A Comprehensive Analysis of Key Points for Drug Use in Fish Farming
In recent years, China's aquaculture industry has developed rapidly, and the degree of intensification in aquaculture has also been increasing quickly. At the same time, the aquaculture environment has been continuously deteriorating, causing a decline in the immunity and disease resistance of cultured species, while the incidence of disease has increased significantly. Moreover, due to factors such as mutations in pathogenic bacteria, new diseases and difficult-to-treat diseases have frequently emerged. At present, these diseases are mainly treated with medication. This article discusses the development, classification, factors affecting drug action, and problems existing in the use of fishery drugs in China.
I. The Development and Classification of Fishery Drugs
Fishery drugs refer to all substances used to prevent, control and treat diseases, insects and pests of aquatic animals and plants, promote the healthy growth of cultured species, enhance the body's disease resistance, and improve the quality of aquaculture water.
1. The Development Process of Fishery Drugs in China
Fishery drugs have run through the development process of China's aquaculture industry, and with the improvement of scientific and technological levels and the continuous deepening of research, the composition, classification and functions of fishery drugs have also been continuously improved. Generally speaking, this can be divided into three stages.
①The First Stage
Folk, simple and proven prescriptions formed through exploration and accumulation in production practice, using industrial products and processed products of some agricultural and sideline products in practical application. For example, croton in pond-clearing drugs, and quicklime commonly used in disinfection and sterilization, etc. Although fishery drugs at this stage have the advantages of readily available raw materials, low prices, simple use and wide application, at the same time these fishery drugs have not undergone scientific pharmacological and toxicological tests, and in the process of use they also have the disadvantages of unstable efficacy and poor safety.
②The Second Stage
Drugs with good efficacy are screened out from human medicines, livestock and poultry medicines, plant protection medicines and other aspects of medication through a series of pharmacological and toxicological tests and transplanted into the aquaculture industry. These are also the mainstream fishery drugs in China at the present stage. Such fishery drugs have stable efficacy and high safety in enhancing the immunity of aquaculture species, improving their stress response to adverse environments, and preventing and treating diseases, but at the same time they have a great impact on the environment. Moreover, with the enhancement of drug resistance of pathogenic bacteria, many drugs at this stage are no longer suitable for practical application and have even been banned.
③The Third Stage
Mainly new drugs with unique efficacy and solutions for major diseases that are currently seriously harmful to the aquaculture industry and adverse aquaculture environments. Such drugs have not only improved in efficacy, but also pay more attention to being green, environmentally friendly and free from secondary poisoning. This is also the future development direction of fishery drugs in China.
2. Classification and Functions of Fishery Drugs in China at the Present Stage
There are many types of fishery drugs in China with different names on the market. According to their different functions, they are mainly divided into the following categories.
①Antibacterial Drugs
Drugs that inhibit the growth of pathogenic bacteria, which can be divided into antibiotics, sulfonamides, furans and other chemotherapeutic agents.
②Disinfectants
Agents used for disinfection are called disinfectants. They can be divided into halogen types, oxidizing agents and dye types, etc.
③Anthelmintics and Insecticides
Drugs that expel internal parasites and kill external parasites, such as trichlorfon, copper sulfate, ferrous sulfate, albendazole, etc.
④Anti-mold and Antioxidant Agents
Mainly used as feed additives to prevent feed from becoming moldy and oxidizing. Such as mold-removing agent, sodium propionate, etc.
⑤Nutrients and Metabolism Improvers
Mainly to prevent diseases caused by metabolic disorders and to treat nutritional deficiency diseases. Such as hormones, vitamins, etc.
⑥Anesthetics
Agents used when collecting eggs from brood fish, transporting live fish, and tagging and performing surgery on fish. Such as ether, MS222, etc.
⑦Environment Improvers
Drugs that improve the water environment in which aquatic animals live. For example, substrate improvers include quicklime, etc.
II. Factors Affecting Drug Action
The occurrence of fish diseases is the result of mutual influence and interaction among the fish body, environmental factors and pathogens. Similarly, when treating fish diseases, the action of fishery drugs is not only affected by their own properties, but also by environmental factors, pathogens and the fish body.
1. Factors Affecting Drug Action
①Physicochemical Properties of Drugs
The physicochemical properties of drugs are closely related to the strength of drug action. Among them, the physical properties that affect the effectiveness of drug use include the volatility, water solubility, lipid solubility and adsorption capacity of drugs; the chemical properties that affect the action of drugs include the pH, stability, degree of dissociation of drugs, and displacement reactions between drugs and metals, etc.
②Drug Dosage, Dosage Form and Route of Administration
When treating fish diseases, each drug has a minimum effective concentration, and only when the drug exceeds this concentration will it take effect. However, this does not mean that efficacy can be improved and treatment time shortened by infinitely increasing the dosage of the drug, because each drug also has a lethal concentration. For the same fish disease, different dosage forms of fishery drugs have different effects due to differences in their bioavailability. Different routes of administration lead to different absorption speeds, and therefore different concentrations in the body. Therefore, when using fishery drugs, it is essential to select appropriate fishery drugs and routes of administration according to the type of fish disease, and to use them within the effective concentration.
③Interactions Between Drugs