(a) Fish? e farming
Fish-e farming is the use of coastal harbors, estuaries, coastal tidal flats or low-lying areas, added to artificial embankments, ditching gates, storage of seawater, the introduction of natural fry or artificial seedlings for breeding through tides. .
1. Venue selection
Bays built with strong bays should be used to build fish because of the small waves in the inner bays or tidal flats on both banks of the river and not affected by floods. It's best to build in the port of Hong Kong. The location is required to be on the mid-tide line. The terrain is relatively flat and has a certain degree of inclination. It is easy to drain water and raise seedlings. The location is too low or too high is not conducive to production and construction. It is required to choose the sediment quality. The area of ​​this type of sediment is more fertile, which is conducive to the biological reproduction of the bait, and the embankment is strong and has strong water retention. The seawater of the fish?e is incorporated with the tide, requiring a relatively clean water quality, a certain fertility, and no pollution. The sea area where the fish is built is also required to have a smooth flow, with a large tidal range, in order to facilitate sub-seedlings and irrigation and irrigation. In addition, there are abundant sources of eel seedlings, and transport facilities are also factors that should be taken into consideration when selecting sites.
2. Fish?e built
Before the construction of the fish?e, detailed surveys must be carried out to design and construct the terrain. General fish?e projects mainly include embankments, gates, and trenches.
(1) Embankment: Generally, the top width is more than 2 meters. If the traffic arteries should be widened to more than 5 meters, the embankment height should exceed 1 meter above the maximum tide and flood in the past years. A 1:2 to 1:3 slope is generally used.
(2) Construction of the gate: After the e-mail address is determined, the gate must be built first. The gate serves to control the water level, drain water, regulate water quality, raise seedlings, and harvest. The construction of the gate is good or bad, it has a great impact on the sodium seedlings, and it is also the key to the output of the fishery e. The common gate is a cement structure, and a gate of width 1.2 to 1.5 meters is generally set in an area of ​​5 to 7 hectares. The architectural form is divided into single hole, double hole or porous gate. Three sluice gates are installed on the sluice gate, a gate is installed in the middle, and a flat net is installed in one slot to block the entry of enemy creatures and prevent the escape of fish, or to install a cone-shaped net when entering the water. A trough is also installed in a trough outside to prevent weeds from entering or installing cones at harvest. The distance between the three gates should be farther. When some of the gates are flooded, the difference in flow rate between the different water layers on the gates will be reflected, and the water flow will be slow, which is beneficial to the emergence of the seedlings and harvesting.
(3) Set up water pools and ditches: Water pools are important sites for fish inhabitation. They are made by artificial excavation. Fish are concentrated in pools at the time of harvest to facilitate fishing. There are several waters in the pool that communicate with each other, known as the central ditch. Generally, the mouth is 6 to 8 meters wide, the bottom is 3 to 4 meters wide, and the depth is 1.5 to 2 meters. In addition, it is also necessary to excavate the lateral grooves separated by the ring ditch and the central ditch, and the branch ditch separated by the lateral ditch, etc. The ring ditch is often formed by taking soil when constructing the ditch. Ditches are also places for fish habitat activities.
3. Fish breeding technology
(1) Preparations before cultivation: After the fish have been farmed or after one year of cultivation, they must do well in the drying, cleaning, digging and removing pests.
The fish?e is generally harvested in the fall. After the harvest, the gates are all opened and the water is discharged. The gates are then closed and exposed to sunlight for several days to kill the algae, aquatic grasses and other harmful organisms, and accelerate the decomposition of organic matter in the soil. It is beneficial to the reproduction of plankton at the time of restocking in the coming year.
After one year's breeding of fish, the original ditch is often congested with sludge, and in the winter, the sludge in the ditch is excavated to make the water flow clear. After the embankment hits the waves, the typhoon hits, and crabs punch holes, leakage occurs, especially near the gates. Therefore, it is necessary to strengthen maintenance in the winter.
