There's an art to winter pond fish harvesting, and mastering the method is key

Winter is a favorable time for harvesting and marketing pond fish, but winter harvesting is also a potential trigger for fish diseases the following year. Therefore, extra care must be taken during winter harvesting to avoid injuring the fish as much as possible, so as to reduce the occurrence of fish diseases and improve the economic returns of the pond.

1. Clear debris from the pond before harvesting. Wooden stakes set up in the pond for theft prevention, uncleared large rocks, and aquatic plants on the water surface such as water hyacinth and alligator weed can all interfere with normal seining. To carry out winter harvesting smoothly and safely, obstacles in the pond must be cleared before harvesting to make seining easier. Significant unevenness or deep pits on the pond bottom can also reduce harvesting efficiency and should be leveled during the dry-pond stage before stocking fish.

2. Drain water before harvesting and refill after harvesting. Adapt to local conditions and do a good job of draining and filling the pond. The water in an overwintering pond is relatively deep; if part of the water is not drained before harvesting, seining becomes inconvenient, and the fish can easily escape during harvesting. Therefore, before harvesting, the water depth must be lowered to 1-1.5 m. After harvesting, immediately refill to raise the depth above 2.5 m to increase water temperature, so that market-sized fish that have not reached the standard can overwinter safely and be kept for the next year's rearing, allowing continued profit.

3. Choose the right net. First, choose the net size: the length of the net should be at least 1.4 times the width of the pond, and the height of the net should be at least 2 times the water depth. Second, the mesh size should be determined according to the size of the fish to be caught. If the mesh is too small, undersized fish will also be dragged up, causing unnecessary injury. Generally, seines are made of nylon netting.

4. Choose good locations for setting and hauling the net. For setting the net: first, set the net in shallow water and haul it in deep water; second, when it is windy, set the net at the downwind end of the pond and haul against the wind. During seining, the bottom rope forms an angle with the pond bottom; by the time the net is hauled in, the fish are densely concentrated. To prevent fish from slipping out under the bottom rope, the hauling-in location should be chosen where the pond embankment slope forms a 30°-40° angle with the water surface, and the slope there should be flat and free of debris.

5. Set the net gently and haul it in quickly. When harvesting, be sure to set the net gently and haul it in quickly. Remember to organize the net properly before setting it, place it on one side of the pond, then gently put the bottom net, net body and float line into the water along the pond edge, and pull from both sides at the same time. When hauling, move slowly over the front 1/3-1/2 of the pond surface to avoid making the fish swim wildly, jump and collide too early; when hauling to the rear half of the pond surface, quickly close and lift the net to reduce net-collision injuries and escapes. The people pulling on both sides should apply force in a coordinated way, not suddenly with explosive effort, and should keep the dragging speed basically uniform, not fast at times and slow at others.

6. The upper and lower ropes must be coordinated. During seining, the upper rope is light and the lower rope is heavy; the upper rope must move along with the lower rope, and the upper rope should be slightly ahead of the lower rope. If the upper rope is too far back, fish can easily escape; if it is too far forward, it can lift the lower rope off the pond bottom and cause the net to "flip," letting large numbers of fish escape. As the haul approaches its end, the upper rope should be gradually tightened and raised to prevent fish from jumping out.

7. Avoid continuous operations day after day. Because winter water temperatures are low, fish metabolism is slow and resistance is poor. If fish that do not need to be harvested are repeatedly injured within a short period, the wounds are difficult to heal, which will allow saprolegnia fungi to invade and cause disease the next year, reducing production. Therefore, do not work continuously day after day just for immediate gain.

8. Precautions. Harvesting by seining should preferably be done in clear weather; if the pond water quality is poor, seining is best done in the early morning or forenoon. Stop feeding for one day before seining to avoid injuring the fish; seining must not be done when the pond is short of oxygen. After harvesting, select the brood fish and the small fish that have not reached market size, soak them in 3%-4% salt water for 10 minutes to disinfect and prevent disease, and then put them back into the pond for reproduction and growth the next year.