A brief analysis of the culture technology of small cages of greenfin horse-faced pufferfish seed in Haizhou Bay
Text/ Zhu Xibo
Haizhou Bay is located at the intersection of the coastal main axis of the national key development and the economic belt along the new Eurasian Land Bridge, the combination of the Bohai Rim Economic Circle and the Yangtze River Delta Economic Circle, and is an important part of the Oriental Bridgehead of the Eurasian Land Bridge. In recent years, the lack of resources, the fishing industry due to the adjustment of the national fuel subsidy policy is facing a severe test; land and other industrial development, to the entire factory aquaculture industry has brought an impact, the scale of aquaculture has dropped sharply, the factory aquaculture industry passive compression; shallow sea raft culture to low-value shellfish as the mainstay, single breeding species, market price fluctuations are larger, high risk, in recent years due to changes in seawater water quality and germplasm degradation and other reasons, shellfish farming is hindered, urgently need to explore new seawater breeding.
At the time when the country is vigorously developing the marine industry, Shandong Province has comprehensively promoted the construction of "sea granary", the development of seawater anti-wind cage culture and other facilities fishery has a lot of room for development, seawater cage aquaculture industry can be expanded from offshore waters to deep waters, which can reduce the pressure of shallow sea, harbor and beach aquaculture, give full play to blue land resources to provide a broader space for the marine aquaculture industry, which is conducive to the adjustment of industrial structure and the transformation of fishermen; its high yield, high efficiency, large capacity, The environmentally friendly breeding mode makes the marine aquaculture industry develop in the direction of scale, intensification and industrialization, which is conducive to achieving the strategic goal of marine agriculture and animal husbandry; the sea area is open, the water body is convenient, it is conducive to the protection of the ecological environment, the reduction of pollution caused by marine aquaculture itself, the improvement of the quality of commercial fish products, and the reduction of breeding diseases.
The greenfin pufferfish belong to the class of teleost fish, the monocornal puffer family, commonly known as rubber fish, peeling fish, mouse fish, pig fish, cobbler fish. It is distributed in Korea, Japan, the east coast of Africa in the Indian Ocean, and the East China Sea, the Yellow Sea, the Bohai Sea, and Shanghai, and is found in the Yangtze River estuary and other seas, and belongs to the offshore demersal fish. It often inhabits water depths of 50m to 120m. The fins are dark green, and the second dorsal, pectoral and fins are all green, hence the name. Its meat taste is delicious, high fat content, rich nutrition and rapid growth, high economic value, is China's excellent economic marine fish. Once the green-tipped horsefish were the runner-up in sea fishing, Haizhou Bay was one of its main spawning grounds, and the spawning period was from May to June. Since the 1990s, fishing has declined sharply due to overfishing and other reasons, with production of only 0.2 million tonnes in 1995 and a significant decline in natural resources.
Fig. 1 Greenfin horse-faced pufferfish
In recent years, the greenfin pufferfish has rarely been seen on the market, and the market price has been rising. Live fish over 400g are priced at more than 150 yuan per kilogram in Qingdao, Shenzhen and Guangzhou markets, while chilled fish from 250g to 300g are in short supply as high-grade Japanese fish materials in coastal cities. In order to enrich the resources of greenfin horse-faced pufferfish, the author explored the cultivation of green-fin horse-faced pufferfish in seawater cages, and the test proved that in Haizhou Bay, the large-scale seawater cage culture of greenfin horse-faced pufferfish was successfully carried out.
1. Materials and methods
(1) Experimental fish sources
The greenfin horse-faced pufferfish seed used in the experiment was provided by the fish team of the Yellow Sea Fisheries Research Institute of the Chinese Academy of Fisheries, and all the greenfin horse-faced puffer fry in the experiment came from healthy juveniles hatched from the same fertilized eggs.
(2) Experimental settings
Samples of greenfin horsefish seed: Two cages were randomly selected as two treatment groups, and the seed of each treatment group was sampled, and 20 individual weights and weights were randomly collected from each group.
