Detailed Explanation of Key Technical Points for Restocking Fish Fingerlings After Heavy Rain

Every year, some areas are hit by typhoons and heavy rain, causing fish pond embankments to collapse and serious fish escapes. After the rainy season, timely restocking of fish fingerlings will reduce the losses caused by flooding to a minimum. The techniques for restocking fish fingerlings after heavy rain are introduced below.

1. Sources of fish fingerlings

After heavy rain, if the weather is hot, fish fingerlings are not convenient to transport over long distances, so they are generally obtained locally, or caught from nearby natural water bodies. The caught fish fingerlings should be stocked nearby, and the time out of water must not be too long. All operations should be carried out in net cages or in a seine net, but the time should preferably not exceed 2 hours, and operations out of water are strictly prohibited.

2. Preparation before stocking

(1) Repair the embankments breached by floods, block off water bodies connected to the outside, and reinforce dangerous sections of embankments with new soil and tamp them solid to prevent seepage. If problems are found, solve them immediately; ensure that the embankment will not breach again.

(2) Observe the situation of fish escaping from the pond to ascertain the details and determine the species and quantity to restock.

(3) Use quicklime, alum and other substances to clarify the turbid water after the disaster and purify the water quality. If the water body is too lean, apply a small amount of fertilizer to enrich the water quality.

3. Stocking

The fish fingerlings to be stocked should be healthy fish with intact scales and fins, strong jumping ability and lively swimming. Fish that are thin and weak, slow to react, have congested body surfaces or mechanical injuries should all be culled. The species to be stocked can be determined according to the situation. The stocking size should preferably be large, and the stocking density can be appropriately sparse so that they can all grow to marketable size by the end of the year. Before the fish fingerlings are put into the pond, they should be soaked in 2%-3% salt water or 1-22 mg/L crystalline trichlorfon for 3-5 minutes to prevent the spread of pathogens.

4. Management

After the fish fingerlings are stocked, the feeding of concentrated feed should be strengthened to ensure rapid growth of the fish fingerlings. A daily feeding amount of about 8% of the total weight of the pond fish is relatively appropriate; specifically, a slight remainder observed after feeding should be the standard. If a large number of silver carp and bighead carp are stocked, fertilizer should also be added. Fertilization should follow the principle of small amounts applied multiple times. Organic fertilizer must be fully fermented before being applied to the water body, at 50-100 kg per mu; chemical fertilizer can be ammonium bicarbonate or urea dissolved in water and evenly splashed to cultivate natural food organisms in the water, at 5-8 kg or 3-5 kg per mu respectively.