What are the problems faced in composite fish culture and methods to solve these problems?
Answers
Hazards in Composite Fish Culture
Composite fish farming runs the risk of encountering several incidental hazards, which may cause heavy losses unless they are anticipated and remedial measures taken in time in order to overcome them.
Most of the problems emanate because of poor management.
Hazards may be either biological or problems of management or harvesting.
Biological Problems:
Biological hazards arise from the existence of weeds, predatory fishes, insects and snakes in the culture ponds.
These problems can be controlled if sufficient measures are taken before stocking fishes in between successive cultures.
Aquatic weeds, if any found in the pond can be very effectively controlled by the introduction of weed eating fishes like grass carp and Puntius species.
The common predatory fishes Mystus, Ompok, Wallago, Notopterus, Oreochromis, Gobius, etc. and weedy fishes are Salmostoma, Esomus, Barbus, Ambasis, Rasbora, Amblypharyngodo, etc. are found in the ponds and compete with fingerlings of carps.
These should be eradicated during the preparation of the pond.
Aquatic insects such as beetles: Cybister, Stemolopus; bugs: Belostoma, Anisops and dragon fly nymphs, etc. should be eradicated.
Others like snakes also cause considerable damage to the fish crops by feeding on fingerlings.
Molluscs in large numbers always affect the fish adversely. They can be controlled by stocking the fish, Pangasius pangasius in the pond. They feed on molluscs and reduce their infestation.
Due to the early maturity and natural breeding of the common carp, the rate of these fishes is increased and the stocking density of the culture pond is greatly altered unless some precautionary measures are taken.
Hence, common carp may be harvested before they are fully ripe. Otherwise aquatic weeds can be kept in the corners of the pond to lay eggs which are adhesive in nature.
The weeds with attached eggs can be removed and the eggs, if so desired, can be incubated separately to obtain hatchlings. By this, the farmers will avoid the breeding of common carp in the pond with less cost and at the same time raise the spwan for sale.
Common carp, because of its burrowing nature, it can spoil the dyke by making holes in it.
Crabs also damage the dyke. Tilapia is a continuous breeder; hence it must be avoided in the ponds.
Algal blooms with Microcystis, Euglena, etc. which are found generally in summer months cause serious problems of dissolved oxygen.
During day time, oxygen is supersaturated and in the night oxygen is depleted.
The chemical method is good for eradication of blooms. Pumping of freshwater into the pond at the time of emergency is a safe method.