Class Pisces general features and economic importance

Pisces: General features and classification up to orders; economic importance of fishes

 Class – Pisces

1.  The presence of gills for respiration is an important characteristic of fishes.
2.  Their skin is covered with scales/plates. 
3. They lay eggs [oviporous].
4. Some fishes are ovi-viviparous.
5. Presence of paired and unpaired fins.
6.  fertilization is internal. 
7. presence of air bladder act as an organ of buoyancy in some fishes.  
8. They obtain oxygen dissolved in water by using gills.
9. The body is streamlined, and a muscular tail is used for movement.
10. They are cold-blooded and their hearts have only two chambers.
11. Some fish skeletons are made entirely of cartilage [Chondrichthyes], such as sharks, 
12.  some with a skeleton made of both bone and cartilage [Osteichthyes].

CLASS: Chondrycthys / Elasmobranch

GENERAL CHARACTERS

1. They are marine animals with streamlined bodies and have cartilaginous endoskeletons. 
2. The mouth is located ventrally.
3. The notochord is persistent throughout life.
4. Gill slits are separate and without operculum (gill cover).
5. The skin is tough, containing minute placoid scales.
6. Their jaws are very powerful.
7. These animals are predaceous [shark].
8. Due to the absence of air bladder, they have to swim constantly to avoid sinking.
9. Heart is two-chambered (one auricle and one ventricle).
10. Some of them have electric organs (e.g., Torpedo) and some possess poison sting (e.g., Trygon).
11. They are cold-blooded (poikilothermous) animals, i.e., they lack the capacity to regulate their body temperature.
12. Sexes are separate. In males pelvic fins bear claspers.
13. They have internal fertilization and many of them are viviparous [give birth to young ones].
14. Examples: Scoliodon (Dogfish), Pristis (Sawfish), Carchaiodon (Great white shark), and Trygon (Stingray).

Class- Osteichthyes

General Characters

1. It includes both marine and freshwater fishes with bony endoskeletons.
2. Their body is streamlined. 
3. The mouth is mostly terminal.
4. They have four pairs of gills which are covered by an operculum on each side.
5. Skin is covered with cycloid/ctenoid scales.
6. The air bladder is present in the teleost of bony fishes which regulates buoyancy.
7. The heart is two-chambered (one auricle and one ventricle).
8. They are cold-blooded
9. Sexes are separate.
10. Fertilization is usually external.
11. They are mostly oviparous and development is direct.
12. Examples: Flying fish, Sea horse, Fighting fish, Angel fish etc.

DOG FISH / Scoliodaon

Phylum  Chordata               Presence o f notochord, pharyngeal gill slits and dorsal tubular nerve cord.

sub-phylum     Vertebrata -     Notochord replaced by vertebral column or backbone,

Class - Chondrichthyes        Presence of the notochord, pharyngeal gill slits, and dorsal tubular nerve cord.

Superclass - Gnathostomata -    Mouth with true jaws paired appendages present in the form of fins

or limbs.

Order - Pleurotremata     -       pectoral fins moderate, constricted at the base.present behind the eye.

Includes sharks with 5-7 pairs of lateral gill slits, body

Genus -            Scoliodan

Species-           sorrakowah

  Character 

•         Scoliodon is commonly called as dogfish.

•         Body divisible into head, trunk and tail.

•         Presence of 5 pairs of gill slits.

•         Presence of paired and unpaired fins.

•         Tail is slightly bends upward.

In male pelvic fin shows presence of claspers

STING RAY

Sting ray (Trygon)

Phylum  chordata                    Presence o f notochord, pharyngeal gill slits and dorsal tubular nerve cord.

sub-phylum     Vertebrata -     Notochord replaced by vertebral column or backbone,

Class - Chondricthyes or                     Presence of notochord, pharyngeal gill slits paired appendages present in

Elasmobranchii                        the form of fins

Order   Hypotremata               body is flat dorso-ventrally presence of gill slits. Pectoral fin is fused to side

of body.

  Character        

•          Trygon is commonly called as sting ray.

•         Body is dorso-ventrally flattened.

•         Body consists of head trunk and long tail.

•         Five pairs of gills slits on ventral side of body.

•         Mouth is ventral in position.

•         Pectoral fins are much larger fused with body on lateral side.

•         Tail is long whip like with poisonous sting . 

ELECTIC RAY

Electric ray (Torpedo)

Phylum  chordata                    Presence o f notochord, pharyngeal gill slits and dorsal tubular nerve cord.

sub-phylum     Vertebrata -     Notochord replaced by vertebral column or backbone,

Class - Chondricthyes or         Presence of notochord, pharyngeal gill slits paired appendages present Elasmobranchii                          in the form of fins

Order   Hypotremata               body is flat dorso-ventrally presence of gill slits. Pectoral fin is fused

to side of body.

