How to determine if fish are suffering from pollution poisoning

Fish deaths can be caused by many factors such as disease, oxygen deficiency, toxic algae, mechanical injury, and pollution poisoning, and pollution poisoning is the most common type of fatal cause. Below are several methods for visually judging common types of pollution poisoning, for reference in production.

Heavy metal pollution poisoning. Heavy metals refer to metals with relatively high density, such as lead, manganese, zinc, etc. The gills of poisoned fish appear grayish-white and secrete large amounts of mucus, forming flocculent deposits that block the gills and cause respiratory impairment; poisoned fish often float and swim at the water surface.

Fish with lead poisoning show a noticeably black body color. Fish with copper poisoning show a grayish-white body color, with gill filaments appearing light green. Fish with chromium poisoning show a dark yellow body surface, with gill filaments appearing yellowish-brown.

Sodium pentachlorophenate pollution poisoning. Sodium pentachlorophenate is one of the most common organochlorine compounds, mainly used as a molluscicide, and it is also an insecticide. Fish poisoned by sodium pentachlorophenate swim frantically, jumping and darting about aimlessly, and before death, poisoned fish tend to burrow into grass and stay close to the shore. In general, wild miscellaneous fish die first, followed by bighead carp, silver carp, grass carp, common carp, crucian carp and other fish dying in succession, and after death the body color turns black. Fish with chronic poisoning have blackened fin rays and protruding eyeballs.

Methamidophos pollution poisoning. Methamidophos is an organophosphorus pesticide, commonly used as an insecticide. Poisoned fish are irritable and restless; after frantic swimming and colliding, they move slowly, show sideways swimming, with the head down and tail up and other symptoms, and finally sink to the bottom and die.

Dimethoate pollution poisoning. After dimethoate poisoning, symptoms are not obvious, but the liver of the fish is noticeably enlarged.

Carbofuran pollution poisoning. The main symptom of fish poisoning is body curvature, with excrement at the anus forming a "trailing tail".

Pyrethroid pesticide pollution poisoning. Pyrethroid pesticides are highly effective, low-toxicity, low-residue pesticides, but for fish they still belong to the highly toxic category, and they act rapidly with strong killing power. After poisoning, fish show restlessness, with the operculum open, and the struggling time from turning belly-up to death can last as long as 12 hours. After death, the eyeballs protrude, with bleeding spots on the fundus, fluid accumulation in the abdominal cavity, and the gills appear grayish-white.

Herbicide pollution poisoning. Herbicides have contact action and are low-toxicity to fish, but at high concentrations they can still cause acute poisoning and death in fish. Because herbicides have a killing effect on algae, polluted pond water is prone to oxygen deficiency, fish deaths can occur at any time of day, water transparency increases greatly, and phytoplankton in the water basically disappear.