Fish is one of the staple foods. Fish are susceptible to invasive diseases, some of which are dangerous for the health of the fish themselves and can cause their mass death, others are dangerous for humans, animals and birds that feed on fish. Invasive diseases drastically reduce the quality of fish products: sick fish are emaciated, their tissues have a reduced content of nutrients - fats, proteins and carbohydrates, vitamins and microelements. Invasive diseases occur against the background of pronounced clinical symptoms, which worsens the presentation of fish products. Affected fish, due to low commercial and nutritional qualities, is used as food for people and animals with restrictions or is subjected to special neutralization. At the same time, there is a decrease in the grade and quality of products, culling of individual batches, a ban on the sale of fresh fish.