The trial began at the end of May 2019 and all fry were cultured in cages from the end of May to the beginning of July 2019. Fry once between 8 cm and 10 cm in size.
(3) Test conditions
The cage location is the breeding base of The Lanshan Branch of Rizhao Aquatic Products Group in the north of Haizhou Bay, and the water quality of the aquaculture sea area is pollution-free, and the overall quality of the sea area is better, which meets the national first-class seawater quality standards. The culture cage is a square cage with a cage size of 5 m×5 m (length× width) and a depth of 3 m.
Fry mesh is 0.8cm-2 cm (including 0.8cm-1.0 cm before seeding and 1.5 cm-2.0 cm after seedling separation), the maximum aquaculture water volume of a single cage is 75 m3, and the effective water volume is 65 m3. During the test period, the water temperature of the test waters was 20 °C ~ 29 °C.
(4) Feed feeding
The feed used for the greenfin pufferfish is a compound feed and shrimp skin, and the feeding amount is determined according to the size of the fry and the water temperature. See Table 1 for details.
Table 1 Comparison table of feeding times
2. Aquaculture production management
(1) Water temperature and water quality indicators
The annual average surface sea temperature in Haizhou Bay is 14.4 °C. The annual average surface water temperature is the highest 17.4 °C and the lowest is 13.0 °C. March to August is the warming period, with april to July being the best, with an average rate of 4.8°C/month, and July to September being the highest average water temperature season, with August having the highest surface water temperature at 26.5°C. September to December is the cooling period, with October to December cooling the fastest, January and February as the monthly average minimum temperature months, of which February has the lowest water temperature of 2.9 °C. The optimal water temperature for the cultivation of greenfin horsefish seed was 20 °C to 26 °C, and the experimental selection was carried out in small cage culture in Haizhou Bay from May to July. It has a wide adaptability to salinity, and can grow rapidly in seawater with salinity of 25 to 32. Water temperature, bait feeding, fish deaths and weather conditions are recorded at regular intervals (7:00, 18:00) during the farming period.
(2) Seedlings
1. Fish body: Stocking fry requires the fish body to be complete, the body surface is smooth and free of lesions, the color is normal, the system is robust and vigorous, and there is no injury, no insects and no disease.
2. Specifications: Stocking seedlings have a size of 3cm to 5cm, and the specifications are neat.
3. Quarantine: When purchasing seedlings from different places, quarantine should be carried out to strictly prevent the spread of pathogens in different places.
4. Transportation: Stop eating for 2 days before the transport of seedlings, control the temperature difference between the water temperature and temperature of long-distance transportation within 5 ° C, and adjust the water temperature during transportation at about 18 ° C.
5. Seed stocking: Choose the water temperature at about 22 ° C for stocking, and do a good job of protective measures to prevent fish fry from being injured and ensure the survival rate.
(3) Breeding density
See Table 2 for details.
Table 2 Culture density of different types of fry
III. Conclusion
Experiments have proved that the cage culture of greenfin horse-faced pufferfish in Haizhou Bay is successful. The fastest growth rate of greenfin horsefish in the cage of Haizhou Bay is from May to July, of which the best growth around the middle of June, the best water temperature for growth is between 20 °C and 26 °C, and the green fin horse face puffer does not have high salinity requirements and can tolerate salinity range.
Seed quality and seed size directly affect the survival rate of culture. The selection of suitably sized, injury- and disease-free greenfin horse-faced pufferfish seed for small cage culture is key to improving survival. Small-sized seedlings (3 cm to 5 cm) had the largest average daily growth in the suitable water temperature environment between May and July in Haizhou Bay. After the body length reaches a large size (11 cm to 14 cm), it can be considered to be stocked into a large cage for growing. It can also take the form of land-sea relay, take the combination of factory circulating aquaculture and marine cage culture, reduce the cost and energy consumption of aquaculture, shorten the breeding cycle, and increase production, so as to achieve the purpose of improving economic benefits. From the current point of view, the cage culture of greenfin horse-faced pufferfish in Haizhou Bay is a breeding model worth promoting.