1. According to the famous scientist Pleczar, any non-cellular microscopic infectious entity composed of proteins and nucleic acids and capable of multiplying only in living host cells is called a virus.
2. According to scientist Bawden (1947), viruses are obligate parasites invisible to the naked eye.
3. According to scientist (A. Lwoff (1952), Virus is a virus.
4. According to scientist George (1983), viruses are microscopic harmful substances composed of nucleoprotein core and protein coat, which cause disease in plants and animals. Dr. Siddiq Publications

Virus means Virum or poison. The word Virus is taken from Virum. Microscopic non-cellular organisms composed of nucleic acids and proteins that multiply and cause disease inside living cells, but behave like inert substances outside living cells are called viruses. In ancient times, any poisonous substance that causes disease was called a virus.

1. Protein needs: Fish fulfills the lion’s share of our protein needs. Roo fish plays an important role in this.
2. Conservation of Species: This fish needs to be cultivated for the conservation of roe species.
3. Employment: Many people have got employment by farming rue fish.
4. Earning foreign exchange: By meeting the demand of roe fish in the country, the surplus can be sold abroad and foreign exchange can be earned. Dr. Siddiq Publications
5. Reservoir use: unusable reservoirs can be used for cotton fish farming by processing.
6. Fish and rice Bengali: Fish and rice Bengali to retain this past tradition, fish farming is necessary.

1. Creation of fish sanctuaries: For the preservation of rue fish, various rivers, canals, canals and haor-baors or their special parts need to be declared as fish sanctuaries. Dr. Siddiq Publications
2. Pollution Prevention: Care should be taken to prevent various types of garbage, chemical fertilizers, fungicides and pesticides from contaminating the water.
3. Reducing salinity: Rui is a freshwater fish. Therefore, the salinity of water should be reduced as far as possible.
4. Stop harvesting of mother fish: The hunting of mother fish must be stopped. Fishing should be prohibited during the breeding season of roe fish. Dr. Siddiq Publications
5. Encouraging fishermen: Fishermen should be encouraged about the importance of fish farming and fish. Dr. Siddiq Publications
6. Stop river encroachment: River encroachment should be stopped completely. Fish breeding areas should always be kept safe. Dr. Siddiq Publications
7. Formation of river commission: River commission should be formed. Necessary steps should be taken to restore and protect the river. Dr. Siddiq Publications
8. Prevention of change in river course: If the course of the river changes, the habitat and breeding ground of the fish will change. Therefore, the change in the course of the river must be prevented.
9. Egg stock: Public, private and private stocks of cotton fish eggs should be kept.
10. The water body should be controlled by the fisherman without any person ruling the water body.
11. Conservation of Halda River: Halda River is the only cotton breeding ground in Bangladesh. Halda river is known as fish mine rich in natural resources. This natural breeding area should be preserved.
12. Stop poisoning: Fishing with poison should be banned.
13. Public awareness: Public awareness should be created in various ways.
14. Adoption of scientific methods: Fish and fish eggs should be caught and preserved scientifically. Dr. Siddiq Publications

10 restrictions have been imposed of Halda Fisheries Heritage
1. No one can catch fish in Halda river.
2. Only eggs can be collected during the breeding season under the supervision of the Department of Fisheries. Dr. Siddiq Publications
3. No one can disturb the biodiversity of Halda river.
4. Halda river cannot be polluted.
5. No one can throw garbage in this river.
6. No one can change the natural course of Halda river.
7. No dam can be built in this river.
8. No project to collect water from Halda river can be taken up.
9. During fish spawning, motorized boats cannot play in the river.
10. Halda river can only be used for research purposes.

