Key Points and Methods for Comprehensive Prevention and Control of Fish Surfacing

From June to October each year, temperatures are high and the weather is muggy. If fish are stocked at excessive density and water quality deteriorates, it can easily cause fish to surface due to oxygen deficiency, or even suffocate to death. In severe cases, all pond fish can die within 1 to 2 hours. Therefore, correctly analyzing the causes of fish surfacing and identifying the signs and severity of fish surfacing is of great significance for strengthening routine management and promptly rescuing fish from pond turnover.

(1) Causes of fish surfacing.

There are mainly the following aspects: (1) Blindly overfeeding and overfertilizing, resulting in excessively fertile water, massive proliferation of plankton, rising oxygen consumption by organic matter and declining dissolved oxygen. (2) Poor natural conditions and excessive stocking density, leading to insufficient dissolved oxygen in the water. (3) Excessive pond bottom silt and deteriorated water quality. (4) No new water added for a long time, resulting in fertile but aging water quality. (5) The water body is polluted and contains certain toxic and harmful substances. (6) Long periods of clear weather without rain and excessively high water temperature easily lead to water quality deterioration. (7) When water quality is relatively fertile and light is poor on cloudy and rainy days, phytoplankton photosynthesis is weak, and oxygen replenished from the atmosphere is limited.

(2) Premonitory signs of fish surfacing.

Fish surfacing mostly occurs in the muggy weather of summer and autumn and during sudden changes between clear and rainy weather, especially at night or dawn. Muggy weather, strong light exposure, sudden thunderstorms, and high temperatures; continuous rainy and muggy weather with no wind or heavy fog, low air pressure, and weak light; long periods of clear weather without rain, and heavy feeding and fertilizing; water quality being too dense, sudden changes in water color, and reduced transparency; fish without disease suddenly reducing their food intake, and massive death and decomposition of plankton; fish gathering in the upper layer of the water body and swimming in scattered groups, with patches of splashing visible; sudden deterioration of water quality, and small fish and shrimp gathering and swimming along the shore, etc., are premonitory signs that pond fish are about to surface and cause pond turnover.

(3) Identification of fish surfacing.

According to the severity of fish surfacing, the degree of oxygen deficiency in the water can be judged. The specific distinctions are as follows: (1) If fish surfacing is seen in the pond in the early morning, and the fish immediately sink after clapping hands or throwing a small stone into the pond, or automatically sink shortly after the sun comes out, it indicates that the oxygen deficiency is not very serious and belongs to mild surfacing. (2) If there is no response to frightening or they still do not sink after 9 o'clock, it indicates serious oxygen deficiency and belongs to mild surfacing. (3) If at midnight fish spread from the center of the pond to the shore and do not sink when frightened, it indicates severe surfacing. (4) If from midnight to the first half of the night black carp, grass carp, etc. gather along the shore, all surfacing, breathing rapidly, and floating weakly, it indicates that the fish are about to cause pond turnover very soon.

(4) Prevention of fish surfacing.

(1) Do a good job in water quality management. Achieve the "three maintains," namely maintaining water transparency at about 25 cm; maintaining sufficient dissolved oxygen in the pond water; and maintaining the pond water "fertile, tender, refreshing, and lively." Pay attention to frequently adding new water, preferably maintaining a slight water flow state, and promptly remove leftover bait and feed in the pond. (2) Improve the ecological environment of the fish pond, change shallow ponds into deep ponds, change dead-water ponds into flowing-water ponds, and change small ponds into large ponds. Before @#@233@#, thoroughly clear the pond and disinfect it. (3) Equip with aerators. Generally, one aerator is installed for 0.2 to 0.3 hectares of water surface. The general operating times for aerators are: turn on at noon on clear days, turn on in the morning on cloudy days, turn on in the middle of the night during continuous cloudy and rainy days, and do not turn on in the evening; turn on immediately when fish surface; during the peak growth season of fish, insist on turning it on every day. It is required that the operating time be longer in the evening or at midnight and shorter at noon. (4) Carry out drug prevention. When water quality ages and plankton reproduce excessively, promptly use quicklime, trichlorfon, copper sulfate and other drugs to regulate water quality and kill excessive plankton. When the water quality is acidic, quicklime can also be used for regulation. (5) Use seine nets and people entering the pond to stir the pond mud, promote the decomposition of organic matter, and regularly break the stratification phenomenon of the water. Generally once every 10 days or so, stir the pond at noon on clear days for 1 hour, and every 20 to 30 days apply 15 to 20 kg of quicklime per 0.067 hectares after mixing with water and splash it over the whole pond to improve water quality. (6) Reduce the storage quantity of fish in the pond. For fish ponds where severe surfacing often occurs, promptly catch part of the fish for market. Also remove various wild and miscellaneous fish.

(5) Rescue of pond turnover.

Once signs of fish surfacing are discovered, treat them immediately. For mild surfacing, immediately add new water to the pond and reduce the feeding amount. For fish ponds where severe surfacing has already occurred, promptly turn on the aerator and inject new water. If there is no aerator, use a wooden stick to strike the water surface to increase oxygen, or drive a wooden stake into the fish pond, tie on a hollow bamboo tube about as thick as a bowl's mouth and about 1.5 m long for irrigation to increase dissolved oxygen in the bottom layer; or apply ammonium sulfate and calcium peroxide, etc. to increase oxygen, so as to oxidize organic matter and remove toxic substances. At the same time, splash into the water some slurry that can precipitate organic matter and absorb toxic substances. Generally, the amounts used per 0.067 hectares with a water depth of 1 m are as follows: gypsum powder 3 to 4 kg, alum 3 to 5 kg dissolved in water, salt 10 kg dissolved in water, yellow mud and salt water (10 kg each of yellow mud and salt mixed evenly), yellow mud plus urine with 10 kg of yellow mud and 10 kg of human urine, yellow mud slurry 5 to 7.5 kg, and limewater 7 to 15 kg dissolved in water can all alleviate fish surfacing.