to 20th, 2023, the first-generation juveniles of Masu salmon roe began to differentiate into either landlocked or migratory individuals. The criterion for identifying migratory individuals was a significant lightening of the color of the black spots on the sides of the fish's body. Statistical data showed that migratory individuals accounted for 77.5% in the experimental group, compared to 31.4% in the control group. The proportion of migratory individuals in the experimental group was significantly higher than that in the control group.

Claims

1. A method for increasing the proportion of migratory individuals in the first generation of salmon roe, characterized in that: The method is performed in the following steps: First, in January, mature landlocked chum salmon parent fish are induced to spawn. After the eggs hatch into fry and begin feeding, the fry are placed in flowing water rearing ponds for two months, with a population density of 200-300 fish / m² during this period. 3 The culture water temperature should be 6-8℃, dissolved oxygen 8-10 mg / L, and the fish should be fed artificial formulated feed twice a day, with each feeding amount being 2% of the wet weight of the fry. After completing the first stage of cultivation, at the end of March, select juvenile fish with a body length of 2-3 cm and a weight of 1±0.2 g. These juveniles will then be cultured in flowing water for 3-4 months, with a population density of 8000-10000 fish / m³. 3 The water temperature for rearing is 8-10℃, dissolved oxygen is 8-10 mg / L, and the fish are fed artificial formulated feed twice a day, with each feeding amount being 0.2% of the wet weight of the fish fry. Alternatively, after completing the first stage of cultivation described above, the juvenile fish can be cultured in a recirculating aquaculture system for 3-4 months, with a daily water exchange rate of 20-30% and a stock density of 2000-3000 fish / m² during the rearing period. 3 The water temperature for rearing is 8-10℃, dissolved oxygen is 8-10 mg / L, and the fish are fed artificial formulated feed twice a day, with each feeding amount being 0.2% of the wet weight of the fish fry. In the later stages of the second phase of cultivation, around mid-July, the first-generation juveniles of the Masu salmon began to differentiate into either landlocked or migratory individuals, with migratory individuals accounting for 70-80%.