Control of Vibrio bacteria in shrimp seed production

Vibrio is the source of serious damage to farmed shrimp. To limit Vibrio diseases in commercial shrimp, first of all, there must be healthy and disease-free breeding stock. Therefore, it is necessary to manage Vibrio infection in the hatchery.

Preparing for seed production

Clean and disinfect the entire factory, nursery tanks, tools and equipment with 100 ppm chlorine or 200 ppm formalin for 2 days and then dry in the sun to kill fungus.

The broodstock shrimps that are raised to maturity and allowed to spawn have good quality, intact and balanced bodies, shells that are not rough or cracked. Antennae are 1.5 - 2 times longer than the body length, with complete appendages. Natural color, normal activity. Negative for TSV, WSSV, YHV, IHHNV, MBV. Intact reproductive organs. Males have swollen, milky white sperm sacs. Females have eggs from stage 1 to stage 3.

Water with salinity 26 - 35‰, let settle for 1 - 2 days, supply to the tank for filtration. Before use, water must be disinfected with ozone or chlorine (25 - 30 ppm) for 24 hours. Neutralize residual chlorine with thiosulphate in a 1:1 ratio. Use a chlorine test to check residual chlorine, water supplied to the breeding tank has a residual chlorine content < 0.1%

At the end of each production batch, the factory system, tanks, equipment and tools directly serving production must be cleaned and disinfected periodically or after each use to ensure veterinary hygiene for aquatic animals.

Parent shrimp care

The broodstock shrimp tank has a depth of 0.5 - 0.7 m, salinity > 28‰, temperature: 28 - 290C, pH 7.5 - 8.5; DO > 5mg/l, aeration 24/24.

Density: 8 - 10 fish/m2.

Food: 50% red bloodworm + 50% fresh squid, can add 10% oyster, Vitamin, intestinal probiotics. Disinfect squid with ozone generator for 8 - 10 minutes; disinfect red bloodworm, oyster with PVP-Iodine 5ppm for 1 minute before feeding. Feed about 10 - 20% of body weight, 4 times/day. Monitor food consumption daily to adjust food intake accordingly. In the late afternoon, use a net to scoop out shrimp shells and remains, leftover food. Periodically bathe mother shrimp every 3 days with KMnO4, Iodine at a concentration of 5 ppm for 30 minutes.

Water change: 100 - 200%/day or 20%/day if there is a biological filter.

Prepare the nursery tank

The tank is disinfected with 100 ppm chlorine for at least 24 hours. Then use water to wash away the residual chlorine on the tank surface, supply disinfected seawater through a cotton filter bag, then add 10 ppm EDTA and aerate for 24 hours before releasing the Nauplius larvae into the nursery.

Environmental conditions of the nursery tank: Water depth 0.8 - 1.0 m. Salinity 28 - 32‰. Temperature 26 - 300C, pH from 8.0 - 8.6, aeration 24/24.

Larval rearing tanks can be round, square, cement or composite tanks, with a volume of 4 - 10 m3.

Larvae management and care

After 30 - 32 hours of spawning, collect Nauplius in the spawning tank and transfer to a 20 - 100 liter basin (plastic barrel), gently aerate to evenly distribute the larvae, bathe the larvae with KMnO4, 5 ppm or Iodin 5 ppm for 3 - 5 minutes. Transfer the larvae to the rearing tanks with treated water. If there is a temperature difference of > 10C and 2‰ in salinity, Nauplius must be acclimatized. The acclimatization time must meet the requirements: 10C/30 minutes or 1 - 2 ‰/30 minutes.

Stocking density: 100 - 200 Naupli/liter

Nauplius stage, need light, even aeration, larvae nourish yolk so no need to provide food. Observe regularly, when Zoae larvae appear, start adding more food.

In the Zoae stage, the larvae filter feed continuously, so it is necessary to provide dry algae and fresh algae 4-5 times/day. The amount of algae is gradually increased from the end of Zoae 1 to Zoae 2, increasing to the maximum at the Zoae 3 stage. From the Zoae 2 and Zoae 3 stages, synthetic food (Lansy, Frippak...) can be added 2-3 times/day. Depending on the water color and health of the larvae, increase or decrease the amount of food accordingly.

In the Mysis stage, the amount of algae needs to be gradually reduced. Larvae at this stage have an active predatory behavior, and their food is zooplankton. Therefore, at this stage, Artemia larvae are mainly used in combination with synthetic foods such as Lansy, Frippak, etc. used alternately. At this stage, increase aeration to avoid the phenomenon of Mysis larvae sinking to the bottom, periodically siphon the bottom and change the water every 5-7 days to ensure clean water quality.

After Mysis stage 3, the larvae move to the Postlarvae stage. The time for Mysis larvae to move to the Postlarvae stage depends on the water temperature, usually from 4 to 6 days. Each day of raising Postlarvae is counted as 1 year of postlarvae. Postlarvae care techniques are similar to the Mysis stage. Postlarvae have the habit of clinging to the walls and bottom of the tank, and can swim against the current, and they have the habit of eating each other when hungry. Postlarvae shrimp's food is Artemia larvae and synthetic food. During this stage, the bottom must be siphoned regularly and the water changed every 3 to 4 days.

To control Vibrio bacteria in seed production, prevent disease and improve resistance for shrimp entering the post-larval stage, periodically add probiotic Zp25, mix into shrimp feed, 3 times/day, with a dosage of 15% of shrimp feed.

Treat water in the larval rearing tank with Iodine or KMnO4, dosage 2 ppm.

When Postlavae are 13 - 15 days old, they can be harvested, transferred to the nursery pond to become shrimp larvae or released directly into the shrimp pond.

According to Thuysanvietnam