ScientificFarmingWeb

This disease is addressed with many names such as fish poisoning, erythematic migrants, sealer’s finger, whale finger, bubble finger, fish hand, fish handler’s disease etc. it affects the people who handle the fish and their wastes. The incubation period for the bacteria is 1-7 days and the symptoms are fever, pain in muscles and joints, sometimes internal infection may occur in the nervous system and heart, bluish-purple spots etc. Commonly it is observed on the hands. Any cut or small opening on the skin surface can cause the bacteria from fish to enter the body, but the bacteria have an inability to proliferate in the warm body conditions and remains confined to the affected area causing itching, pain and swelling. Antibiotics can help relieve the problem.

Excess nitrate levels in water bodies where fish are farmed cause brown blood disease. It can be also be addressed as nitrate poisoning because the nitrate in water oxidizes the hemoglobin in the fish blood cells and converts it into a compound called met hemoglobin. This compound obstructs the oxygen intake due to which the fish in water experience oxygen stress and die immediately. Administering proper antibiotics can help overcome this problem, but most importantly care should be taken such that the disease doesn’t occur.

Fungus can develop within the tanks or fish farms due to several reasons such as poor water quality, low maintenance of the farms, improper hygiene, un-noticed diseased or injured fish in the pool, dead fish which start decomposing etc. cleaning the fish farming tanks or areas and disinfecting them properly is a necessity to control fungus within the tanks or pools.

This is a method by which exchange of water is minimized due to use of bio-filtration and other environmental control techniques to recycle the used water. The water is treated with a series of processes such that the need for fresh, clean water is reduced to maintain fish or other aquatic stock in the farms. Some of the measures in the recirculating of water involve bio-filtration, solid removal, oxygenation, pH control, temperature control and bio-security.

Each species of fish has a different feeding habit and behavior; also, it is dependent upon the stage of the fish. At the larvae stage rice barn and groundnut oil cake in the ratio 1:1 is given for 15 days so as to produce fry fish of 300 g weight and 15-25 cm length. Similarly, at the fingerling stage and fully grown stage, the ratio of feed is increased. The feeding methods can be studied in detail at Fish Farming Business.

Fish are raised in a hatchery and then released into water bodies so as to supplement the present population or to create a new population of fish. Generally stocking is done for commercial benefits, but sometimes it is also useful in restoring the threatened species of fish. The minimum stocking density is for all different species of fish are different and it also depends on the size of the fish. For e.g., if the size of silver carp is 7-10 cm, then the stocking density is 3000 fish per hectare. Similarly, for Mrigal fish of the same size the stocking density is 500 fish per hectare.

This structure has double walls. The outer wall is made of muslin cloth and the inner wall is made of round meshed mosquito net material. The dimension of the outer wall is 1.5 x 1 x 1 m and the inner wall minimum dimensions are 1 x 0.75 x 0.75 m. The eggs from the breeding area are shifted to hatching hapa and are uniformly spread here. The minimum time for hatching is 18 – 24 hours. When the hatchlings get out of the inner area, the mesh is carefully removed to dispose the egg shells.

It is enclosed like a box made of meshed mosquito net material and erected through bamboo poles fixed in the pond or pool. Generally, the hapa are covered with plain cloth over the top, but breeding hapa has an open top for inserting and removing brood fish. The minimum dimensions of a breeding hapa are 2 x 1.5 x 1 m. The breeding hapa is filled such that there are two male fish for one female fish. Once the eggs get hardened and embryo twitches, the brood fish are removed from that place without harming the eggs.

Hapa is a cage made of fine mesh material and is set up in a fish farm using bamboo poles to raise fish of small size. These are created in shallow water bodies, where the flow of water is low. This type of cage formation makes it easy for harvesting and is durable.