The system through which blood circulates in the body is called circulatory system. The blood circulation of cotton fish is closed. It shows unicyclic or unicyclic blood circulation. Circulation in which O2-rich or CO2-rich blood circulates through the heart in one cycle is called unicyclic or unicyclic circulation. The circulatory system of roe fish consists of four parts. Heart, Arterial System, Venous System and Blood. Dr. Siddiq Publications

Ruhi fish have even/paired and odd/unpaired fins. Each fin has bony fin rays. It has five types of fins.
1. Pectoral fins: Kanko has a pair of pectoral fins on its back. It has 16-19 fin rays. It helps the fish rise to the top of the water.
2. Surface fins: There is a surface fin on the surface of the body. It has 14-16 fin rays. It helps the fish to turn and stop.
3. Class fins: There is a pair of class fins in the middle part of the body. It has 7-9 fin rays. This helps the fish move up and down and stop.
4. Anal fins: There is an anal fin behind the anus on the base of the body. It has 4-7 fin rays. It helps keep the fish stable.
5. Caudal Fin: There is a caudal fin behind the tail. It is bisected and homocircular. It has 19 fin rays. It acts as the main locomotor organ of the fish. Dr. Siddiq Publications

Cycloid cysts are round or oval in appearance and silvery white in color. At its center is the focus or nucleus. It has two types of lines. Circulus line and annulus line. Menstrual line of Aish is called Circulus line. It is short and vague. The annual line of gravity is called annulus line. It’s big and clear. One annulus line is formed every year in a cycloid scale. The month can be determined by calculating the circle line and the year by calculating the annulus line. If there is 1 annulus line in Aish, 1 year is calculated, if there are 2, 2 years. Thus the age of the fish is determined by counting the annulus and circulus lines. Ruhi fish live for a maximum of 10 years. Therefore, there can be maximum 10 annulus lines in its scales. Dr. Siddiq Publications

Fish scales that are round or oval, with growth lines and smooth edges are called cycloid scales. Chemically, fibers are composed of calcium and collagen fibers. During the spring and summer, there is more growth of anise. Cycloid Anish consists of three parts. The parts are-
1. Foreground : The front part of scale is called Foreground. It resides in the inner part of the body and in pockets of the dermis. The anterior fibrous connective tissue is constructed of banana. The longitudinal grooves seen in the tip are called radii. Dr. Siddiq Publications
2. Backyard : The exposed part on the outer side of the anish is called Backyard. It is made of dentin.
3. Side Area: The part on either side of the Aish is called side area.

1. Scales act as the main protective organ of fish.
2. It reduces the water barrier during fish movement.
3. The mucus present in the scales destroys the germs and makes the fish immune to diseases.
4. Lateral waves sense the frequency of the water.
5. Anim plays a role in determining the taxonomy, age, growth rate, life history etc. of fish.

Fish body which is round or oval, covered with hard and thin shell is called fish. The main defense organ of fish is scales. It originates from the dermal layer of the skin. Different types of fish scales are cycloid scales, placoid scales, ganoid scales, tinoid scales etc.

1. By this the fish can determine the pH of the water.
2. It helps the fish to determine the depth of the water.
3. With the help of this line, the fish can sense the turbidity of the water.
4. Receives stimuli from the external environment.
5. It helps to escape from enemies.

A fish has two lateral lines running from tip to tail on either side of its body. It is called sensory side line because it contains sensory cells. It works as a chemoreceptor or chemical receiver.

Ruhi fish looks long, squishy and mace-shaped. Such structure is called streamlined. It is silvery white in color. They are over three feet tall and can weigh 20-25 kg. The body of roe fish consists of three parts. Head, body and tail
1. Head: The part from the tip of the body to the neck is called the head. The surface of the head is convex, smooth and free from scales. A semi-circular mouth hole is located just below the head. The mouth is surrounded by fleshy lips. On either side of the mouth opening are thread-like sensory maxillary barbels. There are two eyes on either side of the head. There is no pallava in the eyes. There is one nostril in front of the eyes. Each side has a large movable kanko. Beneath the kanko are four comb-like gills. At the free end of the conch there is a thin bronchiostigmal membrane.
2. Body: The part from the back of the fin to the anus is called the body. It is the largest part of the body. On either side of the body there are two lateral lines from tip to tail. It is called sensory side line because it contains sensory cells. It contains numerous lateral line organs or neuromasts. The body of ray fish has even and odd fins. These are a pair of pectoral fins, a pair of pelvic fins, a large dorsal fin and an anal fin. The stem is covered with thin cycloid scales. There are three tiny pores on the base of the body. Anus, genitals and rectal pores. Dr. Siddiq Publications
3. Tail: The end of the body from the anus is called the tail. At the tip of the tail is a homocircular caudal fin. It is divided into two parts. Super-symmetric and Semi-symmetric. The tail has 6 fins. Tail fin is the only moving part of fish.

A large amount of cotton is found in lakes, rivers, haor-baor, canal-bil, ponds etc. in Bangladesh, India and Myanmar. They live in the middle layer of water. Roe fish does not survive below 14 degrees Celsius. The best temperature for its growth is 30-32 degrees Celsius.
Ruhi fish are omnivores. Caterpillars feed on zooplankton and Angulipona feed on phytoplankton. Adult fish feed on algae and soft plants. The food of commercially cultivated cotton fish is rice bran, wheat husk, mustard husk, other supplementary food etc.