From Latin resistentia - resistance, opposition.

Resistance of the organism - the ability of the organism to withstand prolonged exposure to low concentrations of a toxic substance or high concentrations but for a short period of time. Resistance of the organism is closely related to the lifestyle of fish.

Natural resistance of fish is an innate ability of the organism to resist the aggressive influence of pathogenic factors of biotic and abiotic nature, including pathogens of infectious and invasive diseases and products of their vital activity (exo- and endotoxins).