Comments.

•         The body of electric ray is dorso-ventrally flattened.

•         Body is divisible into body proper and tail.

•         Presence of large oval eyes located on mid-dorsal side of the head.

•         Pectoral fins are attached to the side of body laterally.

•         Mouth is transverse and situated ventrally.

•         Tail is thick and short with two dorsal fins and a caudal fin.

•         Viviparous animal

•         Mouth is present on ventral side.

•         Presence of electric organs which generate electric current used to kill preys or enimies.

LABEO :

Phylum -    Chordata         Presence o f notochord, pharyngeal gill slits and dorsal tubular nerve cord.

sub-phylum     Vertebrata -     Notochord replaced by vertebral column or backbone,

Class –            Ostechthyes    Endoskeleton is bony 4 pairs of gills slits.  gill slits paired                               appendages present in the form of fins.

Order-             Cyprinifores    Air bladder connected to pharynx.  Presence of Weberian

                                                ossicles between air bladder.

Genus – Labeo

Species – rohita      

Comment.

•         Labeo is commonly called as rohu.

•         Body is spindle shaped.

•         Body divisible into head, trunk and tail.

•         Body shows presence of paired and unpaired fins.

•         Presence of 4 Paris of gill slits.

•         Gills are covered with operculum.

•         Body is covered with cycloid scales .

 CHARACTERS

1.      It is commonly found in the fresh water ponds, lakes and river.

2.      Body is divisible in to head, trunk and tail.

3.      Labeo is commonly called as rohu.

4.      Body is spindle shaped.

5.      Body divisible into head, trunk and tail.

6.      Body shows presence of paired and unpaired fins

7.      Head is depressed. It bears mouth; paired nostrils and paired eyes.

8.      Two small threads like sensory maxillary barbells are present at the corners of the mouth. Mouth without teeth.

9.      Dorsal, anal, caudal, paired pectoral and anal fin with soft fin rays present. Caudal fin is homocercal i.e. having two equal lobes.

10.  Body covered with overlapping cycloid scales.

EXOCOETUS 

Phylum -       Chordata     Presence o f notochord, pharyngeal gill slits and dorsal tubular nerve cord.

sub-phylum   Vertebrata -    Notochord replaced by vertebral column or backbone,

Class –           Ostechthyes    Endoskeleton is bony 4 pairs of gills slits.  gill slits paired                

                                               appendages present in the form of fins.

ORDER         : BELONIFORMES

CHARACTERS

1.      Commonly known as flying fish.

2.      Silvery white body and is divisible in to bead, trunk and tail.

3.      Body covered with overlapping cycloid scales.

4.      Mouth small with teeth in both jaws.

5.      Dorsal and anal tins are short but pectoral fins are exceptionally large spread like wings and makes gliding flights. It can glide over the surface of the water for about 400 meters.

6.      Tail homocercal.

SEA HORSE

Phylum -       Chordata      Presence o f notochord, pharyngeal gill slits and dorsal tubular nerve cord. 
sub-phylum    Vertebrata -     Notochord replaced by vertebral column or backbone,

Class –       Ostechthyes    Endoskeleton is bony 4 pairs of gills slits.  gill slits paired                

                                              appendages present in the form of fins.

ORDER                                        : SYNGNATHIFORMES

CHARACTERS

1.      Commonly called as sea horse because its anterior end likes the head of a horse.

2.      Mouth terminal, toothless and suctorial.

3.      Body is divisible into head, trunk and tail.

4.      Single dorsal fin, ventral and caudal fins are absent.

5.      Tail is prehensile.

6.      It swims vertically with it majestic snout.

7.      Sexually dimorphic, males with brood pouch on the belly for protecting eggs till hatching takes place

EEL FISH / ANGUILLA VULGARIS

Phylum -    Chordata         Presence o f notochord, pharyngeal gill slits and dorsal tubular nerve cord.

sub-phylum           Vertebrata -     Notochord replaced by vertebral column or backbone,

Class –                   Ostechthyes    Endoskeleton is bony 4 pairs of gills slits.  gill slits paired                

                                                      appendages present in the form of fins.

ORDER                                        : ANGUlLIFORMES

 CHARACTERS

1.      Commonly known as eel fish. It is fresh water fish and can live several hours outside the water.

2.      Body is slender elongated and snake like. It is divisible into head, trunk and tail.

3.      Head contains a mouth, eyes, and nostrils. On each side, the operculum covers the gill slits.

4.      Dorsal fin, anal fin and caudal fin are joined together forming a continuous fin. Small pectoral fins behind the operculum.

