First, the selection of pro-ginseng (sea cucumber) is crucial for successful breeding. The best choice is to select sea cucumbers from a pool with high synchrony and plump bodies. The skin should be intact and clean, with each individual weighing between 250 to 350 grams. The gonads should account for more than 15% of body weight, and the body wall should make up over 50%. For every 1000 cubic meters of seedlings, approximately 400 to 500 individuals are needed. Each female can produce about 3 to 5 million eggs.
When collecting the pro-ginseng, they are typically placed in long tanks, either elliptical or shoe sole-shaped, depending on whether the majority are females or males. Choosing an elliptical or shoe sole shape better suits nursery requirements.
For transportation, wet transport is preferred, ideally done around 4 a.m. when temperatures are low, traffic is light, and conditions are stable. Use plastic tanks of 50 to 70 liters each, filled with seawater from their original culture tank. Insert a frozen mineral water bottle to maintain temperature. Each tank holds 25 to 35 individuals. Within 10 to 12 hours, the ginseng remains clean and active.
Second, the cultivation of parent stock and spawning. Upon returning to the nursery, the ginseng should be kept in natural seawater with the same salinity as their original pool. After they expel waste, change the water at 5 p.m. to stimulate spawning. The process of collection and transport is a strong stimulus, and most will spawn naturally. If not, keep them for 3 to 5 days, changing water daily without excessive stimulation. On day 5, introduce flowing water and river-like conditions to encourage spawning. Place the ginseng in an empty pond for 40 minutes, then use a hose to stimulate them for 20 minutes. Spawning usually occurs within 2 to 4 hours, peaking between 9 a.m. and noon, so monitoring is essential.
After spawning, water must be filtered through sedimentation and sand filters, then passed through a 1000-mesh bag. Turbidity should be 50–100 mg/L. Add 3 g/m³ of EDTA sodium to chelate heavy metals. Maintain salinity at 27–32 and water temperature at 17–20°C. Add 2 g/m³ of antibiotics like oxytetracycline or streptomycin.
Before spawning, males are separated and placed in another pool. Spawning ponds have a depth of about 0.7 meters. After spawning, parents are moved to a new pool. Eggs are transferred to a 1.4-meter deep pool, with micro-aeration and manual burping every hour to ensure even distribution and prevent oxygen depletion.
The next morning, count the fertilized eggs. Density should be small—around 8–10 per mL. If too dense, split the pool using a siphon tube, stirring the water to distribute eggs evenly.
Third, cultivating planktonic larvae. Spawning should occur before the fertilized eggs develop into small ear-like larvae. When larvae become mobile, collect them from the upper layers using a 300-mesh sieve and transfer them to nursery ponds at 0.5–1/mL.
Daily management includes water changes: first two days use gradual filling, then replace 60–70% of the water daily with a 250-mesh cage. Maintain natural temperature and salinity, and add 3 g/m³ of EDTA after each change.
Feeding is critical. Sea cucumber larvae cannot digest algae with cell walls. Use mixtures of Dunaliella salina, Chaetoceros, Phaeodactylum tricornutum, and marine red yeast. Dry yeast tablets can also be used effectively.
Algae quality is important: clear, bright color, no protozoa or aging cells. Monitor regularly. Algae density should be 1 million/mL for Dunaliella, 2×10²/mL for other species.
Feed larvae according to developmental stages. Small ear larvae get 3000 cells/mL, with equal parts Dunaliella and Chaetoceros. As they grow, adjust ratios accordingly. Feed every 8 hours after water changes, and stop feeding when larvae reach the juvenile stage.
Monitor under a microscope. If larvae have full stomachs with visible food, feeding is adequate. Adjust amounts based on observations.
Over 11–13 days, larvae develop into juveniles. Regular microscopic checks are necessary. Track growth: small ears (450–600 µm), medium (600–800 µm), large (800–1000 µm). Normal increase is 50 µm/day. Observe water cavity development, which changes from round to long, then to irregular shapes.
Eventually, larvae develop into juvenile ginseng. Most transition from one larval stage to the next within 1–2 days.
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