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What are the symptoms of fish poisoning?

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1. Symptoms of mass poisoning in fish In winter dry seasons, fish poisoning by pyrethroid pesticides is likely to occur in aquaculture water surfaces, ponds, reservoirs, ditches and other water bodies. After poisoning, fish in groups mainly float on the water surface, drift with the waves, and lose balance. At the beginning of poisoning, they show momentary excitement, then swim slowly, respond sluggishly to surrounding stimuli, lie still and on their sides, slowly wag their tails, slowly open and close their mouths, and finally sink to the bottom and die. From the onset of poisoning to death, the toxic effect takes a short time, and the mortality rate of fish after poisoning is high. Fish show slightly different symptoms of poisoning by different pyrethroid pesticides. At present, the main varieties commonly used in agricultural production on the market include fenpropathrin (Meisaoli), fenvalerate (Sumicidin), and cypermethrin. They are described separately as follows: ① Fenpropathrin 20% emulsifiable concentrate formulation. The technical material is a brown liquid, insoluble in water, soluble in organic solvents, stable under neutral and acidic conditions, and easily decomposed and inactivated by alkali. This pesticide is a pyrethroid insecticide with the general characteristics of pyrethroid insecticides: broad-spectrum, high-efficiency, fast-acting, low residual toxicity, and long-lasting. This pesticide kills insects by contact action, stomach action, and antifeeding action. After mass poisoning, fish stop swimming, rise to the surface, dart about, and then stop at the bottom. In low-concentration water, fish show neurological poisoning symptoms that last for 1 day to 2 days; at high concentrations, fish die rapidly. Fenpropathrin has moderate toxicity to humans and livestock, and high toxicity to fish. ② Fenvalerate is a yellow oily liquid, soluble in xylene. Some fish poisoned by fenvalerate have congested gills and are prone to deformities. ③ Cypermethrin is yellow or brown, soluble in various organic solvents, and has contact, stomach, and antifeeding effects. It belongs to neurotoxic insecticides. When fish are poisoned in groups, they first show excitement, swimming wildly and erratically, then lose balance, twitch, become paralyzed, and are near death.

1. Symptoms of mass poisoning in fish In winter dry seasons, fish poisoning by pyrethroid pesticides is likely to occur in aquaculture water surfaces, ponds, reservoirs, ditches and other water bodies. After poisoning, fish in groups mainly float on the water surface, drift with the waves, and lose balance. At the beginning of poisoning, they show momentary excitement, then swim slowly, respond sluggishly to surrounding stimuli, lie still and on their sides, slowly wag their tails, slowly open and close their mouths, and finally sink to the bottom and die. From the onset of poisoning to death, the toxic effect takes a short time, and the mortality rate of fish after poisoning is high. Fish show slightly different symptoms of poisoning by different pyrethroid pesticides. At present, the main varieties commonly used in agricultural production on the market include fenpropathrin (Meisaoli), fenvalerate (Sumicidin), and cypermethrin. They are described separately as follows: ① Fenpropathrin 20% emulsifiable concentrate formulation. The technical material is a brown liquid, insoluble in water, soluble in organic solvents, stable under neutral and acidic conditions, and easily decomposed and inactivated by alkali. This pesticide is a pyrethroid insecticide with the general characteristics of pyrethroid insecticides: broad-spectrum, high-efficiency, fast-acting, low residual toxicity, and long-lasting. This pesticide kills insects by contact action, stomach action, and antifeeding action. After mass poisoning, fish stop swimming, rise to the surface, dart about, and then stop at the bottom. In low-concentration water, fish show neurological poisoning symptoms that last for 1 day to 2 days; at high concentrations, fish die rapidly. Fenpropathrin has moderate toxicity to humans and livestock, and high toxicity to fish. ② Fenvalerate is a yellow oily liquid, soluble in xylene. Some fish poisoned by fenvalerate have congested gills and are prone to deformities. ③ Cypermethrin is yellow or brown, soluble in various organic solvents, and has contact, stomach, and antifeeding effects. It belongs to neurotoxic insecticides. When fish are poisoned in groups, they first show excitement, swimming wildly and erratically, then lose balance, twitch, become paralyzed, and are near death.

2. Main symptoms of individual fish poisoning The body color of the fish turns black from the back to the tail. In poisoned fish, the degree of blackening of body color varies with different doses: at high concentrations, the body color change is obvious; at low concentrations, the body color change is slight. It also varies with the duration of exposure to the toxin: when the concentration is the same, a long poisoning time causes a large body color change, while a short exposure time causes a small body color change. After being stimulated, poisoned individuals become abnormally excited; some leap out of the water, swim rapidly without purpose, then dive into the water again, repeating this alternately many times. The eyes show exophthalmos, and there is congestion or hemorrhage in the fundus. The operculum bleeds, the gills are pale white with black debris, the operculum and mouth are open, and from turning white to death, the struggling time can last up to 12 hours. Examination of the internal organs shows no obvious enlargement of the gallbladder, pale bile, punctate congestion in the liver, degeneration and brittleness, and the liver color becomes pale, like earth-yellow.

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