5.      They have a peculiar breeding habit. 

 

Economic Importance of Fishes  

    Fish unsuitable for human consumption is often discarded during processing. These and such species have little market value from important raw materials for a fishery by-product industry.  Fish is a highly perishable food material because of its moisture and nutrient contents, and spoilable begins as soon as fish dies, it is the result of a series of complicated chemical reactions taking place in a dead fish, mainly by enzymes and bacteria. These are either thrown back into the sea immediately after their catch or utilized wholly or partly as manure.

Fishes are largely consumed as a source of food material all over the world because of their nutritional value. Fishes in India are mostly consumed fresh and some are preserved or dried for further use as food.  The major source of fish is the oceans which fulfill the need for food for the growing population.  Most of the time waste fish are thrown back into the sea just immediately after a catch or used wholly or partly as manure.    Fishes are highly perishable food material because of the presence of moisture and nutrients, fishes get spoil soon after death. These are unutilized for the preparation of many byproducts of human and industrial use. It would enhance the economy of the country by selling them.

Some of the important fish byproducts are    as follows 

 

                                       

1.     Fish protein concentrate

2.     Fish flour

3.     Fish glue

4.     Fish skin

5.     Fish liver oil

6.     Body Oil

7.     Fish meal

8.     Gelatin

9.     Insulin

10. Fish fins

11. Isinglass

12.  Fish guano

13. Fish manure

 

 

1. Fish protein concentrate – It is a stable protein concentrate prepared from whole fish. It is a colorless and odorless powder with high nutritional value for human use.  It contains protein and minerals. It is also known as fish flour or edible fish meal.

2. Fish flour -  Fish flour is a superior quality of fish meal, which is used for human intake. It can be mixed with another foodstuff such as wheat flour for enriching the nutritive value of bread, biscuits, cakes, etc.

3. Fish glue or adhesive  - fish glue is prepared from the skin, fins, and bones of fish.  which are washed, crushed, and cooked in large vessels for 6-10 hours with acetic acid. The liquid is separated and concentrated to form fish glue which is used as an adhesive for fixing wood, paper and leather. bookbinding, labels, paper boxes etc.

4. Fish skin- the skin of a shark is used for the preparation of polish paper which is called as shagreen used in furniture polishing.

5. Fish liver oil – it has huge content of vitamins A and D used to prevent deficiency or cure rickets, xerophthalmia, impaired vision and eye defects, abnor¬malities of skin, mucous membranes, and vertebrae in the body.

6. Body oil –  It is used in the manufacture of cosmetics, lubricants, candles and cutting oils, printing inks, water-proof preparations, and cheaper-grade toilet soap.  Body oil is used for coating the surface of boats for longer preservation.  Body oil is used for coating the surface of boats for longer preservation.

7. Fish meal-  It is excellent poultry and animal feed as the highly nutritive product contains all the essential amino acids. Fish meal is good for all classes of livestock. It increases milk and egg production. As it is rich in calcium, phosphorus, iodine, and a rich variety of vitamins promotes the building of tissue and bones used for the healthy growth of growing cattle. Waste fish meal mixed with rice bran and vitamins forms an excellent feed in aquaculture.

8. Gelatin – gelatin is extracted from bones and skin of fishes. Gelatin is a rich source of lysine and methionine. It is used in the food industry as a gelling, stabilizing, emulsifying, dispersing or thickening agent.

9. Insulin: Insulin is a hormone used for correcting the condition called diabetes mellitus in humans. Fish insulin is more stable as it is not subjected to decomposition by protein-splitting enzymes of the pancreas.

10.        Fish fins –The dried fins of sharks are exported to China where they have great demand for the preparation of soups.

11.        Isinglass: The air bladder of some fishes such as catfish, eels, carp, seabass etc. are used for the preparation of isinglass.  Isinglass reduces the suspended solids in beer and increases filtration. It can also be used as an adhesive base and in the sweet product, it is used for the preparation of ink and also used as an effective adhesive for glass, pottery, and leather. 

12.        Guano:  is the byproduct from body oil extraction industries. It is nothing but the dried waste left after the extraction of body oil.  fish guano is more effective as it contains a large quantity of nitrogen and phosphoric acid. Fish guano is also used as fish manure.

 

13.        Fish Manure:  Fish manure and guano are the lower quality of the fish meal. It is not fit for animal consumption. Fish ma¬nure is a by-product of the curing yards, fish glue industries, and oil extraction plants, where waste or spoilt fish have been used. The fishes which are spoilt and unhealthy for use as food is used for the preparation of fish manure. Fish manure contains nitrogen and phosphates which are useful for agricultural use.