Experience Sharing on Raft-Style Abalone Farming in Shallow Seas

I. Selection of Sea Area Selection of sea area for abalone farming: clear and flowing water, fresh water quality, no pollution, no rivers nearby, abundant seaweed resources, relatively stable seawater salinity at medium salinity. Specific requirements are: 1. Water depth: for abalone farming sea areas, seawater should not be too shallow; ideally the water depth can reach between 15-20 m. ⟦4 <p>I. Selection of Sea Area</p><p>Selection of sea area for abalone farming: clear and flowing water, fresh water quality, no pollution, no rivers nearby, abundant seaweed resources, relatively stable seawater salinity at medium salinity. Specific requirements are:</p><p></p><p>1. Water depth: for abalone farming sea areas, seawater should not be too shallow; ideally the water depth can reach between 15&mdash;20 m.</p><p>2. Water temperature: the survival water temperature range for abalone is 1-28°C, and the optimum growth water temperature is 14-22°C. Therefore, in abalone farming sea areas, the winter water temperature should not be lower than 1°C, and in the high-temperature season the water temperature should not exceed 28°C.</p><p>3. Salinity: abalone is a marine organism of medium salinity, and the seawater salinity is required to be stable at 29&permil;-31&permil; as suitable, with a minimum not lower than 27&permil; and a maximum not exceeding 36&permil;.</p><p>4. Water flow: because abalone likes unobstructed water flow, sea areas with regular reciprocating currents should be selected, and the flow velocity should preferably be 50-60 m/min.</p><p>5. Physicochemical factors of water quality: in sea areas where abalone likes to inhabit, the pH value is 8.0-8.4, dissolved oxygen is not lower than 4 mg/L, ammoniacal nitrogen is not greater than 100 mg/L, and organic oxygen consumption is below 0.5&mdash;1 mg/L.</p><p>II. Material Preparation for Abalone Farming</p><p>1. Wooden stakes: the wind and wave resistance of raft-style farming depends on the wooden stakes, so the wooden stakes for abalone farming must be large and sturdy, with a required diameter of 20&mdash;25 cm and a length of not less than 80&mdash;100 cm.</p><p>2. Frame ropes and root ropes: both frame ropes and root ropes use 25&mdash;30 mm polyethylene rope; frame ropes are 60&mdash;70 m long, and root ropes are 30&mdash;40 m long, or can be determined according to water depth conditions.</p><p>3. Hanging ropes: use &phi;10&mdash;15 mm polyethylene rope, generally 8&mdash;10 m long, with 1 rope per hanging line.</p><p>4. Sinker stones: the sinker stones needed for abalone farming are either stone blocks or made of cement, each 2&mdash;2.5 kg.</p><p>5. Buoyancy: use &phi;30 cm plastic floats, 25 per rack, or increase buoyancy according to the growth condition of the abalone.</p><p>6. Rubber stick: made of rubber, &phi;8 cm, 40 cm long; during management the rubber stick is mainly used to remove miscellaneous algae and some small shellfish on the net cages.</p><p>7. Small iron shovel: make a small iron shovel 20 cm long and 5 cm wide. It is mainly used to remove oysters, barnacles and some other shellfish attached to abalone shells.</p><p>III. Selection of Abalone Farming Equipment:</p><p>Whether the equipment for growing abalone is reasonable directly affects the abalone grow-out results. Based on many years of production practice and screening, at present three kinds of abalone cages have the best results. The main grow-out forms are:</p><p>1. New-style abalone cage:</p><p>The plastic tray produced in Rongcheng has a specification of 52 cm&times;52 cm, a four-layer combined square tray cage with rounded corners, with a steel bolt fixed in the middle, 64.5 cm long and &phi;12 mm; the cage wall is sewn from 2&mdash;2.5 cm polyethylene mesh. This equipment has good water permeability, light regulation, sturdiness, economy and practicality, and is currently a relatively ideal abalone farming equipment.</p><p>2. Modified cage: modify the original scallop farming cage into 8 layers, with 40 cm plastic trays in the middle, the trays covered with 0.8&mdash;1 cm round holes, and the cage wall sewn from 1.5&mdash;2 cm polyethylene mesh. The disadvantage of this equipment is that feeding bait is inconvenient.</p><p>3. Introduced Japanese-style zipper multi-layer cage: &phi;60 cm, 5 layers in total, each layer 40 cm high, the cage wall sewn from 2&mdash;2.5 cm polyethylene mesh, and the feeding opening combined with a zipper. The disadvantages of this abalone cage are high cost and the zipper is easily damaged.</p><p>IV. Transportation of Seedlings</p><p>There are two transportation methods for abalone seedlings: dry transport and water transport. For short-distance transportation with a time not exceeding 15 hours, dry transport can be used. For long-distance transportation, water transport should be used. When transporting seedlings, the abalone should be transported together with the polyethylene corrugated boards to avoid the abalone seedlings squeezing each other, being injured and dying. The abalone seedlings can also be detached and transported together with kelp in polyethylene net bags.