Increasing the population of rotifers directly in ponds is an effective strategy to address feeding challenges, reduce production costs, and enhance the survival rate and quality of fry. The following are the key steps involved in this technique:
1. Drain and Clean the Pond: Rotifers can emerge from resting eggs that lie dormant in pond sediments. It has been found that there are over 10 million rotifer resting eggs per cubic meter of sediment in fishery ponds. These eggs act as a natural "seed" for the next generation of rotifers. Draining the pond helps stimulate these eggs by increasing their exposure to warmth, while cleaning the pond removes predators that may threaten the rotifers. Additionally, introducing fresh water acts as a positive trigger for egg hatching. When the average water temperature is between 20-25°C, draining the pond with approximately 100 kg of quicklime per 667 m² (about one mu) can lead to a significant increase in rotifer numbers within 8-10 days.
2. Apply Organic Fertilizer: Studies have shown that adding about 26 kg of cow dung or human waste per 667 m² of pond provides sufficient nutrients for rotifers. To further boost the number of resting eggs in the water, pond mud can be mixed with a 1% solution of quicklime, which enhances the availability of nutrients and promotes better hatching conditions.
3. Control Predators: Once rotifers appear in the pond, leeches often follow, as they feed on similar microorganisms such as bacteria, algae, and plankton. Leeches are more efficient filter feeders than rotifers, and if left unchecked, they can outcompete them for food, leading to a decline in rotifer populations. To manage this, applying trichlorfon at a concentration of 0.5 mg/L across the entire pond can effectively eliminate leeches while preserving the rotifers. Combining this method with organic fertilization can extend the peak rotifer period from the natural 3-5 days to 15-20 days, providing a longer window for fry feeding.
4. Refresh the Water: When conditions are favorable, rotifers reproduce rapidly. However, after reaching their peak in just 1-2 days, they may face environmental stressors such as low oxygen levels. If not addressed, they will enter a dormant state and stop reproducing. By adding fresh water, the density of rotifers can be reduced, helping to maintain the peak population for a longer period and ensuring a more stable food supply for fry.
This approach not only boosts the natural productivity of the pond but also supports sustainable aquaculture practices, making it a valuable technique for small-scale and commercial fish farmers alike.Henan chinamian foods CO.LTD , https://www.ooossooo.com