In shallow water or nearshore, many wild grasses, such as mangroves and weeds, are often grown and removed. In addition, large-scale carnivorous fish within the e should be removed with drugs prior to the production of fish. Commonly used drugs are tea cakes, fish rattan and so on. The amount of tea cake used is 25-30 grams per cubic meter of water. After drying, the cake is powdered. When used, it is slightly soaked and sprinkled in the e. The amount of rattan extract is 1 to 2 grams per cubic meter of water. It is first diluted with fresh water and sprinkled in the e.
(2) Na Miao and Feeding Fish: In the eel sister breeding, the source of the seedlings is mainly obtained from the seedlings. Since the carp is the most excellent species for fish farming, the carp seedlings are the main targets of the seedlings. On the coast of Guangdong, carp seedlings appeared from December to April, with the largest number in February. Nan Miao has two methods. One of them is reverse water seedlings, that is, when the tide begins, the water level in the sea area is lower than the water level in the e, and the gate is opened slightly to allow the water to flow out slowly. As the tide rises, the gate gradually opens and the speed of the control flow is less than the speed of fry swimming. Take advantage of the anti-water habits of carp seedlings to concentrate a large number of fish seedlings near the gates. When the water level in the e is higher than about 10 cm from the sea, open the floodgates so that the fish fry back into the e. When the water level inside and out of the gate approaches equilibrium, the floodgates close immediately. This fara smaller carp seedling works well. Another method is to use water-based seedlings. When the tide starts to rise, the water level in the e is higher than the sea area. Open the gate and drain the water in the e to attract the fish to swim against the gate. When the water level in the e is slightly higher than the sea area, close the gate and wait until the water level in the sea area is higher than 10-15 cm in the water level in the e. Place the fishing net in the inside of the gate (in the end of the net towards the inside of e). At this time, open the gate quickly. , Using the current of water, bring the fry that is concentrated near the gate into the e. This method is suitable for the inclusion of large individuals, not easy to reverse the water of the fish fry, in the second half of this method.
The number of fish, natto, and seedlings often does not meet the needs of aquaculture. Some salmon fry that have been caught or artificially propagated from natural sea areas must be put in order to increase the production of fish e.
(3) Routine management: The daily management of fish and eculture includes drainage irrigation and overbank maintenance.
The purpose of drainage and irrigation is to control the water level and regulate water quality. During the cultivation period, it is necessary to control the fish through drainage and irrigation as required. The water level of the e is at a certain level, and when the water quality is deteriorated, it should be improved through drainage and irrigation. Drainage and irrigation are generally arranged during the high tide period because the quality of the seawater is better.
Overbank gate maintenance is the main content of daily management. It is mainly to check if there are any damages and loopholes near the fish gates, and to find out the problems and do maintenance work in time. Especially during the typhoon and flood seasons, inspections must be strengthened to ensure production safety.
Although the fish e culture mainly depends on the fish itself, the body of the fish provides the bait for the cultured fish. If necessary and suitable conditions can be applied artificially for the application of fertilizers to promote the propagation of the food organisms in the fish e, providing a richer diet. Fertilizers commonly used for fish?e are inorganic fertilizers or organic fertilizers.
(4) Harvesting: Fish?e Fish harvesting is small and large. A small income is a combination of the usual drainage. The method is based on the fish growth situation and the actual needs of the fish, in the drainage time at the gate installation of nets for fishing operations. Working hours are generally scheduled for dusk or in the morning. Drainage speeds are preferably 2 to 4 meters per second at the end of the net. The big income is arranged twice a year) during the lunar calendar months of May and November, but it is generally scheduled for the end of the year because the lowest water level during the first year of the low tide is suitable for the complete cleaning of fish. At the time of harvest, they are usually first used for tidal opening and nets to open gates for drainage and fishing. Then, tea cakes are spread from the end of the tea cake and gradually pushed toward the sluice gate to allow the fish to swim to the gate, and then catch it with a trawl. The big income can also be arranged before the typhoon arrives.
The water suitable for farming salmon is very wide, and various sea and freshwater bodies can be cultured. The common seawater or brackishwater culture methods include fish breeding and coastal pond farming.