Halda River is the largest natural fish breeding center in Asia. This river originates from Badnatali hill in Ramgarh police station of Khagrachari district. The river crosses Raujan in Phatikchari and Kalurghat in Hathajari and merges into the Karnaphuli river. The river has a length of 95 km and a depth of 25–50 feet.
Eggs of carp like Rui, Katla, Mrgel, Kaliboush etc. are collected directly from Halda river. The main season for fish egg collection in Halda river is Baishakh-Jaisthya month. The mother fish lays her eggs during heavy rains and thundering clouds on Amavasya and Purnima tithis. In the last fifties, 70% of the country’s total fish demand was met by Halda river fish. In 1946, 4000 kg of eggs were collected from Halda river. In 2007, 350 kg of eggs were collected. Hence Halda river is called as natural gene bank and fish mine. This river is called mother fish maternity clinic. Dr. Siddiq Publications
At present 4 bends of Halda river have been cut. Switchgates have been constructed in an unplanned manner. Industrial factories have grown uncontrollably. Fish breeding grounds have been destroyed. The mother fish is being killed.
In 1987, the Barighona section of Hathazari in Chittagong was officially declared a sanctuary for the first time. In 2013, 70 recommendations were made regarding the conservation and development of the natural fish breeding grounds of the Halda River. A modern laboratory called Halda River Research Laboratory has been established in Chittagong University. In 2021, 23,422 acres of Halda River has been declared as Halda Fisheries Heritage. Along with the declaration of Halda Fisheries Heritage, 10 restrictions have been imposed.
1. No one can catch fish in Halda river.
2. Only eggs can be collected during the breeding season under the supervision of the Department of Fisheries. Dr. Siddiq Publications
3. No one can disturb the biodiversity of Halda river.
4. Halda river cannot be polluted.
5. No one can throw garbage in this river.
6. No one can change the natural course of Halda river.
7. No dam can be built in this river.
8. No project to collect water from Halda river can be taken up.
9. During fish spawning, motorized boats cannot ply in the river.
10. Halda river can only be used for research purposes.

(i) Halda river in Chittagong (world’s largest natural breeding ground).
(ii) Yamuna River Aricha, Sirajganj, Phulchhari Ghat, Bahadurabad
(iii) Garai river in Kushtia
(iv) Rajshahi and Chapainawabganj on Padma river
(v) Brahmaputra of Mymensingh
(vi) Madhumati River
(vii) Ariyal Kha River
(viii) Challan Bill, Hakaluki and Tangua Haor.

Sufficient oxygen, suitable temperature, adequate food, current and turbid water and enemy-free environment are required for good reproduction of roe fish. Cotton fish do not lay eggs without suitable environment. In the absence of a suitable environment, mature eggs are absorbed by the body. This phenomenon is called atresia. Atresia occurs year after year in closed ponds. Therefore, roe fish does not breed in closed reservoirs. Only physical aging occurs. Closed ponds contain more organic waste. Such water has high BOD (Biological Oxygen Demand) value and low O2 content. Regeneration does not occur in stagnant water. When O2 is low, sexually mature fish cannot stimulate the gonads to induce sexual reproduction. Eggs and larvae do not easily fall prey to enemies in the clear water of closed reservoirs. Excretion is uncertain as the water in closed reservoirs fluctuates. So roe are not interested in spawning in stocked ponds.

(i) Fresh water bodies with streams
(ii) Phenyl or foamy turbid water
(iii) Presence of adequate amount of oxygen in water
(iv) Heavy rain with thunder
(v) Upstream hill slopes
(vi) Water temperature 24-28 degree centigrade
(vii) River bends
(viii) Fluctuation of water
(ix) Monsoon and Amavasyaba Purnima Tithi.

1. Oxygen and nutrients are renewed in the flowing water. Embryos and larvae get enough oxygen from water. Dr. Siddiq Publications
2. The continuous flow of water protects the eggs and larvae from predators.
3. The rapid circulation of the flowing water ensures the excretion of fish.
4. Sediment carried by running water makes the water cloudy. Turbid water protects fish eggs and larvae from predators.
5. Flowing water transports fish eggs and larvae. In the new environment, there is enough food for chickpeas and chickpeas. Dr. Siddiq Publications