Two-year-old ruhi fish become fertile. Females reach sexual maturity at 51-70 cm and males at 60-65 cm.

Ruhi is a freshwater carp. Its life cycle is completed in several stages. Its steps are:
1. Sexual Maturity: Two-year-old ruhi fish become fertile. Females reach sexual maturity at 51-70 cm and males at 60-65 cm.
2. Breeding Season: In nature, ruhi fish breed once a year. Rainy season or June-July is the best time for their breeding. During this time the water is flowing and cloudy. Turbid water is suitable for the survival of fish. Siddique Publications
3. Spawning: Fecundity is the ability of fish to produce eggs. The process of laying fish eggs is called spawning. Roe fish lives in stagnant water but lays its eggs in flowing water. It is called protamodromous. The suitable environment for egg laying is water temperature 24-280 C. And water contains a lot of oxygen. Cotton fish lays eggs on Amavasya or Purnima. At this time, the male fish secretes steroid hormones into the water and attracts the female fish for reproduction. The female fish lays about 19,00,000 eggs in the turbid water under the obsessive effect of retaxis. Eggs that float in water are called pelagic eggs and eggs that sink are called demersal. Dr. Siddiq Publications
4. Fertilization: The male fish releases sperm on the eggs. The water in the river changes and mixes with the sperm and egg. Fertilization occurs when the sperm and egg meet. As a result of fertilization, the zygote is created. Dr. Siddiq Publications
5. Development : The process by which the zygote divides repeatedly into a full-fledged organism is called fertilization. This is done in three steps.
(i) Embryonic cleavage: Cleavage begins 30-45 minutes after formation of the zygote. The zygote divides by cleavage to form micromere and macromere cells. In the process of blastulation, these cells become blastomeres. Blastomere cells are arranged in a certain layer. During gastrulation, blastomere cells are arranged in three layers. Ectoderm, Mesoderm and Endoderm.
(ii) Hatching of larval stage: Larva emerges from egg within 15-18 hours. The larva is called an egg. Dimpona age of 72 hours is called renupona. In this condition, the embryo takes on a light yellow color. Notochord and nerve cord are formed. Eyes, hearing and chromatophores are formed. Air sacs and digital fins are present.
(iii) Post larval hatching: In this stage the yolk sac is destroyed. Operculum, dorsal fin, caudal fin etc. arise. Air sacs are divided into two parts. The tail is homocircular. The nostrils are fully divided, the eyes are equal and the fleshy mouth is formed.
6. Anguli Pona: If the length of Pona is 7-12 mm then it is called Dhani Pona. When the chick is 9-30 days old, it is called Anguli chick. Fingers, fins, barbel etc. are formed in fingerlings.
7. Brood fish: Morphological and structural changes occur in the fingers. Transforms into a full-fledged fish. attains sexual maturity. When it reaches sexual maturity, it is called brood fish.

1. Respiration: Crackers contain oxygen. Fish carry out respiration with the help of this oxygen.
2. Sound Production: Crackers help in sound production. Vibration occurs when air is trapped in the diaphragm wall of the crack.
3. Echo generation: Crackers generate sound waves. These sound waves reach the cochlea through the Becherian tube.
4. Buoyancy: The air trapped in the crackers helps the fish to float in the water.
5. Relative weight control: Crackers control relative weight by increasing or decreasing the amount of gas inside the body.
6. Hearing: Crackers help the fish to hear.
7. Protecting the center of gravity: The gas on one side of the air bag is transferred to the other side and protects the center of gravity of the body in water. Siddique Publications
8. Adaptation: At any depth of water, the size of the alveoli changes to suit the environment. As a result, fish swim actively at any depth and adapt. Siddique Publications

