Fisheries

A large number of the world population is dependent on fish, fish products, and other aquatic animals for food. Fish and other seafood are rich in protein and polyunsaturated fatty acids (PUFA). In some parts of the world, people prefer eating fish than meat. Today fishery is considered an industry. It is concerned with catching, processing, or selling fish, and other aquatic animals like prawn, crab, lobster, edible oyster, etc. Basically, there are two types of fisheries, namely Inland fishery and Marine fishery.

Inland Fishery

Inland fishery is the rearing of fish and other aquatic animals in freshwaters like rivers, ponds, lakes, etc. Generally, fish like Catla, Rohu, Labeo, Common Carp, Catfish, and freshwater prawns like Palaemon are cultivated in freshwater fisheries.

Marine Fishery

Marine fishery means catching and processing of marine animals like fishes, oysters, crabs, prawns, etc. 

Fisheries provide income and employment to millions of fishermen and farmers living in coastal areas. Nowadays in order to meet the high demand for fish and other seafood, farmers have started cultivating them in artificial ponds. This type of fisheries is called aquaculture. Here fishes are cultivated in large tanks in a controlled environment. The fishes are provided food in the form of crushed vegetables etc. The fishes are regularly sampled and are checked for diseases and infections. If the infection is found in fishes the group is isolated and medicine is administered in the water.

Fish diseases

Here are some of the common diseases that affect fishes.

Disease	Pathogen
Gill Rot	Fungus-Branchiomyces sanguinis
Tail and fin rot	Bacterium-Pseudomonas, Aeromonas
Dropsy	Bacterium-Aeromonas
Myxosporidiosis	Protozoan-Myxobolus
Arguilosis	Crustacean-Carp Lice-Argalis
Helminth	Flatworm-Gyrodactylus

Cultivating both fishes and prawns together is called aquaculture whereas cultivating only fishes is called pisciculture. Aquaculture and pisciculture increase the availability of seafood extensively. This dramatic increase in seafood production was called the blue revolution.

Fish preservation

Fish is a highly perishable food and tends to decay soon, therefore, it should be preserved immediately after being caught to increase its shelf life. There are various methods of fish preservation to increase their shelf life:

Chilling: in this method, the fish is covered with ice. This slows down the decay of fishes. However, for a long time period, the fishes are usually getting decayed. Hence, it is not very effective for long-distance transport.

Freezing: in this method the fish and covered with a mixture of Ice and salt. Here also, if the fish is kept for long periods, the fish tends to become rancid.

Deep freezing: this process keeps the fish fresh for a longer period of time.

Salting: in this process, the gut of the fish is taken out, scarred, and then rolled in salt.

Sun-drying: in this process, the fish after being caught is allowed to dry under the heat of the sun for a few days till the moisture evaporates. This dehydrated fish can be stored and used for many days.

Smoking: in this process, the fishes are hot smoked in an oven having a temperature of 60-110 0C for 4-12 hours to kill the non-sporulating bacteria.

Chemical preservation: in this method of preservation chemicals like Hydrogen Peroxide, potassium, or sodium nitrate, vinegar, ascorbic acid, etc. are used to preserve the fish.

Canning: in this process, the fish is first cleaned and boneless pieces are then cut, cooked, and sealed in cans for supply to distant places.

Economic importance 

Fishes are used as food and are a good source of protein, lipids, vitamins, and iodine. The total protein content in fishes is 19.3 % and in prawn is 26.8%. But liquid content is high in fish but less than prawn. Fish and other seafood are rich in iodine and other minerals. Fish liver oil like Shark liver oil and cod liver oil are a good source of vitamin A and D and is used in medicines. Oils derived from other parts of the fish body are used in paints and soaps. Isinglass obtained from the swim bladder of fishes, is used in clarifying vinegar, beer, and wines. Shark skin is abrasive and is called shagreen. It is used in smoothening services for polishing as well as covering certain articles. Certain carnivorous fishes like Gambusia and Guppy fish helps in controlling diseases as they feed on mosquito larvae. Fish waste like fins, tails, and bones, etc. are rich in calcium, protein, Phosphorus, and other substances. These materials are ground into a powder and used as poultry feed and also as manure in grape gardens, coffee, and tea plants. Many fishes are dressed, cooked, and dried. These are then made into a fine powder called a fish meal. It is not fit for human consumption but it is used as a food supplement to prawns, poultry, pigs, etc.