Bigeye larvae are the foundation for crab breeding, and their quality directly affects the survival rate of young crabs from stage II to V. When purchasing bigeye larvae, it's essential to pay attention to several key factors to ensure success in crab farming.
Before buying bigeye larvae, farmers should familiarize themselves with the entire breeding process, including the source of broodstock, feeding practices, and breeding cycles. It's recommended that the broodstock used for producing seedlings comes from natural lake environments, with male and female crabs sourced from different waters to ensure genetic diversity. The size of the broodstock is also important: females should weigh at least 125 grams, and males at least 150 grams.
Using Artemia as a feed can result in healthier crabs compared to substitutes like freshwater quail or egg yolk. The incubation period for bigeye larvae typically lasts 19–21 days, with an ideal emergence temperature around 21°C.
To assess the quality of bigeye larvae, consider the following:
- **Color**: High-quality larvae should appear light yellow, shiny, and transparent under a microscope, without signs of microorganisms or filamentous bacteria.
- **Body condition**: Healthy larvae are robust, uniform in size, show strong phototaxis, feed actively, and have good swimming ability. When gently squeezed and released, they should spread out quickly.
- **Size specifications**: Normal bigeye larvae should range between 120,000 and 140,000 per kilogram, with no more than 170,000 per kg. This ensures fewer fake seedlings and smoother development into juvenile crabs.
- **Water conditions**: When the larvae emerge, the water salinity should not exceed 4‰, and desalination should last at least 7 days. The water temperature during emergence should be around 21°C, with a maximum temperature difference of 2°C (up to 4°C) between the nursery and culture ponds.
**Precautions to take:**
1. Before the larvae leave the pond, it’s advisable to disinfect them to reduce disease risk and eliminate weaker individuals.
2. Stop feeding before harvesting, use light traps for collection, drain the water, and evenly distribute the larvae in containers.
3. Transport early-stage seedlings during the day and late-stage ones at night. Protect them from sun and wind, and ensure proper ventilation during transit. Spray water every two hours to maintain humidity.
4. Allow a gradual acclimation process before introducing the larvae to the pond: first open the container, spray water on the larvae for 5 minutes, then submerge the box and larvae in pond water for a short time. Let them sit on the shore for 15 minutes, repeat the process, and finally release them slowly into the pond.
By following these guidelines, farmers can significantly improve the quality and survival rate of their crab seedlings.
Aluminium Safety Railing,Balcony Railing,Aluminum Protective Railing,Villa Railing
Xuzhou Guifeng Metal Technology Co., Ltd , https://www.guifengmetal.com