</p><p>1. Dry transport: the transport container can be a plastic foam box or wooden barrel, which must be fully soaked and washed with clean seawater before use. Place a layer of soaked large-leaf grass or fresh small kelp at the bottom of the container, then place the abalone seedlings, together with the attachment boards, or already detached and put into small net bags, on the large-leaf grass, one layer of abalone seedlings and one layer of large-leaf grass or fresh small kelp, not exceeding three layers. With this transportation method, the abalone seedlings are evenly distributed, not squeezed, not injured, and humidity can be maintained; the transportation survival rate reaches 98%, and it is currently the best transportation method.</p><p>2. Water transport: for long-distance transportation, first detach the abalone seedlings and put them into polyethylene net bags. A net bag with a specification of 40&times;30 cm can hold about 1000&mdash;1500 abalone seedlings. During transportation, put the net bags into canvas barrels on the ship; each cubic meter can hold 3000-5000 abalone seedlings. During the journey, use a water pump to draw water and replace fresh seawater once per hour. Under flowing water conditions, the survival rate of abalone seedlings in water transport for more than 100 hours can reach 96%. When transporting seedlings, be sure to choose clear fine weather, the air temperature should be above 5°C, and direct sunlight must be prevented. After the seedlings arrive at the destination, they must immediately be put into cages and released into the sea for rearing; never put them into cages overnight.</p><p>V. Management of Grow-out at Sea:</p><p>1. Grow-out density: the new-style abalone cage has a specification of &phi;52&times;52 cm, a four-layer combined square tray cage with rounded corners; each layer can hold about 150 abalone with shell length above 3 cm; one cage with four layers can hold 600. The &phi;40 cm 8-layer modified cage can hold 80 abalone seedlings with shell length above 3 cm per layer; one 8-layer modified cage can hold 640. The Japanese-style zipper multi-layer cage has a specification of &phi;60 cm and can hold 200 abalone seedlings with shell length above 3 cm per layer; one cage with five layers can hold 1000 abalone seedlings.</p><p>2. Bait feeding: the main bait varieties for abalone are kelp, wakame, and sea lettuce, followed by sargassum, Sargassum thunbergii, etc. The feeding amount is determined according to the feeding condition of the abalone, generally 15&mdash;20% of the abalone body weight. Feeding frequency: once every 8 days from March to April, once every 5 days from April to June, once every 7 days from June to July, once every 10 days from July to September, once every 7 days from September to December, and once every 15 days from December to March. When feeding, first remove residual bait and wash off floating mud and attachments inside the abalone cage, creating a good environment for abalone growth.</p><p>3. Timely thinning: by mid-April of the following year, when the abalone grows to 4.5&mdash;5 cm, promptly carry out cage separation, measurement and thinning. For the new-style abalone cage, 150 per layer is thinned to 80 per layer; for the modified cage, 80 per layer is thinned to 50 per layer; for the Japanese-style zipper multi-layer cage, 200 per layer is suitably thinned to 120 per layer.</p><p>4. Farming water layer: the abalone farming water layer is generally 4&mdash;5 m, which can avoid the attachment layer of oysters, mussels, etc. Entering winter, as the water temperature gradually decreases, adjust the water layer to 7&mdash;8 m, with a cage spacing of about 3 m.</p><p>5. Removal of predators and pests: in daily management, promptly remove shellfish, miscellaneous algae and floating mud on or inside the cage walls, especially oysters, mussels, barnacles, sea squirts, bryozoans, sea anemones, etc. attached to abalone shells. Most of these harmful organisms can attach to net cages and abalone shells, causing reduced water permeability of the abalone cage, affecting the movement and growth of the abalone, making it difficult for the abalone to feed, and causing it to become thin and weak and die. At present, for these harmful organisms, prevention and manual removal are mainly adopted. Prevention means avoiding their peak attachment period on the basis of understanding their reproduction patterns, and medicinal coatings can also be used for prevention and removal. Manual removal uses a rubber stick to lightly strike miscellaneous algae and shellfish on the abalone cage; the rubber stick does not damage the net cage. For what cannot be knocked off, shellfish attached to abalone shells are removed cleanly with a small iron shovel. In addition, after each big sea swell, promptly wash the floating mud inside the cage to prevent death caused by blockage from floating mud.</p><p>6. Safe production: frequently inspect the cage frames, wooden stakes, root ropes, hanging ropes, floats, and hanging sinker stones. If rope tangling is found, solve it promptly. Especially before typhoons arrive, carefully inspect whether various abalone farming facilities are firm. Entering winter, as the water temperature gradually decreases, try not to leave the water and expose them to the air; when the air temperature is below 5°C, do not expose them above the water surface.</p>

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