Each air sac consists of 2 chambers. Atrium and Posterior chamber.
1. Atrium or small chamber: The small chamber of the air sac is called the atrium. It is covered by a thin wall consisting of two layers. The outer layer is called tunica externa and the inner layer is called tunica interna. The tunica externa is composed of connective tissue and the tunica interna is composed of smooth muscle. There is a gas gland of red color in its inner wall. This gas gland is called reti mirabili. The air sacs are filled with gases released from the reti mirabili. Most of the gases in the air are oxygen. However, there is a small amount of carbon dioxide and nitrogen. Siddique Publications
2. Posterior chamber or large chamber: The large chamber of the air sac is called the posterior chamber. It is covered by a thin wall consisting of two layers. The outer layer is called tunica externa and the inner layer is called tunica interna. The tunica externa is composed of connective tissue and the tunica interna is composed of smooth muscle. There is a gas gland of red color in its inner wall. This gas gland is called reti mirabili. Reti Mirabili absorbs gas.
The air sacs of roe fish contain tiny bones. These bones are called Becherian bones.

The long sac filled with air in the coelom cavity between alimentary canal and kidney of fish is called patka or swimming sac or air sac. This is two types. namely-
1. Physocleistus: Absence of ductus pneumaticus between esophagus and air sac is called physocleistus. For example, kai fish, taki fish etc.
2. Physostomes: Ductus pneumaticus between esophagus and air sac is called physostomes. For example – cotton fish, cuttle fish etc.

When the blood flows through the blood vessels against the flow of water, it is called countercurrent system. Backflow occurs because the concentration of oxygen is higher than that of blood in retrograde flow. Oxygen present in water dissolves easily in blood due to a chronic low concentration. As a result, maximum oxygen (80%) is received by the blood. The lamellae present in the gills increase the oxygen absorption surface. As the tips of the gill rakers cross each other, water flow slows down and gas exchange takes longer.

Respiration in ruhi fish is done in two stages. Inhalation or inhalation and exhalation or exhalation.
1. Respiration or Respiration: Ruhi fish takes in oxygen dissolved in water to carry out respiration. For unidirectional water flow, water enters through the stomata and exits through the gills. In this case the mouth and pharynx act as pumps. First, the mouth and pharynx expand and the stoma opens. Water enters the mouth and pharynx. The front of the gill chamber then expands and water enters the gill chamber. Then the pressure in the gill chamber decreases and water flows up the gills. Finally, the buccal and pharyngeal chambers are narrowed. At this time, the oral cavity is closed so that water cannot escape. Dr. Siddiq Publications
2. Inhalation or Exhalation: Contraction of the pharynx causes water to rise to the top of the gills. The gill lamella is flooded with water. Gaseous exchange occurs between blood and water in the lamellar capillary network. Oxygen from the water enters the blood and carbon dioxide from the blood enters the water. Oxygen enters the body through blood and carbon dioxide is released through water.

Ruhi fish have two gill chambers on either side of their pharynx. Each gill chamber is lined by conca. Each gill chamber has five gill arches. The first four gill arches bear one gill each. But the fifth gill arch has no gills. That is, there are four pairs (8) of gills in two gill chambers. Gills are the main respiratory organs of fish. Each gill arch has two gill rows. The inner edge of the gill arch expands to form the gill raker. Siddique Publications

Ruhi fish blood consists of two components. Plasma and blood cells. Plasma is colorless and composed of water, organic and inorganic components. There are two types of blood cells floating in plasma. Red blood cells and white blood cells. Red blood cells are oval, nucleated, rich in hemoglobin and red in color. White blood cells are amorphous, amoeboid, nucleated and colorless.

The veins that collect blood from different parts of the body and enter another organ and re-form the capillary network are called portal veins. It consists of hepatic portal and renal portal. Portal veins are:
(i) Caudal vein: The caudal vein enters the trunk from the tail and divides into two branches to form the renal portal vein. The renal portal vein brings blood from the digestive system to the liver.
(ii) Segmental vein: It collects blood from different parts of the body.
(iii) Transverse anastomosis veins: Right and left cardinal sinuses join with some transverse veins to form transverse anastomosis veins.
(iv) Sub clavian vein: It supplies blood directly from the thoracic fins to the sinus venosus.
(v) Hepatic veins: Two hepatic veins arise from the liver and bring blood to the sinus venosus.