Due to application of modern technology the productions of fishes have been increased but at the same time the percentage of diseases in fishes also increases. So attention is not only given to the production of fishes but also to the diseases of the fishes. The diseases may occur either due to physical as well as chemical changes of the water or by various kinds of organisms. Generally the fish mortality is caused by various kinds of organisms. Hence the various groups of organisms like bacteria, fungus, protozoa, worms and Crustacea are attacking the carps and causes various types of carp diseases.
Some important carp disease and its preventive measures are described below.
BACTERIAL CARP DISEASE
The diseases like 'Tail and fin rot', dropsy, eye disease etc., are caused by bacteria.
Tail and fin rot carp disease
This is caused by bacteria known as Pseudomonas. In the primary stage, the disease starts in the terminal part of the tail fin of the carps. Gradually the disease spreads in the tail fin as well as in other fins and the muscles of the body are also involved in decomposition. Eventually the fins are decomposed and detached from the body. Hence the diseased carps cannot move and unable to take any food. As a result, they become weak and gradually they die.
i) The fishes affected by this carp disease are to be removed from the stocking pond and are kept in the water of copper sulphate solution (5 mgm. of copper sulphate per litre of water) for about 5 minutes.
ii) There is some beneficial effect if 200-250 gm. of potassium permanganate solution of water is applied in pond during night for successive seven days.
iii) Lime is to be applied in the pond during this period.
This type of carp disease is caused by the bacteria known as Aerornonas. Due to the attack of these bacteria there is gathering of plenty amount of fluid in the abdomen of the carps, as a result the abdomen swells up. The fluid comes out through the vent simply by gentle pressure on the abdomen. There is looseness of scales of the fishes.
i) Infected fishes are kept for about 5 minutes in 1% or 2% dilute Potassium permanganate solution.
ii) There will be a good result after application of Potassium permanganate into the pond water.
FUNGAL CARP DISEASE
This type of carp disease is caused by a fungus known as Branchiomycessanguinis. This fungus attacks the fishes mainly in the summer season. The mycelium of the fungus penetrates into the gills of the fishes and draws its food; as a result the gills become pale and whitish. In the end there is respiratory trouble due to the rotting of the gills and then fishes die. In addition to Gill-rot disease, 'Fungal abscess' also may occur in carps.
As the preventive measure of Gill-rot disease the affected fishes are to be immersed in 3-5% saline water for 5-10 minutes and then released to the pond.
CRUSTACEAN CARP DISEASE
Argulosis is a carp disease which is caused by a minute crustacean animal known as Argulus. This is commonly known as carp lice. This Argulusremains attach to the external surface of the fish by hooks and suckers. So this ectoparasite draws blood from the host. As a result the carp become weak and even death may occur.
i) As a preventive measure of this type of carp disease bamboo sticks are to be firmly implanted in the different places in the pond ; so that the affected fishes can have the opportunity for mechanical friction of the body against the bamboo stick ; as a result the ectoparasite, Argulusis detached from the body of the carps by mechanical friction.
ii) Potassium permanganate and lime are to be distributed in the pond, as a result the ectoparasites will be detached from the body of the carps.
PROTOZOAN CARP DISEASE
The carp disease myxosporidiosis is caused-by a protozoa known as Myxobolus. Due to the attack of Myxobolus, the white spots are developed on fins, gills etc. The scales are also detached from the body.
i) The affected fishes are to be kept in the saline water.
ii) Lime is to be added in the pond water.
HELMINTH CARP DISEASE
The fishes are also affected by flatworms known as Gyrodactylus. This worm attacks the skin and gills of the fishes. There is a heavy secretion of mucus from the body of the carps and then death of carp may happen.
Affected fishes are kept in the saline water (30 gm salt in one liter of water) for 5 minutes and as a result, the worms will die and the gills of the carps are gradually becoming normal.