Fisheries: Types of Fisheries and it Economical Importance

Fisheries: Types of Fisheries and it Economical Importance! Fish are aquatic, cold blooded and craniate vertebrates belonging to the super class Pisces under phylum Chordata.

Fishery is a kind of industry which is concerned with the catching, processing or selling of fish, shellfish (molluscs, each has a shell in two halves, used for food, e.g., mussels, oysters, etc.) and crustaceans.

Economic Importance of Fish:

(i) Fish as food:

The fish flesh is an excellent source of protein, has very little fat, carries a good amount of minerals and vitamins A and D and rich in iodine. Above all man can digest it easily. Some important edible fish of India are given in the Table 9.7 & 9.8.

(ii) Fish for controlling diseases:

Diseases like malaria, yellow fever and other dreadful diseases that are spread through mosquitoes can be controlled. Larvivorous fish eat larva of mosquito. The important larvivorous fish are Gambusia, Panchax, Haplochitus, Trichogaster, etc.

(iii) Scientific value:

Some fish like the lung fish are of zoological importance because of their discontinuous distribution and anatomical features.

(iv) Aesthetic value:

A large number of fish are cultured in aquarium for their beauty and graceful movements. The important aquarium fish are Macropodus, Trichogaster, Carassinus (gold fish) and Pterophyllum (angel fish).

(v) Fishery Bye-products:

(a) Fish oil:

It is extracted from the liver of the sharks, sawfishes, skates and rays and has medicinal value. These mainly include cod liver oil and shark liver oil.

(b) Fish Manure:

The fish waste after the extraction of oil, is used as fertilizers,

(c) Fish Glue:

It is a sticky product, obtained from the skin of the cod and is used as gum.

(d) Isinglass:

It is a gelatinous substance, obtained from the air bladder of perches, Indian Salmons and cat fish used in the preparation of special cement and in the clarification of wine and beer,

(e) Shagreen:

The skin of sharks and rays, which has pointed and sharp placoid scales are used in polishing the wood and other materials. It is also used for covering the jewellery boxes and swords,

(f) Leather:

A highly durable type of leather is prepared from the skin of sharks and rays,

(g) Artificial pearls:

The silvery boney scales of cypnmids (a type of fish) are used in the manufacture of artificial pearls especially in France.

(vi) Employment:

Development of fishing industry generates more employment opportu­nities.

(vii) Source of Income:

The fishing industry has brought a lot of income to the farmers in particular and the country in general. Now we can talk about “Blue Revolution” (fish production) on the same lines as ‘Green Revolution’ (for producing enough food for all).

Types of Fisheries:

There are two main types of fisheries: Inland fisheries and marine fisheries.

Inland or Fresh Water Fisheries:

Inland fishery deals with the fishery aspects of waters other than marine water. Potentially, the vast and varied inland fishery resources of India are one of the richest in the world. They pertain to two types of waters, namely, the fresh and the brackish. The former includes the country’s great river systems, an extensive network of irrigation canals, reservoirs, lakes, tanks, ponds, etc.

The estuaries, lagoons and mangrove swamps constitute the brackish type of water. In pisciculture (culture fisheries), which generally pertains to small water bodies, the fish seed has to be sown, tended, nursed, reared and finally harvested when grown to table size. In the case of capture fisheries, which pertain to the rivers, estuaries, large reservoirs, as well as big lakes, man has only to reap without having to sow some important edible fresh waterfishes of India are given in the table 9.7.

Table 9.7. Important Edible Fresh Water Fishes of India:

Types of Breeding:

According to the mode of breeding there are two categories, natural breeding and induced breeding.

(i) Natural Breeding (Bundh breeding):

The natural bundhs are special types of ponds where natural water resource conditions are managed for the breeding of culturable fish. These bundhs are constructed in large low-lying areas to accumulate large quantity of rain water. These bundhs are having an outlet for the exit of excess rain water.

(ii) Induced Breeding:

In artificial method of fertilization ova from the females and the sperms from the males are taken out by artificial mechanical process and the eggs are got fertilized by the sperms. Different methods are used for induced breeding. Here induced breeding by hormones method is briefly described. The gonadotropin hormone (FSH and LH) secreted by pituitary gland influences the maturation of gonads and spawning in fishes. In India, Khan (1938) successfully induced Cirrhinus mrigala to spawn by injecting mammalian pituitary hormone.

(iii) Composite Fish Farming:

It is found that if few selected species of fish are stocked together in proper proportion in a pond, total production of fish is increased many times. This mixed farming is called composite farming. It has some advantage-compatible species do not harm each other, all available areas are fully utilised, no competition among different species is found and fish may have beneficial effect on each other. Catla catla, Labeo-rohita and Cirrhina mrigala are surface feeder, column feeder and bottom feeder respectively and are used for composite farming.

Marine Fisheries:

Marine fishery deals with the fishery aspects of the sea water or ocean.

Table 9.8. Important Edible Marine Fish of India:

Hilsa migrates from the sea to the river for breeding. Dr. Hora studied the migration of Hilsa.

Fish Diseases Caused by Parasites and Pathogens:

1. Bacterial Diseases:

Two bacterial diseases are very important.

(i) Abdominal dropsy of Carps is caused by Aeromonas punctuata.

(ii) Furunculoris of Salmons and trout’s is caused by Aeromonas salminicida.

2. Viral Diseases:

Economically most important is the viral haemorrhage septicaemia (VHS) of rainbow trouts.

3. Protozoan Diseases:

Main protozoan diseases are caused by Costia, Myxobolus and Trypanosoma.

4. Fungal Diseases:

The gill rot (branchyomyces) of carps involves the attack of Saprolegnia on the gills of carps.

5. Worm Diseases:

Worms of four groups are parasites on fish. The flatworms (trematodes), tapeworms (cestodes), round worms (nematodes) and thorny-headed worms (acanthocephalans).

6. Common Ectoparasites:

Two ectoparasites of fish are most important, the fish lice (Argulus, Lernaea and Ergasilus) and the fish leech (Piscicold). Both parasites weaken fish by feeding on its blood.